latest research on e cigarettes

• Open access
• Published: 18 May 2021

An updated overview of e-cigarette impact on human health

• Patrice Marques   ORCID: orcid.org/0000-0003-0465-1727 1 , 2 ,
• Laura Piqueras   ORCID: orcid.org/0000-0001-8010-5168 1 , 2 , 3 &
• Maria-Jesus Sanz   ORCID: orcid.org/0000-0002-8885-294X 1 , 2 , 3  

Respiratory Research volume  22 , Article number:  151 ( 2021 ) Cite this article

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The electronic cigarette ( e-cigarette ), for many considered as a safe alternative to conventional cigarettes, has revolutionised the tobacco industry in the last decades. In e-cigarettes , tobacco combustion is replaced by e-liquid heating, leading some manufacturers to propose that e-cigarettes have less harmful respiratory effects than tobacco consumption. Other innovative features such as the adjustment of nicotine content and the choice of pleasant flavours have won over many users. Nevertheless, the safety of e-cigarette consumption and its potential as a smoking cessation method remain controversial due to limited evidence. Moreover, it has been reported that the heating process itself can lead to the formation of new decomposition compounds of questionable toxicity. Numerous in vivo and in vitro studies have been performed to better understand the impact of these new inhalable compounds on human health. Results of toxicological analyses suggest that e-cigarettes can be safer than conventional cigarettes, although harmful effects from short-term e-cigarette use have been described. Worryingly, the potential long-term effects of e-cigarette consumption have been scarcely investigated. In this review, we take stock of the main findings in this field and their consequences for human health including coronavirus disease 2019 (COVID-19).

Electronic nicotine dispensing systems (ENDS), commonly known as electronic cigarettes or e-cigarettes , have been popularly considered a less harmful alternative to conventional cigarette smoking since they first appeared on the market more than a decade ago. E-cigarettes are electronic devices, essentially consisting of a cartridge, filled with an e-liquid, a heating element/atomiser necessary to heat the e-liquid to create a vapour that can be inhaled through a mouthpiece, and a rechargeable battery (Fig.  1 ) [ 1 , 2 ]. Both the electronic devices and the different e-liquids are easily available in shops or online stores.

Effect of the heating process on aerosol composition. Main harmful effects documented. Several compounds detected in e-cigarette aerosols are not present in e-liquid s and the device material also seems to contribute to the presence of metal and silicate particles in the aerosols. The heating conditions especially on humectants, flavourings and the low-quality material used have been identified as the generator of the new compounds in aerosols. Some compounds generated from humectants (propylene glycol and glycerol) and flavourings, have been associated with clear airways impact, inflammation, impairment of cardiovascular function and toxicity. In addition, some of them are carcinogens or potential carcinogens

The e-liquid typically contains humectants and flavourings, with or without nicotine; once vapourised by the atomiser, the aerosol (vapour) provides a sensation similar to tobacco smoking, but purportedly without harmful effects [ 3 ]. However, it has been reported that the heating process can lead to the generation of new decomposition compounds that may be hazardous [ 4 , 5 ]. The levels of nicotine, which is the key addictive component of tobacco, can also vary between the commercially available e-liquids, and even nicotine-free options are available. For this particular reason, e-cigarettes are often viewed as a smoking cessation tool, given that those with nicotine can prevent smoking craving, yet this idea has not been fully demonstrated [ 2 , 6 , 7 ].

Because e-cigarettes are combustion-free, and because most of the damaging and well-known effects of tobacco are derived from this reaction, there is a common and widely spread assumption that e-cigarette consumption or “vaping” is safer than conventional cigarette smoking. However, are they risk-free? Is there sufficient toxicological data on all the components employed in e-liquids ? Do we really know the composition of the inhaled vapour during the heating process and its impact on health? Can e-cigarettes be used to curb tobacco use? Do their consumption impact on coronavirus disease 2019 (COVID-19)? In the present review, we have attempted to clarify these questions based on the existing scientific literature, and we have compiled new insights related with the toxicity derived from the use of these devices.

Effect of e-cigarette vapour versus conventional cigarette exposure: in vivo and in vitro effects

Numerous studies have been performed to evaluate the safety/toxicity of e-cigarette use both in vivo and in in vitro cell culture.

One of the first studies in humans involved the analysis of 9 volunteers that consumed e-cigarettes , with or without nicotine, in a ventilated room for 2 h [ 8 ]. Pollutants in indoor air, exhaled nitric oxide (NO) and urinary metabolite profiles were analysed. The results of this acute experiment revealed that e-cigarettes are not emission-free, and ultrafine particles formed from propylene glycol (PG) could be detected in the lungs. The study also suggested that the presence of nicotine in e-cigarettes increased the levels of NO exhaled from consumers and provoked marked airway inflammation; however, no differences were found in the levels of exhaled carbon monoxide (CO), an oxidative stress marker, before and after e-cigarette consumption [ 8 ]. A more recent human study detected significantly higher levels of metabolites of hazardous compounds including benzene, ethylene oxide, acrylonitrile, acrolein and acrylamide in the urine of adolescent dual users ( e-cigarettes and conventional tobacco consumers) than in adolescent e-cigarette -only users (Table 1 ) [ 9 ]. Moreover, the urine levels of metabolites of acrylonitrile, acrolein, propylene oxide, acrylamide and crotonaldehyde, all of which are detrimental for human health, were significantly higher in e-cigarette -only users than in non-smoker controls, reaching up to twice the registered values of those from non-smoker subjects (Table 1 ) [ 9 ]. In line with these observations, dysregulation of lung homeostasis has been documented in non-smokers subjected to acute inhalation of e-cigarette aerosols [ 10 ].

Little is known about the effect of vaping on the immune system. Interestingly, both traditional and e-cigarette consumption by non-smokers was found to provoke short-term effects on platelet function, increasing platelet activation (levels of soluble CD40 ligand and the adhesion molecule P-selectin) and platelet aggregation, although to a lesser extent with e-cigarettes [ 11 ]. As found with platelets, the exposure of neutrophils to e-cigarette aerosol resulted in increased CD11b and CD66b expression being both markers of neutrophil activation [ 12 ]. Additionally, increased oxidative stress, vascular endothelial damage, impaired endothelial function, and changes in vascular tone have all been reported in different human studies on vaping [ 13 , 14 , 15 , 16 , 17 ]. In this context, it is widely accepted that platelet and leukocyte activation as well as endothelial dysfunction are associated with atherogenesis and cardiovascular morbidity [ 18 , 19 ]. In line with these observations the potential association of daily e-cigarettes consumption and the increased risk of myocardial infarction remains controversial but benefits may occur when switching from tobacco to chronic e-cigarette use in blood pressure regulation, endothelial function and vascular stiffness (reviewed in [ 20 ]). Nevertheless, whether or not e-cigarette vaping has cardiovascular consequences requires further investigation.

More recently, in August 2019, the US Centers for Disease Control and Prevention (CDC) declared an outbreak of the e-cigarette or vaping product use-associated lung injury (EVALI) which caused several deaths in young population (reviewed in [ 20 ]). Indeed, computed tomography (CT scan) revealed local inflammation that impaired gas exchange caused by aerosolised oils from e-cigarettes [ 21 ]. However, most of the reported cases of lung injury were associated with use of e-cigarettes for tetrahydrocannabinol (THC) consumption as well as vitamin E additives [ 20 ] and not necessarily attributable to other e-cigarette components.

On the other hand, in a comparative study of mice subjected to either lab air, e-cigarette aerosol or cigarette smoke (CS) for 3 days (6 h-exposure per day), those exposed to e-cigarette aerosols showed significant increases in interleukin (IL)-6 but normal lung parenchyma with no evidence of apoptotic activity or elevations in IL-1β or tumour necrosis factor-α (TNFα) [ 22 ]. By contrast, animals exposed to CS showed lung inflammatory cell infiltration and elevations in inflammatory marker expression such as IL-6, IL-1β and TNFα [ 22 ]. Beyond airway disease, exposure to aerosols from e-liquids with or without nicotine has also been also associated with neurotoxicity in an early-life murine model [ 23 ].

Results from in vitro studies are in general agreement with the limited number of in vivo studies. For example, in an analysis using primary human umbilical vein endothelial cells (HUVEC) exposed to 11 commercially-available vapours, 5 were found to be acutely cytotoxic, and only 3 of those contained nicotine [ 24 ]. In addition, 5 of the 11 vapours tested (including 4 that were cytotoxic) reduced HUVEC proliferation and one of them increased the production of intracellular reactive oxygen species (ROS) [ 24 ]. Three of the most cytotoxic vapours—with effects similar to those of conventional high-nicotine CS extracts—also caused comparable morphological changes [ 24 ]. Endothelial cell migration is an important mechanism of vascular repair than can be disrupted in smokers due to endothelial dysfunction [ 25 , 26 ]. In a comparative study of CS and e-cigarette aerosols, Taylor et al . found that exposure of HUVEC to e-cigarette aqueous extracts for 20 h did not affect migration in a scratch wound assay [ 27 ], whereas equivalent cells exposed to CS extract showed a significant inhibition in migration that was concentration dependent [ 27 ].

In cultured human airway epithelial cells, both e-cigarette aerosol and CS extract induced IL-8/CXCL8 (neutrophil chemoattractant) release [ 28 ]. In contrast, while CS extract reduced epithelial barrier integrity (determined by the translocation of dextran from the apical to the basolateral side of the cell layer), e-cigarette aerosol did not, suggesting that only CS extract negatively affected host defence [ 28 ]. Moreover, Higham et al . also found that e-cigarette aerosol caused IL-8/CXCL8 and matrix metallopeptidase 9 (MMP-9) release together with enhanced activity of elastase from neutrophils [ 12 ] which might facilitate neutrophil migration to the site of inflammation [ 12 ].

In a comparative study, repeated exposure of human gingival fibroblasts to CS condensate or to nicotine-rich or nicotine-free e-vapour condensates led to alterations in morphology, suppression of proliferation and induction of apoptosis, with changes in all three parameters greater in cells exposed to CS condensate [ 29 ]. Likewise, both e-cigarette aerosol and CS extract increased cell death in adenocarcinomic human alveolar basal epithelial cells (A549 cells), and again the effect was more damaging with CS extract than with e-cigarette aerosol (detrimental effects found at 2 mg/mL of CS extract vs. 64 mg/mL of e-cigarette extract) [ 22 ], which is in agreement with another study examining battery output voltage and cytotoxicity [ 30 ].

All this evidence would suggest that e-cigarettes are potentially less harmful than conventional cigarettes (Fig.  2 ) [ 11 , 14 , 22 , 24 , 27 , 28 , 29 ]. Importantly, however, most of these studies have investigated only short-term effects [ 10 , 14 , 15 , 22 , 27 , 28 , 29 , 31 , 32 ], and the long-term effects of e-cigarette consumption on human health are still unclear and require further study.

Comparison of the degree of harmful effects documented from e-cigarette and conventional cigarette consumption. Human studies, in vivo mice exposure and in vitro studies. All of these effects from e-cigarettes were documented to be lower than those exerted by conventional cigarettes, which may suggest that e-cigarette consumption could be a safer option than conventional tobacco smoking but not a clear safe choice

Consequences of nicotine content

Beyond flavour, one of the major issues in the e-liquid market is the range of nicotine content available. Depending on the manufacturer, the concentration of this alkaloid can be presented as low , medium or high , or expressed as mg/mL or as a percentage (% v/v). The concentrations range from 0 (0%, nicotine-free option) to 20 mg/mL (2.0%)—the maximum nicotine threshold according to directive 2014/40/EU of the European Parliament and the European Union Council [ 33 , 34 ]. Despite this normative, however, some commercial e-liquids have nicotine concentrations close to 54 mg/mL [ 35 ], much higher than the limits established by the European Union.

The mislabelling of nicotine content in e-liquids has been previously addressed [ 8 , 34 ]. For instance, gas chromatography with a flame ionisation detector (GC-FID) revealed inconsistencies in the nicotine content with respect to the manufacturer´s declaration (average of 22 ± 0.8 mg/mL vs. 18 mg/mL) [ 8 ], which equates to a content ~ 22% higher than that indicated in the product label. Of note, several studies have detected nicotine in those e-liquids labelled as nicotine-free [ 5 , 35 , 36 ]. One study detected the presence of nicotine (0.11–6.90 mg/mL) in 5 of 23 nicotine-free labelled e-liquids by nuclear magnetic resonance spectroscopy [ 35 ], and another study found nicotine (average 8.9 mg/mL) in 13.6% (17/125) of the nicotine-free e-liquids as analysed by high performance liquid chromatography (HPLC) [ 36 ]. Among the 17 samples tested in this latter study 14 were identified to be counterfeit or suspected counterfeit. A third study detected nicotine in 7 of 10 nicotine-free refills, although the concentrations were lower than those identified in the previous analyses (0.1–15 µg/mL) [ 5 ]. Not only is there evidence of mislabelling of nicotine content among refills labelled as nicotine-free, but there also seems to be a history of poor labelling accuracy in nicotine-containing e-liquids [ 37 , 38 ].

A comparison of the serum levels of nicotine from e-cigarette or conventional cigarette consumption has been recently reported [ 39 ]. Participants took one vape from an e-cigarette , with at least 12 mg/mL of nicotine, or inhaled a conventional cigarette, every 20 s for 10 min. Blood samples were collected 1, 2, 4, 6, 8, 10, 12 and 15 min after the first puff, and nicotine serum levels were measured by liquid chromatography-mass spectrometry (LC–MS). The results revealed higher serum levels of nicotine in the conventional CS group than in the e-cigarette group (25.9 ± 16.7 ng/mL vs. 11.5 ± 9.8 ng/mL). However, e-cigarettes containing 20 mg/mL of nicotine are more equivalent to normal cigarettes, based on the delivery of approximately 1 mg of nicotine every 5 min [ 40 ].

In this line, a study compared the acute impact of CS vs. e-cigarette vaping with equivalent nicotine content in healthy smokers and non-smokers. Both increased markers of oxidative stress and decreased NO bioavailability, flow-mediated dilation, and vitamin E levels showing no significant differences between tobacco and e-cigarette exposure (reviewed in [ 20 ]). Inasmuch, short-term e-cigarette use in healthy smokers resulted in marked impairment of endothelial function and an increase in arterial stiffness (reviewed in [ 20 ]). Similar effects on endothelial dysfunction and arterial stiffness were found in animals when they were exposed to e-cigarette vapor either for several days or chronically (reviewed in [ 20 ]). In contrast, other studies found acute microvascular endothelial dysfunction, increased oxidative stress and arterial stiffness in smokers after exposure to e-cigarettes with nicotine, but not after e-cigarettes without nicotine (reviewed in [ 20 ]). In women smokers, a study found a significant difference in stiffness after smoking just one tobacco cigarette, but not after use of e-cigarettes (reviewed in [ 20 ]).

It is well known that nicotine is extremely addictive and has a multitude of harmful effects. Nicotine has significant biologic activity and adversely affects several physiological systems including the cardiovascular, respiratory, immunological and reproductive systems, and can also compromise lung and kidney function [ 41 ]. Recently, a sub-chronic whole-body exposure of e-liquid (2 h/day, 5 days/week, 30 days) containing PG alone or PG with nicotine (25 mg/mL) to wild type (WT) animals or knockout (KO) mice in α7 nicotinic acetylcholine receptor (nAChRα7-KO) revealed a partly nAChRα7-dependent lung inflammation [ 42 ]. While sub-chronic exposure to PG/nicotine promote nAChRα7-dependent increased levels of different cytokines and chemokines in the bronchoalveolar lavage fluid (BALF) such as IL-1α, IL-2, IL-9, interferon γ (IFNγ), granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1/CCL2) and regulated on activation, normal T cell expressed and secreted (RANTES/CCL5), the enhanced levels of IL-1β, IL-5 and TNFα were nAChRα7 independent. In general, most of the cytokines detected in BALF were significantly increased in WT mice exposed to PG with nicotine compared to PG alone or air control [ 42 ]. Some of these effects were found to be through nicotine activation of NF-κB signalling albeit in females but not in males. In addition, PG with nicotine caused increased macrophage and CD4 + /CD8 + T-lymphocytes cell counts in BALF compared to air control, but these effects were ameliorated when animals were sub-chronically exposed to PG alone [ 42 ].

Of note, another study indicated that although RANTES/CCL5 and CCR1 mRNA were upregulated in flavour/nicotine-containing e-cigarette users, vaping flavour and nicotine-less e-cigarettes did not significantly dysregulate cytokine and inflammasome activation [ 43 ].

In addition to its toxicological effects on foetus development, nicotine can disrupt brain development in adolescents and young adults [ 44 , 45 , 46 ]. Several studies have also suggested that nicotine is potentially carcinogenic (reviewed in [ 41 ]), but more work is needed to prove its carcinogenicity independently of the combustion products of tobacco [ 47 ]. In this latter regard, no differences were encountered in the frequency of tumour appearance in rats subjected to long-term (2 years) inhalation of nicotine when compared with control rats [ 48 ]. Despite the lack of carcinogenicity evidence, it has been reported that nicotine promotes tumour cell survival by decreasing apoptosis and increasing proliferation [ 49 ], indicating that it may work as a “tumour enhancer”. In a very recent study, chronic administration of nicotine to mice (1 mg/kg every 3 days for a 60-day period) enhanced brain metastasis by skewing the polarity of M2 microglia, which increases metastatic tumour growth [ 50 ]. Assuming that a conventional cigarette contains 0.172–1.702 mg of nicotine [ 51 ], the daily nicotine dose administered to these animals corresponds to 40–400 cigarettes for a 70 kg-adult, which is a dose of an extremely heavy smoker. We would argue that further studies with chronic administration of low doses of nicotine are required to clearly evaluate its impact on carcinogenicity.

In the aforementioned study exposing human gingival fibroblasts to CS condensate or to nicotine-rich or nicotine-free e-vapour condensates [ 29 ], the detrimental effects were greater in cells exposed to nicotine-rich condensate than to nicotine-free condensate, suggesting that the possible injurious effects of nicotine should be considered when purchasing e-refills . It is also noteworthy that among the 3 most cytotoxic vapours for HUVEC evaluated in the Putzhammer et al . study, 2 were nicotine-free, which suggests that nicotine is not the only hazardous component in e-cigarettes [ 24 ] .

The lethal dose of nicotine for an adult is estimated at 30–60 mg [ 52 ]. Given that nicotine easily diffuses from the dermis to the bloodstream, acute nicotine exposure by e-liquid spilling (5 mL of a 20 mg/mL nicotine-containing refill is equivalent to 100 mg of nicotine) can easily be toxic or even deadly [ 8 ]. Thus, devices with rechargeable refills are another issue of concern with e-cigarettes , especially when e-liquids are not sold in child-safe containers, increasing the risk of spilling, swallowing or breathing.

These data overall indicate that the harmful effects of nicotine should not be underestimated. Despite the established regulations, some inaccuracies in nicotine content labelling remain in different brands of e-liquids . Consequently, stricter regulation and a higher quality control in the e-liquid industry are required.

Effect of humectants and their heating-related products

In this particular aspect, again the composition of the e-liquid varies significantly among different commercial brands [ 4 , 35 ]. The most common and major components of e-liquids are PG or 1,2-propanediol, and glycerol or glycerine (propane-1,2,3-triol). Both types of compounds are used as humectants to prevent the e-liquid from drying out [ 2 , 53 ] and are classified by the Food and Drug Administration (FDA) as “Generally Recognised as Safe” [ 54 ]. In fact, they are widely used as alimentary and pharmaceutical products [ 2 ]. In an analysis of 54 commercially available e-liquids , PG and glycerol were detected in almost all samples at concentrations ranging from 0.4% to 98% (average 57%) and from 0.3% to 95% (average 37%), respectively [ 35 ].

With regards to toxicity, little is known about the effects of humectants when they are heated and chronically inhaled. Studies have indicated that PG can induce respiratory irritation and increase the probability of asthma development [ 55 , 56 ], and both PG and glycerol from e-cigarettes might reach concentrations sufficiently high to potentially cause irritation of the airways [ 57 ]. Indeed, the latter study established that one e-cigarette puff results in a PG exposure of 430–603 mg/m 3 , which is higher than the levels reported to cause airway irritation (average 309 mg/m 3 ) based on a human study [ 55 ]. The same study established that one e-cigarette puff results in a glycerol exposure of 348–495 mg/m 3 [ 57 ], which is close to the levels reported to cause airway irritation in rats (662 mg/m 3 ) [ 58 ].

Airway epithelial injury induced by acute vaping of PG and glycerol aerosols (50:50 vol/vol), with or without nicotine, has been reported in two randomised clinical trials in young tobacco smokers [ 32 ]. In vitro, aerosols from glycerol only-containing refills showed cytotoxicity in A549 and human embryonic stem cells, even at a low battery output voltage [ 59 ]. PG was also found to affect early neurodevelopment in a zebrafish model [ 60 ]. Another important issue is that, under heating conditions PG can produce acetaldehyde or formaldehyde (119.2 or 143.7 ng/puff at 20 W, respectively, on average), while glycerol can also generate acrolein (53.0, 1000.0 or 5.9 ng/puff at 20 W, respectively, on average), all carbonyls with a well-documented toxicity [ 61 ]. Although, assuming 15 puffs per e-cigarette unit, carbonyls produced by PG or glycerol heating would be below the maximum levels found in a conventional cigarette combustion (Table 2 ) [ 51 , 62 ]. Nevertheless, further studies are required to properly test the deleterious effects of all these compounds at physiological doses resembling those to which individuals are chronically exposed.

Although PG and glycerol are the major components of e-liquids other components have been detected. When the aerosols of 4 commercially available e-liquids chosen from a top 10 list of “ Best E-Cigarettes of 2014” , were analysed by gas chromatography-mass spectrometry (GC–MS) after heating, numerous compounds were detected, with nearly half of them not previously identified [ 4 ], thus suggesting that the heating process per se generates new compounds of unknown consequence. Of note, the analysis identified formaldehyde, acetaldehyde and acrolein [ 4 ], 3 carbonyl compounds with known high toxicity [ 63 , 64 , 65 , 66 , 67 ]. While no information was given regarding formaldehyde and acetaldehyde concentrations, the authors calculated that one puff could result in an acrolein exposure of 0.003–0.015 μg/mL [ 4 ]. Assuming 40 mL per puff and 15 puffs per e-cigarette unit (according to several manufacturers) [ 4 ], each e-cigarette unit would generate approximately 1.8–9 μg of acrolein, which is less than the levels of acrolein emitted by a conventional tobacco cigarette (18.3–98.2 μg) [ 51 ]. However, given that e-cigarette units of vaping are not well established, users may puff intermittently throughout the whole day. Thus, assuming 400 to 500 puffs per cartridge, users could be exposed to up to 300 μg of acrolein.

In a similar study, acrolein was found in 11 of 12 aerosols tested, with a similar content range (approximately 0.07–4.19 μg per e-cigarette unit) [ 68 ]. In the same study, both formaldehyde and acetaldehyde were detected in all of the aerosols tested, with contents of 0.2–5.61 μg and 0.11–1.36 μg, respectively, per e-cigarette unit [ 68 ]. It is important to point out that the levels of these toxic products in e-cigarette aerosols are significantly lower than those found in CS: 9 times lower for formaldehyde, 450 times lower for acetaldehyde and 15 times lower for acrolein (Table 2 ) [ 62 , 68 ].

Other compounds that have been detected in aerosols include acetamide, a potential human carcinogen [ 5 ], and some aldehydes [ 69 ], although their levels were minimal. Interestingly, the existence of harmful concentrations of diethylene glycol, a known cytotoxic agent, in e-liquid aerosols is contentious with some studies detecting its presence [ 4 , 68 , 70 , 71 , 72 ], and others finding low subtoxic concentrations [ 73 , 74 ]. Similar observations were reported for the content ethylene glycol. In this regard, either it was detected at concentrations that did not exceed the authorised limit [ 73 ], or it was absent from the aerosols produced [ 4 , 71 , 72 ]. Only one study revealed its presence at high concentration in a very low number of samples [ 5 ]. Nevertheless, its presence above 1 mg/g is not allowed by the FDA [ 73 ]. Figure  1 lists the main compounds detected in aerosols derived from humectant heating and their potential damaging effects. It would seem that future studies should analyse the possible toxic effects of humectants and related products at concentrations similar to those that e-cigarette vapers are exposed to reach conclusive results.

Impact of flavouring compounds

The range of e-liquid flavours available to consumers is extensive and is used to attract both current smokers and new e-cigarette users, which is a growing public health concern [ 6 ]. In fact, over 5 million middle- and high-school students were current users of e-cigarettes in 2019 [ 75 ], and appealing flavours have been identified as the primary reason for e-cigarette consumption in 81% of young users [ 76 ]. Since 2016, the FDA regulates the flavours used in the e-cigarette market and has recently published an enforcement policy on unauthorised flavours, including fruit and mint flavours, which are more appealing to young users [ 77 ]. However, the long-term effects of all flavour chemicals used by this industry (which are more than 15,000) remain unknown and they are not usually included in the product label [ 78 ]. Furthermore, there is no safety guarantee since they may harbour potential toxic or irritating properties [ 5 ].

With regards to the multitude of available flavours, some have demonstrated cytotoxicity [ 59 , 79 ]. Bahl et al. evaluated the toxicity of 36 different e-liquids and 29 different flavours on human embryonic stem cells, mouse neural stem cells and human pulmonary fibroblasts using a metabolic activity assay. In general, those e-liquids that were bubblegum-, butterscotch- and caramel-flavoured did not show any overt cytotoxicity even at the highest dose tested. By contrast, those e-liquids with Freedom Smoke Menthol Arctic and Global Smoke Caramel flavours had marked cytotoxic effects on pulmonary fibroblasts and those with Cinnamon Ceylon flavour were the most cytotoxic in all cell lines [ 79 ]. A further study from the same group [ 80 ] revealed that high cytotoxicity is a recurrent feature of cinnamon-flavoured e-liquids. In this line, results from GC–MS and HPLC analyses indicated that cinnamaldehyde (CAD) and 2-methoxycinnamaldehyde, but not dipropylene glycol or vanillin, were mainly responsible for the high cytotoxicity of cinnamon-flavoured e-liquids [ 80 ]. Other flavouring-related compounds that are associated with respiratory complications [ 81 , 82 , 83 ], such as diacetyl, 2,3-pentanedione or acetoin, were found in 47 out of 51 aerosols of flavoured e-liquids tested [ 84 ] . Allen et al . calculated an average of 239 μg of diacetyl per cartridge [ 84 ]. Assuming again 400 puffs per cartridge and 40 mL per puff, is it is possible to estimate an average of 0.015 ppm of diacetyl per puff, which could compromise normal lung function in the long-term [ 85 ].

The cytotoxic and pro-inflammatory effects of different e-cigarette flavouring chemicals were also tested on two human monocytic cell lines—mono mac 6 (MM6) and U937 [ 86 ]. Among the flavouring chemicals tested, CAD was found to be the most toxic and O-vanillin and pentanedione also showed significant cytotoxicity; by contrast, acetoin, diacetyl, maltol, and coumarin did not show any toxicity at the concentrations assayed (10–1000 µM). Of interest, a higher toxicity was evident when combinations of different flavours or mixed equal proportions of e-liquids from 10 differently flavoured e-liquids were tested, suggesting that vaping a single flavour is less toxic than inhaling mixed flavours [ 86 ]. Also, all the tested flavours produced significant levels of ROS in a cell-free ROS production assay. Finally, diacetyl, pentanedione, O-vanillin, maltol, coumarin, and CAD induced significant IL-8 secretion from MM6 and U937 monocytes [ 86 ]. It should be borne in mind, however, that the concentrations assayed were in the supra-physiological range and it is likely that, once inhaled, these concentrations are not reached in the airway space. Indeed, one of the limitations of the study was that human cells are not exposed to e-liquids per se, but rather to the aerosols where the concentrations are lower [ 86 ]. In this line, the maximum concentration tested (1000 µM) would correspond to approximately 80 to 150 ppm, which is far higher than the levels found in aerosols of some of these compounds [ 84 ]. Moreover, on a day-to-day basis, lungs of e-cigarette users are not constantly exposed to these chemicals for 24 h at these concentrations. Similar limitations were found when five of seven flavourings were found to cause cytotoxicity in human bronchial epithelial cells [ 87 ].

Recently, a commonly commercialized crème brûlée -flavoured aerosol was found to contain high concentrations of benzoic acid (86.9 μg/puff), a well-established respiratory irritant [ 88 ]. When human lung epithelial cells (BEAS-2B and H292) were exposed to this aerosol for 1 h, a marked cytotoxicity was observed in BEAS-2B but not in H292 cells, 24 h later. However, increased ROS production was registered in H292 cells [ 88 ].

Therefore, to fully understand the effects of these compounds, it is relevant the cell cultures selected for performing these assays, as well as the use of in vivo models that mimic the real-life situation of chronic e-cigarette vapers to clarify their impact on human health.

The e-cigarette device

While the bulk of studies related to the impact of e-cigarette use on human health has focused on the e-liquid components and the resulting aerosols produced after heating, a few studies have addressed the material of the electronic device and its potential consequences—specifically, the potential presence of metals such as copper, nickel or silver particles in e-liquids and aerosols originating from the filaments and wires and the atomiser [ 89 , 90 , 91 ].

Other important components in the aerosols include silicate particles from the fiberglass wicks or silicone [ 89 , 90 , 91 ]. Many of these products are known to cause abnormalities in respiratory function and respiratory diseases [ 89 , 90 , 91 ], but more in-depth studies are required. Interestingly, the battery output voltage also seems to have an impact on the cytotoxicity of the aerosol vapours, with e-liquids from a higher battery output voltage showing more toxicity to A549 cells [ 30 ].

A recent study compared the acute effects of e-cigarette vapor (with PG/vegetable glycerine plus tobacco flavouring but without nicotine) generated from stainless‐steel atomizer (SS) heating element or from a nickel‐chromium alloy (NC) [ 92 ]. Some rats received a single e-cigarette exposure for 2 h from a NC heating element (60 or 70 W); other rats received a similar exposure of e-cigarette vapor using a SS heating element for the same period of time (60 or 70 W) and, a final group of animals were exposed for 2 h to air. Neither the air‐exposed rats nor those exposed to e-cigarette vapor using SS heating elements developed respiratory distress. In contrast, 80% of the rats exposed to e-cigarette vapor using NC heating units developed clinical acute respiratory distress when a 70‐W power setting was employed. Thus, suggesting that operating units at higher than recommended settings can cause adverse effects. Nevertheless, there is no doubt that the deleterious effects of battery output voltage are not comparable to those exerted by CS extracts [ 30 ] (Figs.  1 and 2 ).

E-cigarettes as a smoking cessation tool

CS contains a large number of substances—about 7000 different constituents in total, with sizes ranging from atoms to particulate matter, and with many hundreds likely responsible for the harmful effects of this habit [ 93 ]. Given that tobacco is being substituted in great part by e-cigarettes with different chemical compositions, manufacturers claim that e -cigarette will not cause lung diseases such as lung cancer, chronic obstructive pulmonary disease, or cardiovascular disorders often associated with conventional cigarette consumption [ 3 , 94 ]. However, the World Health Organisation suggests that e-cigarettes cannot be considered as a viable method to quit smoking, due to a lack of evidence [ 7 , 95 ]. Indeed, the results of studies addressing the use of e-cigarettes as a smoking cessation tool remain controversial [ 96 , 97 , 98 , 99 , 100 ]. Moreover, both FDA and CDC are actively investigating the incidence of severe respiratory symptoms associated with the use of vaping products [ 77 ]. Because many e-liquids contain nicotine, which is well known for its powerful addictive properties [ 41 ], e-cigarette users can easily switch to conventional cigarette smoking, avoiding smoking cessation. Nevertheless, the possibility of vaping nicotine-free e-cigarettes has led to the branding of these devices as smoking cessation tools [ 2 , 6 , 7 ].

In a recently published randomised trial of 886 subjects who were willing to quit smoking [ 100 ], the abstinence rate was found to be twice as high in the e-cigarette group than in the nicotine-replacement group (18.0% vs. 9.9%) after 1 year. Of note, the abstinence rate found in the nicotine-replacement group was lower than what is usually expected with this therapy. Nevertheless, the incidence of throat and mouth irritation was higher in the e-cigarette group than in the nicotine-replacement group (65.3% vs. 51.2%, respectively). Also, the participant adherence to the treatment after 1-year abstinence was significantly higher in the e-cigarette group (80%) than in nicotine-replacement products group (9%) [ 100 ].

On the other hand, it is estimated that COPD could become the third leading cause of death in 2030 [ 101 ]. Given that COPD is generally associated with smoking habits (approximately 15 to 20% of smokers develop COPD) [ 101 ], smoking cessation is imperative among COPD smokers. Published data revealed a clear reduction of conventional cigarette consumption in COPD smokers that switched to e-cigarettes [ 101 ]. Indeed, a significant reduction in exacerbations was observed and, consequently, the ability to perform physical activities was improved when data was compared with those non-vapers COPD smokers. Nevertheless, a longer follow-up of these COPD patients is required to find out whether they have quitted conventional smoking or even vaping, since the final goal under these circumstances is to quit both habits.

Based on the current literature, it seems that several factors have led to the success of e-cigarette use as a smoking cessation tool. First, some e-cigarette flavours positively affect smoking cessation outcomes among smokers [ 102 ]. Second, e-cigarettes have been described to improve smoking cessation rate only among highly-dependent smokers and not among conventional smokers, suggesting that the individual degree of nicotine dependence plays an important role in this process [ 97 ]. Third, the general belief of their relative harmfulness to consumers' health compared with conventional combustible tobacco [ 103 ]. And finally, the exposure to point-of-sale marketing of e-cigarette has also been identified to affect the smoking cessation success [ 96 ].

Implication of e-cigarette consumption in COVID-19 time

Different reports have pointed out that smokers and vapers are more vulnerable to SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) infections or more prone to adverse outcomes if they suffer COVID-19 [ 104 ]. However, while a systematic review indicated that cigarette smoking is probably associated with enhanced damage from COVID-19, a meta-analysis did not, yet the latter had several limitations due to the small sample sizes [ 105 ].

Interestingly, most of these reports linking COVID-19 harmful effects with smoking or vaping, are based on their capability of increasing the expression of angiotensin-converting enzyme 2 (ACE2) in the lung. It is well known that ACE2 is the gate for SARS-CoV-2 entrance to the airways [ 106 ] and it is mainly expressed in type 2 alveolar epithelial cells and alveolar macrophages [ 107 ]. To date, most of the studies in this field indicate that current smokers have higher expression of ACE2 in the airways (reviewed by [ 108 ]) than healthy non-smokers [ 109 , 110 ]. However, while a recent report indicated that e-cigarette vaping also caused nicotine-dependent ACE2 up-regulation [ 42 ], others have revealed that neither acute inhalation of e-cigarette vapour nor e-cigarette users had increased lung ACE2 expression regardless nicotine presence in the e-liquid [ 43 , 110 ].

In regard to these contentions, current knowledge suggests that increased ACE2 expression is not necessarily linked to enhanced susceptibility to SARS-CoV-2 infection and adverse outcome. Indeed, elderly population express lower levels of ACE2 than young people and SARS-CoV-2/ACE2 interaction further decreases ACE2 expression. In fact, most of the deaths provoked by COVID-19 took place in people over 60 years old of age [ 111 ]. Therefore, it is plausible that the increased susceptibility to disease progression and the subsequent fatal outcome in this population is related to poor angiotensin 1-7 (Ang-1-7) generation, the main peptide generated by ACE2, and probably to their inaccessibility to its anti-inflammatory effects. Furthermore, it seems that all the efforts towards increasing ACE2 expression may result in a better resolution of the pneumonic process associated to this pandemic disease.

Nevertheless, additional complications associated to COVID-19 are increased thrombotic events and cytokine storm. In the lungs, e-cigarette consumption has been correlated to toxicity, oxidative stress, and inflammatory response [ 32 , 112 ]. More recently, a study revealed that while the use of nicotine/flavour-containing e-cigarettes led to significant cytokine dysregulation and potential inflammasome activation, none of these effects were detected in non-flavoured and non-nicotine-containing e-cigarettes [ 43 ]. Therefore, taken together these observations, e-cigarette use may still be a potent risk factor for severe COVID-19 development depending on the flavour and nicotine content.

In summary, it seems that either smoking or nicotine vaping may adversely impact on COVID-19 outcome. However, additional follow up studies are required in COVID-19 pandemic to clarify the effect of e-cigarette use on lung and cardiovascular complications derived from SARS-CoV-2 infection.

Conclusions

The harmful effects of CS and their deleterious consequences are both well recognised and widely investigated. However, and based on the studies carried out so far, it seems that e-cigarette consumption is less toxic than tobacco smoking. This does not necessarily mean, however, that e-cigarettes are free from hazardous effects. Indeed, studies investigating their long-term effects on human health are urgently required. In this regard, the main additional studies needed in this field are summarized in Table 3 .

The composition of e-liquids requires stricter regulation, as they can be easily bought online and many incidences of mislabelling have been detected, which can seriously affect consumers’ health. Beyond their unknown long-term effects on human health, the extended list of appealing flavours available seems to attract new “never-smokers”, which is especially worrying among young users. Additionally, there is still a lack of evidence of e-cigarette consumption as a smoking cessation method. Indeed, e-cigarettes containing nicotine may relieve the craving for smoking, but not the conventional cigarette smoking habit.

Interestingly, there is a strong difference of opinion on e-cigarettes between countries. Whereas countries such as Brazil, Uruguay and India have banned the sale of e-cigarettes , others such as the United Kingdom support this device to quit smoking. The increasing number of adolescent users and reported deaths in the United States prompted the government to ban the sale of flavoured e-cigarettes in 2020. The difference in opinion worldwide may be due to different restrictions imposed. For example, while no more than 20 ng/mL of nicotine is allowed in the EU, e-liquids with 59 mg/dL are currently available in the United States. Nevertheless, despite the national restrictions, users can easily access foreign or even counterfeit products online.

In regard to COVID-19 pandemic, the actual literature suggests that nicotine vaping may display adverse outcomes. Therefore, follow up studies are necessary to clarify the impact of e-cigarette consumption on human health in SARS-CoV-2 infection.

In conclusion, e-cigarettes could be a good alternative to conventional tobacco cigarettes, with less side effects; however, a stricter sale control, a proper regulation of the industry including flavour restriction, as well as further toxicological studies, including their chronic effects, are warranted.

Availability of data and materials

Not applicable.

Abbreviations

Angiotensin-converting enzyme 2

Angiotensin 1-7

Bronchoalveolar lavage fluid

Cinnamaldehyde

US Centers for Disease Control and Prevention

Carbon monoxide

Chronic obstructive pulmonary disease

Coronavirus disease 2019

Cigarette smoke

Electronic nicotine dispensing systems

e-cigarette or vaping product use-associated lung injury

Food and Drug Administration

Gas chromatography with a flame ionisation detector

Gas chromatography-mass spectrometry

Granulocyte–macrophage colony-stimulating factor

High performance liquid chromatography

Human umbilical vein endothelial cells

Interleukin

Interferon γ

Liquid chromatography-mass spectrometry

Monocyte chemoattractant protein-1

Matrix metallopeptidase 9

α7 Nicotinic acetylcholine receptor

Nickel‐chromium alloy

Nitric oxide

Propylene glycol

Regulated on activation, normal T cell expressed and secreted

Reactive oxygen species

Severe acute respiratory syndrome coronavirus 2

Stainless‐steel atomizer

Tetrahydrocannabinol

Tumour necrosis factor-α

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Acknowledgements

The authors gratefully acknowledge Dr. Cruz González, Pulmonologist at University Clinic Hospital of Valencia (Valencia, Spain) for her thoughtful suggestions and support.

This work was supported by the Spanish Ministry of Science and Innovation [Grant Number SAF2017-89714-R]; Carlos III Health Institute [Grant Numbers PIE15/00013, PI18/00209]; Generalitat Valenciana [Grant Number PROMETEO/2019/032, Gent T CDEI-04/20-A and AICO/2019/250], and the European Regional Development Fund.

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Marques, P., Piqueras, L. & Sanz, MJ. An updated overview of e-cigarette impact on human health. Respir Res 22 , 151 (2021). https://doi.org/10.1186/s12931-021-01737-5

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Latest Cochrane Review finds high certainty evidence that nicotine e-cigarettes are more effective than traditional nicotine-replacement therapy (NRT) in helping people quit smoking

A Cochrane review  has found the strongest evidence yet that e-cigarettes, also known as ‘vapes’, help people to quit smoking better than traditional nicotine replacement therapies, such as patches and chewing gums.

New evidence published today in the Cochrane Library finds high certainty evidence that people are more likely to stop smoking for at least six months using nicotine e-cigarettes, or ‘vapes’, than using nicotine replacement therapies, such as patches and gums. Evidence also suggested that nicotine e-cigarettes led to higher quit rates than e-cigarettes without nicotine, or no stop smoking intervention, but less data contributed to these analyses. The updated Cochrane review includes 78 studies in over 22,000 participants – an addition of 22 studies since the last update in 2021.

Smoking is a significant global health problem. According to the World Health Organisation (WHO), in 2020, 22.3% of the global population used tobacco, despite it killing up to half of its users. Stopping smoking reduces the risk of lung cancer, heart attacks and many other diseases. Though most people who smoke want to quit, many find it difficult to do so permanently. Nicotine patches and gum are safe, effective and widely used methods to help individuals quit.

E-cigarettes heat liquids with nicotine and flavourings, allowing users to ‘vape’ nicotine instead of smoking. Data from the review showed that i f six in 100 people quit by using nicotine replacement therapy, eight to twelve would quit by using electronic cigarettes containing nicotine. This means an additional two to six people in 100 could potentially quit smoking with nicotine containing electronic cigarettes.

Dr Jamie Hartmann-Boyce, Associate Professor at the University of Oxford, Editor of the Cochrane Tobacco Addiction Group, and an author of the new publication, said:

“Electronic cigarettes have generated a lot of misunderstanding in both the public health community and the popular press since their introduction over a decade ago. These misunderstandings discourage some people from using e-cigarettes as a stop smoking tool. Fortunately, more and more evidence is emerging and provides further clarity. With support from Cancer Research UK, we search for new evidence every month as part of a living systematic review. We identify and combine the strongest evidence from the most reliable scientific studies currently available. For the first time, this has given us high-certainty evidence that e-cigarettes are even more effective at helping people to quit smoking than traditional nicotine replacement therapies, like patches or gums.”

In studies comparing nicotine e-cigarettes to nicotine replacement treatment, significant side effects were rare. In the short-to-medium term (up to two years), nicotine e-cigarettes most typically caused throat or mouth irritation, headache, cough, and feeling nauseous. However, these effects appeared to diminish over time.

Dr Nicola Lindson, University Research Lecturer at the University of Oxford, Cochrane Tobacco Addiction Group’s Managing Editor, and author of the publication said:

“ E-cigarettes do not burn tobacco; and as such they do not expose users to the same complex mix of chemicals that cause diseases in people smoking conventional cigarettes. E-cigarettes are not risk free, and shouldn’t be used by people who don’t smoke or aren’t at risk of smoking. However, evidence shows that nicotine e-cigarettes carry only a small fraction of the risk of smoking. In our review, we did not find evidence of substantial harms caused by nicotine containing electronic cigarettes when used to quit smoking. However, due to the small number of studies and lack of data on long-term nicotine-containing electronic cigarette usage – usage over more than two years – questions remain about long-term effects.”

The researchers conclude that more evidence, particularly about the effects of newer e-cigarettes with better nicotine delivery than earlier ones, is needed to assist more people quit smoking. Longer-term data is also needed.

Michelle Mitchell, chief executive at Cancer Research UK, said:

“We welcome this report which adds to a growing body of evidence showing that e-cigarettes are an effective smoking cessation tool. We strongly discourage those who have never smoked from using e-cigarettes, especially young people. This is because they are a relatively new product and we don’t yet know the long term health effects. While the long term effects of vaping are still unknown, the harmful effects of smoking are indisputable – smoking causes around 55,000 cancer deaths in the UK every year. Cancer Research UK supports balanced evidence-based regulation on e-cigarettes from UK governments which maximises their potential to help people stop smoking, whilst minimising the risk of uptake among others.”

• Read the full Cochrane review and plain language summary 
• Learn more about Cochrane Tobacco Addition Group
• Science Media Centre: Expert reaction to cochrane review on electronic cigarettes for smoking cessation

 Hartmann-Boyce J, Lindson N, Butler AR, McRobbie H, Bullen C, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Fanshawe TR, Hajek P. Electronic cigarettes for smoking cessation. Cochrane Database of Systematic Reviews 2022, Issue 11. Art. No.: CD010216. DOI: 10.1002/14651858.CD010216.pub7

This work was supported by Cancer Research UK [A ref. A29845]

To speak to a team member about this project please contact Dr. Hartmann-Boyce, [email protected] or Dr. Lindson, [email protected] .

Latest Cochrane Review finds high certainty evidence that nicotine e-cigarettes are more effective than traditional nicotine-replacement therapy (NRT) in helping people quit smoking

17 November 2022

Research led by the University of Oxford, and funded by Cancer Research UK, has found the strongest evidence yet that e-cigarettes, also known as ‘vapes’, help people to quit smoking better than traditional nicotine replacement therapies, such as patches and chewing gums.

New evidence published today in the Cochrane Library finds high certainty evidence that people are more likely to stop smoking for at least six months using nicotine e-cigarettes, or ‘vapes’, than using nicotine replacement therapies, such as patches and gums. Evidence also suggested that nicotine e-cigarettes led to higher quit rates than e-cigarettes without nicotine, or no stop smoking intervention, but less data contributed to these analyses. The updated Cochrane review includes 78 studies in over 22,000 participants – an addition of 22 studies since the last update in 2021.

Smoking is a significant global health problem. According to the World Health Organisation (WHO), in 2020, 22.3% of the global population used tobacco, despite it killing up to half of its users. Stopping smoking reduces the risk of lung cancer, heart attacks and many other diseases. Though most people who smoke want to quit, many find it difficult to do so permanently. Nicotine patches and gum are safe, effective and widely used methods to help individuals quit.

E-cigarettes heat liquids with nicotine and flavourings, allowing users to ‘vape’ nicotine instead of smoking. Data from the review showed that if six in 100 people quit by using nicotine replacement therapy, eight to twelve would quit by using electronic cigarettes containing nicotine. This means an additional two to six people in 100 could potentially quit smoking with nicotine containing electronic cigarettes.

Dr Jamie Hartmann-Boyce, Associate Professor at the University of Oxford, Editor of the Cochrane Tobacco Addiction Group, and an author of the new publication, said: “Electronic cigarettes have generated a lot of misunderstanding in both the public health community and the popular press since their introduction over a decade ago. These misunderstandings discourage some people from using e-cigarettes as a stop smoking tool. Fortunately, more and more evidence is emerging and provides further clarity. With support from Cancer Research UK, we search for new evidence every month as part of a living systematic review. We identify and combine the strongest evidence from the most reliable scientific studies currently available.

For the first time, this has given us high-certainty evidence that e-cigarettes are even more effective at helping people to quit smoking than traditional nicotine replacement therapies, like patches or gums.”

In studies comparing nicotine e-cigarettes to nicotine replacement treatment, significant side effects were rare. In the short-to-medium term (up to two years), nicotine e-cigarettes most typically caused throat or mouth irritation, headache, cough, and feeling nauseous. However, these effects appeared to diminish over time.

Dr Nicola Lindson, University Research Lecturer at the University of Oxford, Cochrane Tobacco Addiction Group’s Managing Editor, and author of the publication said: “E-cigarettes do not burn tobacco; and as such they do not expose users to the same complex mix of chemicals that cause diseases in people smoking conventional cigarettes. E-cigarettes are not risk free, and shouldn’t be used by people who don’t smoke or aren’t at risk of smoking. However, evidence shows that nicotine e-cigarettes carry only a small fraction of the risk of smoking. In our review, we did not find evidence of substantial harms caused by nicotine containing electronic cigarettes when used to quit smoking. However, due to the small number of studies and lack of data on long-term nicotine-containing electronic cigarette usage – usage over more than two years – questions remain about long-term effects.”

The researchers conclude that more evidence, particularly about the effects of newer e-cigarettes with better nicotine delivery than earlier ones, is needed to assist more people quit smoking. Longer-term data is also needed.

Michelle Mitchell, chief executive at Cancer Research UK, said: “We welcome this report which adds to a growing body of evidence showing that e-cigarettes are an effective smoking cessation tool. We strongly discourage those who have never smoked from using e-cigarettes, especially young people. This is because they are a relatively new product and we don’t yet know the long term health effects.“

“While the long term effects of vaping are still unknown, the harmful effects of smoking are indisputable – smoking causes around 55,000 cancer deaths in the UK every year. Cancer Research UK supports balanced evidence-based regulation on e-cigarettes from UK governments which maximises their potential to help people stop smoking, whilst minimising the risk of uptake among others.”

This work was supported by Cancer Research UK [A ref. A29845]

Notes to Editors:

https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010216.pub7/full

doi: 10.1002/14651858.CD010216.pub7 Lead authors: Associate Professor at the Nuffield Department of Primary Care Health Sciences, University of Oxford and Editor of the Cochrane Tobacco Addiction Group, Dr Jamie Hartmann-Boyce and Senior Researcher at the Nuffield Department of Primary Care Health Sciences, University of Oxford and Managing Editor of the Cochrane Tobacco Addiction Group, Dr Nicola Lindson.

To speak to a team member about this project please contact Dr. Hartmann-Boyce, [email protected] or Dr. Lindson, [email protected] .

About Cochrane Cochrane is a global independent network of researchers, professionals, patients, carers, and people interested in health. Cochrane produces reviews which study all the best available evidence generated through research and make it easier to inform decisions about health. These are called systematic reviews. Cochrane is a not-for profit organization with collaborators from more than 130 countries working together to produce credible, accessible health information that is free from commercial sponsorship and other conflicts of interest. Our work is recognized as representing an international gold standard for high-quality, trusted information. Find out more at cochrane.org

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Study Links E-Cigarette Use with Higher Risk of Heart Failure

Large study adds to growing body of evidence that vaping may harm the heart.

Apr 02, 2024

Contact: Nicole Napoli , [email protected], 202-669-1465

WASHINGTON (Apr 02, 2024) -

People who use e-cigarettes are significantly more likely to develop heart failure compared with those who have never used them, according to one of the largest prospective studies to date investigating possible links between vaping and heart failure. The findings are being presented at the American College of Cardiology’s Annual Scientific Session.

Heart failure is a condition affecting more than 6 million U.S. adults in which the heart becomes too stiff or too weak to pump blood as effectively as it should. It can often lead to debilitating symptoms and frequent hospitalizations as people age. Electronic nicotine products, which include e-cigarettes, vape pens, hookah pens, personal vaporizers and mods, e-cigars, e-pipes and e-hookahs, deliver nicotine in aerosol form without combustion. Since they were first introduced in the U.S. in the late 2000s, electronic nicotine products have often been portrayed as a safer alternative to smoking, but a growing body of research has led to increased concern about potential negative health effects.

“More and more studies are linking e-cigarettes to harmful effects and finding that it might not be as safe as previously thought,” said Yakubu Bene-Alhasan, MD, a resident physician at MedStar Health in Baltimore and the study’s lead author. “The difference we saw was substantial. It’s worth considering the consequences to your health, especially with regard to heart health.”

For the study, researchers used data from surveys and electronic health records in All of Us, a large national study of U.S. adults run by the National Institutes of Health, to analyze associations between e-cigarette use and new diagnoses of heart failure in 175,667 study participants (an average age of 52 years and 60.5% female). Of this sample, 3,242 participants developed heart failure within a median follow-up time of 45 months.

The results showed that people who used e-cigarettes at any point were 19% more likely to develop heart failure compared with people who had never used e-cigarettes. In calculating this difference, researchers accounted for a variety of demographic and socioeconomic factors, other heart disease risk factors and participants’ past and current use of other substances, including alcohol and tobacco products. The researchers also found no evidence that participants’ age, sex or smoking status modified the relationship between e-cigarettes and heart failure.

Breaking the data down by type of heart failure, the increased risk associated with e-cigarette use was statistically significant for heart failure with preserved ejection fraction (HFpEF)—in which the heart muscle becomes stiff and does not properly fill with blood between contractions. However, this association was not significant for heart failure with reduced ejection fraction (HFrEF)—in which the heart muscle becomes weak and the left ventricle does not squeeze as hard as it should during contractions. Rates of HFpEF have risen in recent decades, which has led to an increased focus on determining risk factors and improving treatment options for this type of heart failure.

The findings align with previous studies conducted in animals, which signaled e-cigarette use can affect the heart in ways that are relevant to the heart changes involved in heart failure. Other studies in humans have also shown links between e-cigarette use and some risk factors associated with developing heart failure. However, previous studies attempting to assess the direct connection between e-cigarette use and heart failure have been inconclusive, which Bene-Alhasan said is due to the inherent limitations of the cross-sectional study designs, smaller sample sizes and the smaller number of heart failure events seen in previous research.

Researchers said the new study findings point to a need for additional investigations of the potential impacts of vaping on heart health, especially considering the prevalence of e-cigarette use among younger people. Surveys indicate that about 5% to 10% of U.S. teens and adults use e-cigarettes. In 2018, the U.S. Surgeon General called youth e-cigarette use an epidemic and warned about the health risks associated with nicotine addiction.

“I think this research is long overdue, especially considering how much e-cigarettes have gained traction,” Bene-Alhasan said. “We don’t want to wait too long to find out eventually that it might be harmful, and by that time a lot of harm might already have been done. With more research, we will get to uncover a lot more about the potential health consequences and improve the information out to the public.”

Bene-Alhasan also said e-cigarettes are not recommended as a tool to quit smoking, since many people may continue vaping long after they quit smoking. The U.S. Centers for Disease Control and Prevention recommends a combination of counseling and medications as the best strategy for quitting smoking.

Researchers said that the study’s prospective observational design allows them to infer, but not conclusively determine, a causal relationship between e-cigarette use and heart failure. However, with its large sample size and detailed data on substance use and health information, Bene-Alhasan said the study is one of the most comprehensive studies to assess this relationship to date.

For more information about the health effects of e-cigarettes, visit CardioSmart.org/StopSmoking .

Bene-Alhasan will present the study, “Electronic Nicotine Product Use Is Associated with Incident Heart Failure - The All of Us Research Program,” on Sunday, April 7, 2024, at 3:15 p.m. ET / 19:15 UTC in Hall B4-5.

ACC.24  will take place April 6-8, 2024, in Atlanta, bringing together cardiologists and cardiovascular specialists from around the world to share the newest discoveries in treatment and prevention. Follow  @ACCinTouch ,  @ACCMediaCenter  and  #ACC24  for the latest news from the meeting.

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• Systematic Review
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• Published: 10 September 2024

Association of electronic cigarette use and suicidal behaviors: a systematic review and meta-analysis

• Abdelaziz A. Awad 1   na1 ,
• Ramaiah Itumalla 2   na1 ,
• Abhay M. Gaidhane 3 ,
• Mahalaqua Nazli Khatib 4 ,
• Suhas Ballal 5 ,
• Pooja Bansal 6 ,
• Manish Srivastava 7 ,
• Isha Arora 8 ,
• MRavi Kumar 9 ,
• Aashna Sinha 10 ,
• Kumud Pant 11 , 12 ,
• Hashem Abu Serhan 13 &
• Muhammed Shabil 14 , 15  

BMC Psychiatry volume  24 , Article number:  608 ( 2024 ) Cite this article

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The proliferation of electronic cigarettes (e-cigarettes) has presented new challenges in public health, particularly among adolescents and young adults. While marketed as safer than tobacco and as cessation aids, e-cigarettes have raised concerns about their long-term health and psychosocial impacts, including potential links to increased suicidal behaviors. This study aims to evaluate the relationship between e-cigarette use and suicidal behaviors by conducting a systematic review of the current literature.

We searched PubMed, Web of Science, and EMBASE for studies up to March 10, 2024, examining the relationship between e-cigarette use and suicidal behaviors. Eligible studies included cross-sectional, longitudinal, retrospective, prospective, and case–control designs. Meta-analysis was performed to calculate pooled odds ratios (ORs). Newcastle Ottawa scale was used to assess the quality of studies. R software (V 4.3) was used to perform the meta-analysis.

Our analysis included fourteen studies, predominantly from the US and Korea, with participants ranging from 1,151 to 255,887. The meta-analysis identified a significant association between e-cigarette use and an increased risk of suicidal ideation (OR = 1.489, 95% CI: 1.357 to 1.621), suicide attempts (OR = 2.497, 95% CI: 1.999 to 3.996), and suicidal planning (OR = 2.310, 95% CI: 1.810 to 2.810). Heterogeneity was noted among the studies.

E-cigarette use is significantly associated with the risk of suicidal behaviors, particularly among adolescents. The findings underscore the necessity for caution in endorsing e-cigarettes as a safer smoking alternative and call for more extensive research to understand the underlying mechanisms. Public health strategies should be developed to address and mitigate the risks of suicidal behaviors among e-cigarette users.

Peer Review reports

Introduction

The advent of electronic cigarettes (e-cigarettes) has ushered in a new era in the landscape of tobacco consumption, offering a technological alternative to traditional smoking methods [ 1 , 2 , 3 , 4 ]. Marketed as a safer option and a potential tool for smoking cessation, e-cigarettes have rapidly gained popularity among various demographics, notably among teens and young adults [ 5 ]. However, this rise in e-cigarette use has been paralleled by growing concerns among health professionals and researchers regarding their long-term health implications and psychosocial outcomes [ 6 , 7 , 8 , 9 , 10 , 11 ].

The use of e-cigarettes, especially among adolescents and young adults, poses significant health concerns [ 12 ]. While e-cigarettes are often marketed as a safer alternative to traditional tobacco products, they are not without risks [ 11 , 13 ]. Studies have shown that e-cigarette use can lead to increased exposure to harmful chemicals such as nicotine, which can adversely affect brain development in youths and lead to addiction. Additionally, there is evidence linking e-cigarette use with respiratory issues and the potential for cardiovascular harm [ 14 ]. The prevalence of e-cigarette use among adolescents and young adults has been rising, driven by factors such as appealing flavors, targeted marketing, and the perception of reduced harm compared to smoking [ 15 ]. This trend is alarming, as early exposure to nicotine can establish long-lasting addictive behaviors, potentially leading to the use of other tobacco products and sustaining a cycle of dependence that can be difficult to break.

Among the most alarming potential consequences is the impact of e-cigarette use on mental health, a subject that has recently begun to garner attention within the scientific community [ 16 , 17 ]. Suicidal behaviors, encompassing suicidal ideation, planning, attempts, and completed suicide, represent a significant public health issue worldwide [ 18 ]. The World Health Organization (WHO) reports that nearly 700,000 people pass away from suicide each year, positioning it as the second most common cause of death among individuals aged 15 to 29 years. [ 19 ]. The etiology of suicidal behaviors is multifaceted, with a complex interplay of psychological, genetic, and environmental and social factors [ 20 , 21 ]. Recently, substance use, including the consumption of nicotine through smoking, has been identified as a risk factor for suicidal behaviors [ 22 , 23 , 24 ]. Nicotine's neurobiological effects, which can influence mood and cognitive function, alongside the psychosocial aspects of substance use, may contribute to this association [ 23 , 25 ].

The emergence of e-cigarettes, which deliver nicotine without the combustion of tobacco, was initially met with optimism for their potential to reduce the harm associated with traditional cigarette smoking [ 26 , 27 ]. Nonetheless, the impact of e-cigarettes on mental health, and specifically their association with suicidal behaviors, remains underexplored and poorly understood. Preliminary studies have suggested a potential association between e-cigarette use and increased risk of suicidal behaviors [ 28 , 29 , 30 , 31 ]. Some studies have found that e-cigarette use is associated with increased suicidal ideation, suicide planning, and suicide attempts among adolescents. For instance, a study in South Korea found that among male participants, rates of suicidal ideation, suicide planning, and suicide attempts were higher among those who initially used e-cigarettes compared to those who initially used conventional cigarettes or never smoked [ 32 ]. Similarly, a scoping review of vaping and mental health found that e-cigarette use was associated with depression, suicidal ideation, and suicide attempts among adolescents [ 33 ]. Additionally, a study in the US found that the use of e-cigarettes was associated with 23% increased odds of seriously considering attempting suicide in the prior year among more than 25,000 adolescents participating in the US Youth Risk Behavior Survey [ 34 ]. These findings suggest that e-cigarette use may be a significant risk factor for suicide behaviors globally.

A systematic review has yet to be conducted to assess this issue. This systematic review and meta-analysis aimed to address this gap by evaluating the existing body of research on the association between e-cigarette use and suicidal behaviors. By aggregating data from diverse studies, this work seeks to provide a more robust understanding of the relationship. Through this analysis, we endeavor to contribute valuable insights into the potential psychosocial risks associated with e-cigarette use, offering a foundation for future research and informing policy-makers and healthcare providers in their efforts to mitigate the adverse outcomes related to e-cigarette consumption.

This systematic review and meta-analysis adhered to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) to ensure transparency and completeness in reporting [ 35 ] (Table S1). The aim was to systematically review and synthesize existing literature on the association between e-cigarette use and suicidal behaviors, including suicidal ideation, planning, attempts, and completion. This systematic review has been registered prospectively in PROSPERO.

Search strategy

A search strategy was developed to identify studies that investigated the association between e-cigarette use and suicidal behaviors. Electronic databases, including PubMed, Web of Science, and EMBASE, were searched from their inception to March 10, 2024. The search strategy combined terms related to e-cigarettes (e.g., "electronic cigarettes," "e-cigarettes," "vaping") with terms related to suicidal behaviors (e.g., "suicide," "suicidal" AND “self-harm"). Both MeSH terms (where applicable) and free text terms were used. The search strategy is displayed in Table S2.

Eligibility criteria

For inclusion, we considered studies involving participants from the general population without any restrictions, thus allowing for a broad and inclusive analysis. The exposure of interest was clearly defined as the use of e-cigarettes, vaping products, or Electronic Nicotine Delivery Systems (ENDS), excluding studies that focused solely on traditional tobacco smoking due to its well-documented effects and distinct mechanisms compared to e-cigarettes. Regarding outcomes, we aimed to include studies that investigated suicidal ideation, suicidal planning, and suicidal attempts, explicitly excluding research that focused on non-suicidal self-harms to maintain a clear focus on suicidal behaviors directly. In terms of study design, our criteria included a wide range of observational studies, encompassing cross-sectional, longitudinal, retrospective, prospective, and case–control studies. We excluded qualitative studies, policy analyses, opinion pieces, case studies, case reports, reviews, and animal studies from our analysis, as these did not offer the empirical evidence necessary to address our research question directly (Table S3).

Study selection

Titles and abstracts were screened for eligibility independently by two reviewers, utilizing Nested-Knowledge web software for the process. Subsequently, full texts of studies that appeared potentially suitable were retrieved and assessed independently for inclusion. Any discrepancies were settled through discussion or by consulting a third reviewer.

Data extraction

Data extraction was conducted independently by two reviewers utilizing a uniform data extraction template. The information extracted encompassed characteristics of the study (such as author, publication year, country, design of the study, and size of the sample), demographics of the participants, and outcomes pertaining to suicidal behaviors. Discrepancies encountered during the data extraction process were addressed through discussions or by seeking the opinion of a third reviewer.

Quality assessment

The assessment of the quality of the included studies was carried out using the Newcastle–Ottawa Scale. This scale assesses the selection criteria of the study groups, the comparability between these groups, and the determination of the exposure or outcome of interest.

Statistical analysis

The meta-analysis employed a random-effects model (REM) to accommodate expected variability among the studies, offering a more standardized estimate of the overall effect. This approach is designed to manage the inherent differences found across studies. The relationship between the use of e-cigarettes and suicidal behaviors was measured using odds ratios (ORs) accompanied by 95% confidence intervals (CIs). The degree of heterogeneity between the studies was evaluated using the I 2 statistic [ 36 ]. Additionally, a 95% prediction interval was utilized to provide deeper insight into the degree of heterogeneity. To examine publication bias, funnel plots and Egger's test were applied. The analysis was conducted using the ‘Meta’ and ‘Metafor’ packages within the R statistical software (Version 4.3) [ 37 ].

Literature search

The initial search yielded 288 records, which were reduced to 180 after the removal of 108 duplicate entries. Each of these records was screened based on our predefined criteria, identifying 22 potentially relevant reports for full retrieval. Upon closer examination, eight of these were excluded due to their lack of reporting on the outcomes of interest, specifically related to suicidal behaviors in the context of e-cigarette use. The screening process culminated in selecting 14 suitable studies [ 28 , 29 , 30 , 31 , 32 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] for inclusion in our systematic review and meta-analysis (Fig. 1 ).

PRISMA flow diagram showing article screening and study selection process

Characteristics of included studies

The included studies in this systematic review primarily focus on the United States (US) and Korea, with a single study from Canada (Table 1 ). These studies employed a cross-sectional design to investigate the association between e-cigarette use and suicidal behaviors across diverse demographic groups, including active-duty service members, adolescents, bisexual high school students, asthmatic adolescents, the general population, and middle and high school students. The sample sizes vary significantly, ranging from 1,151 to 255,887 participants, with most studies reporting a balanced gender distribution where applicable.

Ahmed's 2023 study [ 38 ] on active-duty service members from the US military branches reports an OR of 2.00 for suicide ideation and 2.64 for suicide attempts. Baiden's 2022 [ 28 ] research on US high school students shows ORs ranging from 1.55 for suicide ideation to 1.75 for suicide attempts, with explicit data on planning as well. Chadi's 2019 study [ 29 ], Dunn's 2023 study [ 39 ], and Erhabor's 2023 study [ 40 ], all based in the US, focus on adolescents and specific groups such as bisexual students, offering varying ORs for suicide ideation and plans. Huh's 2021 study [ 30 ] stands out with its Korean adolescent population, presenting higher ORs, especially for suicide attempts, peaking at 4.26. Kim's series of studies from 2020 and 2021 in Korea explore different populations, including asthmatic adolescents and the general population, with ORs for suicide ideation and attempts indicating a considerable risk associated with e-cigarette use. Lee's 2019 [ 44 ] study from Korea provides a detailed breakdown by gender, revealing a stark contrast in ORs for suicide attempts between males and females. Pham's 2020 study [ 45 ] is the only Canadian entry offering gender-specific ORs for suicide ideation. Finally, Welty's 2023 study [ 46 ] focuses on US high school students, providing data exclusively for suicide attempts with an OR of 3.0. The quality assessment of studies is given in Table S4.

Suicide ideation

The meta-analysis for suicidal ideation associated with electronic cigarette use incorporated data from various studies, yielding pooled ORs. The pooled OR, derived using a REM, stands at 1.489 (95% CI: 1.357 to 1.621), indicating a significant relationship between e-cigarette use and an increased risk of suicidal ideation. This pooled estimate, while accounting for the variability among individual study results, underscores a nearly 50% increase in the odds of suicidal ideation among e-cigarette users versus non-users. The prediction interval (1.143 to 1.835) suggests that the true effect in an individual study is expected to lie within this range 95% of the time. The heterogeneity of the analysis, as shown by an I 2 value of 46%, suggests moderate variability (Fig.  2 ). In adolescents or children who use e-cigarettes, the pooled OR for suicide ideation was found to be 1.46 (95% CI: 1.332 to 1.589), with a heterogeneity of I 2  = 56% (Figure S1).

Forest plot illustrating the meta-analysis of association of e-cigarettes and suicidal ideation

Suicidal plan

In the meta-analysis examining the relationship between e-cigarette use and suicidal planning, a pooled analysis of the selected studies was conducted. The OR for suicidal planning is calculated at 2.310 (95% CI: 1.810 to 2.810), suggesting a statistically significant relationship between e-cigarette use and a heightened risk of suicidal planning. The heterogeneity among the studies, indicated by an I 2 value of 71%, is considered substantial. The prediction interval, from 0.787 to 3.832, also indicates the expected range of true effects in similar future studies, acknowledging the variability observed in the current analysis. This wide range suggests that while the overall trend points towards increased risk, individual studies may report varying degrees of association (Fig.  3 ). In adolescents or children who use e-cigarettes, the pooled OR for suicide planning was found to be 2.226 (95% CI: 1.739 to 2.712), with a heterogeneity of I 2  = 73% (Figure S2).

Forest plot illustrating the meta-analysis of association of e-cigarettes and suicidal plan

Suicidal attempt

In the meta-analysis regarding the link between e-cigarette use and suicide attempts, the selected studies encompassed a variety of populations and settings, providing a broad perspective on the issue. The ORs from individual studies point toward a relationship between e-cigarette use and an elevated risk of suicide attempts. The aggregated results yield a pooled OR of 2.497 (95% CI: 1.999 to 3.996), which indicates a significant risk of suicide attempts among e-cigarette users. The heterogeneity of the analysis is high, with an I 2 value of 67%. Despite this variability, the prediction interval, ranging from 0.992 to 4.002, suggests that future studies are likely to find a true effect within this range, supporting the presence of a linkage between e-cigarette use and suicide attempts (Fig.  4 ). In adolescents or children who use e-cigarettes, the pooled OR for suicide attempts was found to be 2.462 (95% CI: 1.944 to 2.980), with a heterogeneity of I 2  = 72% (Figure S3).

Forest plot illustrating the meta-analysis of association of e-cigarettes and suicide attempt

Sensitivity analysis

We performed a sensitivity analysis using the leave-one-out approach, and no significant variation in the results was noted for any of the outcomes. All outcomes remain significantly associated with e-cigarette use in the sensitivity analysis (Figures S4–S6).

Publication bias

The assessment for publication bias in our meta-analysis was conducted through visual inspection of funnel plots and the Egger test for suicidal attempts and ideation, as presented in Fig.  5 . Due to the limited number of studies available, we did not statistically evaluate publication bias for suicidal planning. Visual inspection of the funnel plots revealed asymmetry. Furthermore, the Egger test results ( p  = 0.0008 for suicidal ideation, p  = 0.0143 for suicidal attempts) also indicated the presence of publication bias.

Funnel plot showing publication bias assessment

We further performed trim and fill analyses (Figures S7 and S8). The OR for suicide ideation was found to be 1.3865 (95% CI: 1.2459 to 1.5271), and for suicide attempts, it was 2.0404 (95% CI: 1.3660 to 2.7148). These results indicate that, even without the effects of small studies, the association between e-cigarette use and suicidal behaviors remains significant.

The findings from our study provide strong evidence of a significant association between e-cigarette use and an increased risk of suicidal behaviors, including ideation, plan and attempts. This is particularly notable given the rising prevalence of e-cigarette use, especially among adolescents and young adults. Our analysis indicates a nearly 50% increase in the odds of suicidal ideation and more than a doubling in the risk of suicide attempts among e-cigarette users. These associations persisted in general population and adolescents, suggesting a potential universal relationship between e-cigarette use and suicidal behaviors rather than one confined to specific contexts.

The potential mechanisms underlying the relationship between e-cigarette use and suicidal behaviors could be multifactorial. Nicotine is a primary component in most e-cigarettes and is known to influence neurotransmitter activity within the brain, potentially altering mood [ 23 ]. Additionally, nicotine dependence may contribute to psychological stress, a well-documented risk factor for suicidal behaviors. This is particularly concerning as nicotine can impact neurobiological changes during critical periods of brain development among adolescents, underscoring the potential for e-cigarettes to affect mental health in this vulnerable group.

The findings of this study might also be shaped by cultural and social factors that can influence both e-cigarette usage and suicidal behaviors. Different cultural attitudes towards mental health, smoking, and the acceptance of e-cigarettes can significantly affect how individuals perceive and engage with these products [ 47 , 48 ]. Social norms, the prevalence of e-cigarette advertising, and the level of awareness about mental health issues vary widely across different regions and cultures, potentially impacting the prevalence of e-cigarette use and its association with suicidal behaviors [ 49 ]. Therefore, cultural context and social dynamics variations are essential considerations when interpreting the results and could explain differences in the observed outcomes across different populations.

Prior systematic reviews have explored the impact of e-cigarettes on mental health. For example, Becker et al.'s study highlighted increased mental health issues in young e-cigarette users relative to non-users, particularly in adolescents [ 17 ]. Beyond mental health, e-cigarettes have been associated to a range of adverse health outcomes, such as addiction, poisoning, inhalation toxicity, cardiovascular alterations, and diminished lung function as indicated by an umbrella review [ 50 ]. Furthermore, the use of e-cigarettes among individuals who have never smoked is linked with an increased likelihood of tobacco smoking initiation, potentially leading to regular smoking habits [ 51 ]. A previous scoping review found that suicide attempts were notably more frequent in individuals who used e-cigarettes compared to those who did not [ 33 ]. The use of e-cigarettes was linked with depression, suicidal ideation, and suicide attempts [ 33 ]. There was a significant increase in suicide attempts among e-cigarette users relative to non-users. These results are comparable to ours.

E-cigarettes, frequently advertised as safer substitutes for conventional cigarettes and as assistance for quitting smoking, are at the centre of ongoing debates. The current evidence on their efficacy and safety is mixed, with no long-term conclusive data to confirm their effectiveness in helping individuals quit tobacco smoking. While some randomized controlled trials (RCTs) have indicated that e-cigarette might assist some smokers in reducing or quitting tobacco use, numerous observational studies have not found significant benefits in quitting tobacco through e-cigarette [ 52 , 53 ]. Additionally, e-cigarette have associated health risks, such as the potential for nicotine addiction among non-smokers, particularly youth [ 54 , 55 ].

The regulation of ENDS poses a complex challenge, especially in limiting youth access. The legislative approach to ENDS varies globally, with some countries implementing stringent regulations or outright bans and others having little to no controls. The WHO reports that while 34 countries have banned e-cigarette sales, 88 countries do not restrict age for purchasing these products [ 56 ]. Preventing ENDS from becoming a gateway to tobacco smoking for young people necessitates re-evaluation of their accessibility to this demographic. Effective regulation requires ongoing surveillance of ENDS use among both adults and youth, public health initiatives to inform about potential benefits for smokers and risks for non-smokers and young people, and policies mandating the reporting of adverse events.

Our study has some limitations. The cross-sectional nature of the majority of the included studies limits the ability to establish causality. There is also significant variability in the measurement of e-cigarette use and suicidal behaviors across the studies, which could contribute to the heterogeneity of our findings. The lack of longitudinal studies prevents a more thorough examination of the temporal relationship between these variables. Additionally, the majority of the research is concentrated in the USA and Korea, which may limit the generalizability of our findings to other regions. The presence of publication bias is also a concern, as studies with non-significant findings may be underrepresented in the literature. Our analysis might not have fully considered all relevant demographic variables that could influence the relationship between e-cigarette use and suicidal behaviors, such as socioeconomic status or underlying mental health conditions. Finally, the rapid evolution of e-cigarette products and the variability in their nicotine content might not have been fully accounted for, which could affect the applicability of our results to all e-cigarette users.

Our analysis provided evidence of a relationship between e-cigarette use and an increased risk of suicidal ideation, plan, and attempts. The findings highlight the need for caution among health professionals and policy-makers in promoting e-cigarettes as safe alternatives to smoking. They also point to the necessity for further, high-quality research to explore the interventions aimed at reducing suicidal behaviors among e-cigarette users. Given the significant public health implications, a coordinated effort to address the mental health risks associated with e-cigarette use is warranted.

Availability of data and materials

The data is with the authors and available on request to the corresponding author (HAS), Email: [email protected].

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Acknowledgements

The authors acknowledge the Nested-Knowledge, MN, USA for providing the access to the software.

Name of internal review board

Not applicable.

Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). This study received no funding.

Author information

Abdelaziz A. Awad and Ramaiah Itumalla contributed as first authors.

Authors and Affiliations

Faculty of Medicine, Al-Azhar University, Cairo, 11651, Egypt

Abdelaziz A. Awad

School of Management, The Apollo University, Chittoor, Andhra Pradesh, 517127, India

Ramaiah Itumalla

School of Epidemiology and Public Health, Jawaharlal Nehru Medical College, and Global Health Academy, Datta Meghe Institute of Higher Education, Wardha, India

Abhay M. Gaidhane

Division of Evidence Synthesis, Global Consortium of Public Health and Research, Datta Meghe Institute of Higher Education, Wardha, India

Mahalaqua Nazli Khatib

Department of Chemistry and Biochemistry, School of Sciences, JAIN (Deemed to Be University), Bangalore, Karnataka, India

Suhas Ballal

Department of Allied Healthcare and Sciences, Vivekananda Global University, Jaipur, Rajasthan, 303012, India

Pooja Bansal

Department of Cardiology, NIMS University, Jaipur, India

Manish Srivastava

Chandigarh Pharmacy College, Chandigarh Group of College, Jhanjeri, Mohali, Punjab, 140307, India

Department of Chemistry, Raghu Engineering College, Visakhapatnam, Andhra Pradesh, 531162, India

MRavi Kumar

School of Applied and Life Sciences, Division of Research and Innovation, Uttaranchal University, Dehradun, India

Aashna Sinha

Department of Biotechnology, Graphic Era (Deemed to Be University), Clement Town Dehradun, 248002, India

Department of Allied Sciences, Graphic Era Hill University Clement Town Dehradun, Clement Town Dehradun, 248002, India

Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar

Hashem Abu Serhan

Center for Global Health Research, Saveetha Medical College and Hospital, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India

Muhammed Shabil

Medical Laboratories Techniques Department, AL-Mustaqbal University, Hillah, Babil, 51001, Iraq

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Substantial contribution to the conception or design of the work: RI, AMG, MNK. Acquisition of data: MS-2, SB, PB.  Analysis and interpretation of data for the work: IA, MRK, AS, KP.  Drafting the work: HAS, M2. AS.  Revising it critically for important intellectual content: AAA, KP, MS, PB,SB, MRK.  Resources: AAA, HAS, MS, KP.  Final approval of the version to be published: All authors (AAA, RI, AMG, MNK, SB, PB, MS, IA, MRK, AS, KP, HAS, MS-2). Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: All authors (AAA, RI, AMG, MNK, SB, PB, MS, IA, MRK, AS, KP, HAS, MS-2).

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Correspondence to Abdelaziz A. Awad , Abhay M. Gaidhane or Hashem Abu Serhan .

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Awad, A.A., Itumalla, R., Gaidhane, A.M. et al. Association of electronic cigarette use and suicidal behaviors: a systematic review and meta-analysis. BMC Psychiatry 24 , 608 (2024). https://doi.org/10.1186/s12888-024-06012-7

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A systematic review of the effects of e-cigarette use on lung function

• Lucy Honeycutt 1 ,
• Katherine Huerne 1 , 2 ,
• Alanna Miller 1 ,
• Erica Wennberg 1 ,
• Kristian B. Filion 1 , 3 ,
• Roland Grad 1 , 4 ,
• Andrea S. Gershon 5 ,
• Carolyn Ells   ORCID: orcid.org/0000-0002-4593-454X 1 , 2 , 4 ,
• Genevieve Gore 6 ,
• Andrea Benedetti 3 , 7 ,
• Brett Thombs 1 , 3 , 8 &
• Mark J. Eisenberg   ORCID: orcid.org/0000-0002-1296-0661 1 , 3 , 9  

npj Primary Care Respiratory Medicine volume  32 , Article number:  45 ( 2022 ) Cite this article

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• Epidemiology

Given the increasing use of e-cigarettes and uncertainty surrounding their safety, we conducted a systematic review to determine the effects of e-cigarettes on measures of lung function. We systematically searched EMBASE, MEDLINE, and PsycINFO databases via Ovid, the Cochrane CENTRAL database, and the Web of Science Core from 2004 until July 2021, identifying 8856 potentially eligible studies. A total of eight studies (seven studying immediate effects and one long-term effects, 273 total participants) were included. The risk of bias was assessed using the Risk of Bias in Non-randomized Studies—of Interventions (ROBINS-I) and Cochrane risk of bias tools. These studies suggest that vaping increases airway resistance but does not appear to impact forced expiratory volume in one second (FEV 1) , forced vital capacity (FVC), or FEV 1 /FVC ratio. However, given the limited size and follow-up duration of these studies, larger, long-term studies are required to further determine the effects of e-cigarettes on lung function.

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Introduction.

The first electronic cigarette (e-cigarette) was patented and marketed in 2004 1 . Since then, e-cigarette use (or “vaping”) has grown exponentially across the globe 2 . As the use of vaping devices evolves with policy, the consequences of vaping on health are becoming an increasingly important public health issue. E-cigarettes are being studied for harm reduction in individuals who use cigarettes and as a smoking cessation aid, as they are believed to be less harmful to health than smoking 3 . However, there is increasing evidence demonstrating adverse respiratory effects of vaping compared to vaping abstinence. In particular, an outbreak of E-Cigarette and Vaping-Associated Lung Illness (EVALI) brought the short-term respiratory consequences of vaping into question, especially if cannabis or THC-containing products are used 4 . Other short-term respiratory changes that have been linked to vaping include increased airway resistance 5 , breathing difficulty 6 , and transient lung inflammation 7 . Vaping has also been associated with chronic respiratory conditions such as asthma 8 and chronic bronchitis 9 . Despite these reports, the short- and long-term respiratory safety of vaping is still largely unknown. Several small studies have examined the effects of e-cigarettes on lung function, including measures such as forced expiratory volume in one second (FEV 1 ), forced vital capacity (FVC), and airway resistance. However, no evidence syntheses have been completed on this topic. Therefore, we conducted a systematic review to determine the effects of vaping on measures of lung function.

Our systematic review was conducted following a protocol developed prior to initiating the review, which was registered on the PROSPERO register of systematic reviews ( CRD42021227121 ) 10 . This systematic review is reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines 11 .

Search strategy and study selection

Using a search strategy (Supplementary Tables 1 – 5 ) developed by an experienced health sciences librarian (G.G.), we systematically searched EMBASE, MEDLINE, and PsycINFO databases via Ovid, the Cochrane CENTRAL database, and the Web of Science Core from 2004 (the year of the first e-cigarette patent) until July 12, 2021. We additionally conducted a gray literature search by searching the websites of key governmental and public health organizations (the World Health Organization, Health Canada, the US Centers for Disease Control and Prevention, the US Food and Drug Administration, the Canadian Center on Substance Use and Addiction, the European Centre for Disease Prevention and Control, and the European Public Health Association). Additional articles were identified by manually searching the reference lists of included publications as well as SCOPUS and Google Scholar (first ten pages). Articles were included if they reported quantitative primary data on changes in lung function associated with vaping, defined as the use of any device that functions by transforming an e-liquid to an aerosol using metal coils, among human participants of any age. Studies of cells and those conducted in animals were excluded. Studies using heat-not-burn devices were also excluded, as these do not meet the above definition of vaping. Eligible studies included randomized controlled trials (RCTs), non-randomized studies of interventions (NRSIs), and cohort studies; cross-sectional studies and case reports were excluded. We included studies that used non-users of both vaping devices and conventional cigarettes as a comparison group and those that used a pre- and post-design in which individuals acted as their own controls. Inclusion was not restricted by language or country of publication. Abstracts and conference proceedings were included if sufficient data could be extracted from these publications.

Search results were downloaded from databases into reference management software (EndNote X9) or manually added (e.g., for gray literature results). Duplicates were removed in EndNote and entries were uploaded to Covidence (Veritas Health Innovation, Melbourne, Australia), a systematic review software. Two reviewers (L.H. and K.H.) independently screened the titles and abstracts of all identified publications for eligibility. Citations considered potentially eligible by either reviewer, based on the pre-specified review inclusion/exclusion criteria (Supplementary Table 6 ), were retrieved for full-text screening and assessed for inclusion. The reasons for exclusion after full-text review were annotated in Covidence and any disagreements were resolved by consensus or a third reviewer (A.H-L.).

Data extraction

Two independent reviewers (L.H and K.H.) extracted methodological, demographic, and outcome data from included studies in duplicate; disagreements were detected in Covidence and were resolved by consensus or, if necessary, by a third reviewer (A.H-L.). Extracted data included study characteristics (first author, journal, year of publication, years(s) of data collection, funding, data source, study design, recruitment strategy, duration of follow-up, country of origin, sample size); population characteristics (sex, gender, age, race, ethnicity, socioeconomic status, dose/frequency of e-cigarette use, conventional cigarette smoking status, smoked cannabis use); and vaping behavior, including the type of vaping device used (e.g., disposable e-cigarette vs. pod device such as JUUL), vaping products used (e.g., nicotine cartridges exclusively vs. THC cartridges exclusively vs. dual use of nicotine and THC products), and source of the vaping product (informal [i.e., friends, family members, or dealers] vs. commercial [i.e., vape shops, stores, dispensaries]).

Initially, extracted outcomes of primary interest were respiratory signs and symptoms, as these are important to patients and are the early signs of respiratory disease. Secondary outcomes included: findings on lung function; Computed tomography (CT) findings of emphysema, airway remodeling, and small airway loss; respiratory-related quality of life and exercise limitations; incidence and/or prevalence of respiratory disease as well as exacerbations of previous respiratory disease; and health care resource use including respiratory disease-related ambulatory care, emergency department visits, and hospitalization. Given the limited number of studies available and the heterogeneity of the data extracted from these studies, no meta-analysis was conducted.

Risk of bias

The risk of bias in included publications was assessed independently by two reviewers (L.H. and K.H.), and discrepancies were resolved by consensus or, if necessary, by a third reviewer (A.H-L.). The risk of bias of included non-randomized studies (pre-post studies, NRSI with non-vaping reference group, cohort study) was assessed using the Risk of Bias in Non-randomized Studies—of Interventions (ROBINS-I) tool 12 . The ROBINS-I tool evaluates intervention-specific outcomes for a study through seven domains which assess the risk of bias pre-intervention, at-intervention, and post-intervention. For each outcome of interest extracted from an included study, the risk of bias within each domain was reported as “low”, “moderate”, “serious”, or “critical”. Included RCTs were assessed using the Cochrane Collaboration’s Tool for Assessing Risk of Bias (ROB V1) 13 . Similar to ROBINS-I, this tool evaluates the risk of bias through the assessment of five domains; for each outcome of interest extracted from an included study, the risk of bias for each domain was reported as “low risk of bias”, “high risk of bias”, or “unclear risk of bias.” All eligible publications were included in the qualitative synthesis regardless of their assessed risk of bias.

Reporting summary

Further information on research design is available in the Nature Research Reporting Summary linked to this article.

As our search did not identify studies which focused on the broad outcomes detailed above, we chose to limit our focus to studies on lung function. Our database searches identified 14,307 potentially eligible studies (Fig. 1 ). After duplicates were removed, 8856 titles and abstracts were assessed. After this initial screening, 44 full texts were retrieved and reviewed in further detail, yielding eight studies eligible for inclusion.

PRISMA flow diagram of included studies assessing the effect of e-cigarettes on lung function.

Study and participant characteristics

Of the eight included studies (273 total participants), seven 14 , 15 , 16 , 17 , 18 , 19 , 20 involved short-term exposure to e-cigarettes with immediate outcome assessment, and the remaining study followed vapers and non-vapers over 3.5 years 21 (Table 1 ). This prospective cohort study examined 21 participants (12 nonsmokers and nine vapers) at means of 12 (standard deviation: 1), 24 (2), and 42 (2) months after baseline 21 . Of the seven short-term studies, four were NRSIs (three pre-post studies 14 , 15 , 16 and one NRSI with a non-vaping reference group 20 ) and three were RCTs 17 , 18 , 19 . Among these seven studies, two included 70–80 participants 14 , 15 and five included 10–30 participants 16 , 17 , 18 , 19 , 20 . Exposures varied in terms of e-cigarettes, e-liquids, and vaping session timings. Most studies did not expand on their definition of “non-smoker/non-vaper” 15 , 16 , 18 , 19 , 20 , 21 , but two studies clarified that these participants were never-smokers 14 , 17 . One of these two studies further elaborated that participants had no exposure to tobacco products or e-cigarettes 17 . Few studies gave detailed information on the type of e-cigarette used. Three studies reported a specific brand or product (Blu 17 , eGo 16 , Joytech elips-C series 18 , Puff bar 20 ). Polosa et al. listed some of the various e-cigarettes used by participants throughout the longitudinal study, including standard refillable (eGo style products) and more advanced refillable (Provari, Innokin, Joytech, eVIC, Avatar Puff) 21 . The remaining studies did not report a specific brand, though one study described the e-cigarette used as a “1 st generation e-cigarette popular in Greece” 15 . All studies clarified whether the e-cigarettes used during the study contained nicotine.

The included RCTs ( n  = 3) 17 , 18 , 19 had an unclear risk of bias, with each study demonstrating an unclear risk of bias in 3+ domains (Table 2 ). This was primarily due to missing information in the manuscripts required to make an adequate judgment, such as a lack of detail surrounding randomization. The risk associated with the blinding of participants and personnel was judged to be low for all 3 included RCTs. These studies were not blinded, and one was placebo-controlled. However, it was judged that this lack of blinding would not influence measures of lung function. Of the included non-randomized studies ( n  = 5) 14 , 15 , 16 , 20 , 21 , four 14 , 15 , 16 , 20 were judged to be at moderate risk of bias and one 21 was found to have a serious risk of bias (Table 3 ). The most consistent source of bias in these studies was bias due to confounding, with only one 16 study judged to have a low risk of bias due to confounding. Of the remaining four studies, three 14 , 15 , 20 were found to have a moderate risk of bias due to confounding and one 21 was found to be at serious risk of bias due to confounding, with important confounding variables not accounted for in the design or analysis.

Effects of E-cigarette use on lung function

Seven studies 14 , 15 , 16 , 17 , 18 , 19 , 20 reported immediate measures of lung function after short-term exposure to e-cigarettes (Table 4 ), including FEV 1 , FVC, and FEV 1 /FVC. Two studies, Boulay et al. and Staudt. et al. suggested no changes in FEV 1 or FEV 1 /FVC after vaping among nonsmokers 17 , 19 . Kizhakke Puliyakote et al. observed lower baseline FEV 1 and FEV 1 /FVC values among nonsmokers compared to vapers 20 . Coppeta et al. found a decrease in FEV 1 and FEV 1 /FVC among nonsmokers after 1 min of vaping; however, these values returned to baseline after 15 min 16 .

Airway resistance and specific airway conductance after 10 min of vaping were measured in two 14 , 15 of the seven short-term studies (Table 4 ). Both Palamidas et al. 2013 and 2017 suggested that vaping increased airway resistance and decreased specific airway conductance among nonsmokers and smokers with and without respiratory disease. Oxygen saturation was assessed in four studies 15 , 17 , 19 , 20 . Three studies suggested no changes after vaping, with only Palamidas et. al. 2017 suggesting decreased oxygen saturation following vaping among smokers with and without asthma 15 .

Long-term changes (3.5 years) in lung function measurements were assessed in only one small ( n  = 21) study (Polosa 2017) 21 . This study suggested that FEV 1 , FVC, FEV 1 /FVC, and forced mid-expiratory flow (FEF 25-75 ) did not change over time among vapers and non-vapers (Table 5 ).

This systematic review was designed to determine the effect of vaping on measures of lung function. We found that there were only eight studies in the literature assessing this issue, all of which were small, and only one examined longer-term outcomes (3.5 years follow-up). In general, these studies suggest that there are no acute changes associated with vaping. However, airway resistance and conductance may be influenced by e-cigarettes, with two studies reporting changes in these values in multiple population subgroups. It is important to note that there were few studies available for this systematic review and that most of these studies focused on the acute effects of vaping; therefore, these results are suggestive but not definitive, and future research must be conducted in this area. Furthermore, three of the included studies had an unclear risk of bias, four had a moderate risk of bias, and one had a serious risk of bias, which further limits the interpretation of this review’s findings.

In addition to the limitations above, this review lacks subgroup analyses or a meta-analysis. This is due to the heterogeneity of the included studies, both in terms of study design and outcomes. Few studies were eligible for this review due to the variation in study designs and definitions of e-cigarettes and smoking status. For example, some studies included both conventional cigarette smokers and nonsmokers in their definition of “non-vapers” and did not analyze data separately based on conventional smoking status. Other studies used a “sham” vaping session for controls where either an e-cigarette with an empty cartridge (i.e., without e-liquid) or second-hand smoke were used. More commonly, studies were conducted on smokers only, without nonsmokers as a comparison group. Future studies could analyze subgroups based on both smoking and vaping status to allow for a more detailed quantitative analysis.

E-cigarettes are becoming more popular for recreational use and are being studied for harm reduction among smokers as a smoking cessation aid, as they are believed to be less harmful to health than smoking. However, there are limited data available and virtually no long-term studies assessing how prolonged e-cigarette use could impact lung function. As the use of vaping devices evolves and becomes more widespread, the health consequences of vaping are becoming an increasingly important public health issue. This is a knowledge gap that must be addressed. Knowledge of the safety of e-cigarettes, particularly their long-term safety, will inform public health policy and e-cigarette regulations, as well as the guidance clinicians, offer to their patients on smoking harm reduction. For these policies, regulations, and guidelines to be developed, we must understand how e-cigarettes can influence one’s health. This includes establishing the effects of e-cigarettes on clinical outcomes such as respiratory symptoms (cough, dyspnea), measures of lung function, and risk of developing respiratory disease. Further research is required to elucidate the short- and long-term consequences of vaping to determine whether e-cigarettes are truly a “safer” alternative to traditional cigarettes for smoking cessation or for recreational use. Future studies should be long-term, have large sample sizes, and may include different types of e-cigarettes as well as conventional cigarettes for comparison. In addition, it is important for future research to include clinical outcomes as described above. This will allow for better translation of the research findings to help inform clinical decision-making.

Data availability

No additional data were available, as this study is a knowledge synthesis that relied on aggregate, published results available in the public domain. Any inquiries should be directed to the corresponding author.

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Acknowledgements

The authors would like to thank Jenna Glidden and Andrea Hebert-Losier for their assistance with study screening, data abstraction, and risk of bias assessment. The authors would also like to thank Francesca Frati, who peer-reviewed the search strategy. This work was funded by the Canadian Institutes for Health Research (#HEV-172891). The funder of the study had no role in study design, data collection, data analysis, data interpretation, writing of the report, or decision to submit for publication. Dr. Filion is supported by a Senior Research Scholar award from the Fonds de recherche du Québec – Santé and a William Dawson Scholar award from McGill University. Dr. Thombs was supported by a Tier 1 Canada Research Chair.

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Lucy Honeycutt, Katherine Huerne, Alanna Miller, Erica Wennberg, Kristian B. Filion, Roland Grad, Carolyn Ells, Brett Thombs & Mark J. Eisenberg

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Departments of Medicine and of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC, Canada

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Andrea S. Gershon

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Respiratory Epidemiology and Clinical Research Unit, Centre for Outcomes Research and Evaluation, Research Institute of the McGill University Health Centre, Montreal, QC, Canada

Andrea Benedetti

Departments of Psychiatry, Psychology, and Biomedical Ethics Unit, McGill University, Montreal, QC, Canada

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Division of Cardiology, Jewish General Hospital/McGill University, Montreal, QC, Canada

Mark J. Eisenberg

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Contributions

G.G. performed the search. L.H. and K.H. screened studies, extracted data, and performed a risk of bias assessment of included studies. L.H. drafted the manuscript. All authors contributed to the study design and interpretation of results, revised the manuscript for important intellectual content, and approved the final version of the manuscript. M.J.E. supervised the study and is the guarantor.

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Correspondence to Mark J. Eisenberg .

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Honeycutt, L., Huerne, K., Miller, A. et al. A systematic review of the effects of e-cigarette use on lung function. npj Prim. Care Respir. Med. 32 , 45 (2022). https://doi.org/10.1038/s41533-022-00311-w

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Youth Use of Nicotine Pouches Remains Low

Half a million fewer U.S. youth reported current use of e-cigarettes in 2024 compared to 2023, according to new data from the National Youth Tobacco Survey (NYTS) released today by the U.S. Food and Drug Administration and the U.S. Centers for Disease Control and Prevention. The nationally representative data featured in Morbidity and Mortality Weekly Report (MMWR) includes findings on e-cigarette and nicotine pouch use among U.S. youth, two categories of tobacco products the FDA and CDC are monitoring closely, particularly regarding youth use and appeal. 

NYTS is an annual school-based, self-administered survey of U.S. middle (grades 6–8) and high school (grades 9–12) students conducted Jan. 22 to May 22, 2024. Findings showed there was a significant drop in the number of U.S. middle and high school students who reported current (past 30 days) e-cigarette use – a decrease from 2.13 million (7.7%) youth in 2023 to 1.63 million (5.9%) youth in 2024. This decline was largely driven by reduced e-cigarette use among high schoolers (1.56 million to 1.21 million), with no statistically significant change in current e-cigarette use among middle school students within the past year. The number of youth who used e-cigarettes in 2024 is approximately one-third of what it was at its peak in 2019, when over five million youth reported current e-cigarette use.

“The continued decline in e-cigarette use among our nation’s youth is a monumental public health win,” said Brian King, Ph.D., M.P.H., director of the FDA’s Center for Tobacco Products. “This progress is a testament to the relentless efforts by the FDA, CDC and others, particularly over the past half decade. But we can’t rest on our laurels, as there’s still more work to do to further reduce youth e-cigarette use.” 

Among youth who currently used e-cigarettes, 26.3% reported using e-cigarettes daily. The vast majority of youth who currently used e-cigarettes used flavored products (87.6%), with fruit (62.8%), candy (33.3%) and mint (25.1%) being the top three most commonly used flavors. Disposable e-cigarette products were the most common product type used; however, the most popular brands included both disposable and cartridge-based products. Among youth who currently used e-cigarettes, the most commonly reported brands were Elf Bar (36.1%), Breeze (19.9%), Mr. Fog (15.8%), Vuse (13.7%) and JUUL (12.6%). 

Over the past year, a substantive drop occurred in youth reporting use of e-cigarette products under the Elf Bar brand - from 56.7% in 2023 to 36.1% in 2024. Elf Bar is not authorized by the FDA and has been the subject of focused compliance and enforcement actions by the agency since early 2023, including more than 1,000 warning letters and 240 civil money penalties to retailers and others in the supply chain. The FDA has also issued import alerts that include products under the Elf Bar brand, which places them on the “red list” and allows the agency to detain products without conducting a full inspection at the time of entry. 

“Youth use of tobacco products in any form—including e-cigarettes and nicotine pouches—is unsafe,” said Deirdre Lawrence Kittner, Ph.D., M.P.H., director of CDC’s Office on Smoking and Health. "It’s essential that we remain vigilant and committed to public health efforts to ensure all youth can live healthy, tobacco-free lives.”

Youth nicotine pouch use did not show a statistically significant change from 2023 (1.5% in 2023 and 1.8% in 2024). Of the nearly half a million middle and high school students who reported current nicotine pouch use, 22.4% used them daily. The most commonly reported brands among that group were Zyn (68.7%), on! (14.2%), Rogue (13.6%), Velo (10.7%) and Juice Head ZTN (9.8%). Among those who currently used nicotine pouches, the vast majority used flavored products (85.6%), with mint (53.3%), fruit (22.4%) and menthol (19.3%) being the most commonly used flavors. 

“While it’s encouraging to see these numbers currently remaining relatively low, the bottom line is that we are concerned about any youth appealing tobacco product,” King said. “Our guard is up. We are aware of the reported growing sales trends for nicotine pouches and are closely monitoring the evolving tobacco product landscape for threats to public health, particularly when it comes to kids.” 

Keeping tobacco products out of the hands of youth remains a top priority for the FDA and CDC. As students head back to school, it is important for educators and parents to talk to teens about tobacco product use. The FDA and CDC have free information and resources available to assist these and other groups. For example, the FDA’s Vaping Prevention and Education Resource Center is an online hub with free science-based lesson plans and materials for teachers and parents to promote learning and conversations about youth tobacco product use. The FDA’s “ The Real Cost ” Youth E-Cigarette Prevention campaign also continues to reach approximately 90% of U.S. teens with its effective prevention messages. Additionally, CDC offers a suite of resources to help protect youth from the harms of vaping and other tobacco product use, including its “Empower Vape-Free Youth” campaign for middle and high school educators.

Related Information

• Morbidity and Mortality Weekly Report, Sept. 5, 2024
• Results from the Annual National Youth Tobacco Survey

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More than 2.5 Million Youth Reported E-Cigarette Use in 2022

Flavored products, disposable devices, and a wide variety of brands threaten the health of our nation’s youth

Embargoed Until: Thursday, October 6, 2022, 1:00 p.m. ET Contact: Media Relations (404) 639-3286

A  study  released today from the U.S. Food and Drug Administration and the U.S. Centers for Disease Control and Prevention (CDC) found that 2.55 million U.S. middle and high school students reported current (past 30-day) e-cigarette use in 2022, which includes 14.1% of high school students and 3.3% of middle school students. Nearly 85% of those youth used flavored e-cigarettes and more than half used disposable e-cigarettes.

Among youth who currently used e-cigarettes, 14.5% reported their usual brand was Puff Bar, followed by Vuse (12.5%), Hyde (5.5%), and SMOK (4.0%); more than one fifth (21.8%) reported their usual brand was a brand other than the 13 listed in the survey.

The findings, published in the  Morbidity and Mortality Weekly Report , are based on data from the 2022 National Youth Tobacco Survey (NYTS), a cross-sectional, self-administered survey of U.S. middle (grades 6–8) and high (grades 9–12) school students, which was administered January 18–May 31, 2022. The study assessed current use (on one or more of the past 30 days) of e-cigarettes; frequency; and use by device type, flavors, and usual brand.

“This study shows that our nation’s youth continue to be enticed and hooked by an expanding variety of e-cigarette brands delivering flavored nicotine,” said Deirdre Lawrence Kittner, Ph.D., M.P.H., director of CDC’s Office on Smoking and Health. “Our work is far from over. It’s critical that we work together to prevent youth from starting to use any tobacco product – including e-cigarettes – and help all youth who do use them, to quit.”

Other Key Findings

• Frequency of Use: Among youth who currently used e-cigarettes, more than one in four (27.6%) used them daily and more than four in 10 (42.3%) used them on 20 or more of the past 30 days.
• Device Type: Among youth who currently used e-cigarettes, the most commonly used e-cigarette device type was disposable (55.3%), followed by prefilled or refillable pods or cartridges (25.2%), and tanks or mod systems (6.7%). Additionally, 12.8% reported not knowing the type of device used.
• Flavored E-cigarettes: Among youth who currently used e-cigarettes, 84.9% used flavored e-cigarettes, i.e., with flavors other than tobacco, including 85.5% of high school and 81.5% of middle school students reporting use. Overall, the most used flavors were fruit (69.1%); candy, desserts, or other sweets (38.3%); mint (29.4%); and menthol (26.6%).

“Adolescent e-cigarette use in the United States remains at concerning levels, and poses a serious public health risk to our nation’s youth,” said Brian King, Ph.D., M.P.H., director of the FDA’s Center for Tobacco Products. “Together with the CDC, protecting our nation’s youth from the dangers of tobacco products—including e-cigarettes—remains among the FDA’s highest priorities, and we are committed to combatting this issue with the breadth of our regulatory authorities.”

Due to changes in methodology, including differences in survey administration and data collection procedures in recent years due to the COVID-19 pandemic, the ability to compare estimates from 2022 with those from prior NYTS waves is limited; differences between estimates might be due to changes in methodology, actual behavior, or both.

Addressing Youth Tobacco Product Use

Youth use of tobacco products in any form, including e-cigarettes—is unsafe. Such products contain nicotine, which is highly addictive and can harm the developing adolescent brain. Using nicotine during adolescence might also increase risk for future addiction to other drugs.

Since 2014, e-cigarettes have been the most used tobacco product among U.S. youth. As the tobacco product landscape continues to change, the sustained implementation of comprehensive tobacco prevention and control strategies at the national, state, and local levels, coupled with FDA regulations, is critical to prevent and reduce youth access to and use of e-cigarettes.

For additional information, including quit resources, visit:

• Quick Facts on the Risks of E-cigarettes for Kids, Teens, and Young Adults | CDC
• Smokefree.gov

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NIH-funded studies show damaging effects of vaping, smoking on blood vessels

Combining e-cigarettes with regular cigarettes may increase health risks     

Long-term use of electronic cigarettes, or vaping products, can significantly impair the function of the body’s blood vessels, increasing the risk for cardiovascular disease. Additionally, the use of both e-cigarettes and regular cigarettes may cause an even greater risk than the use of either of these products alone. These findings come from two new studies supported by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH).  

The findings, which appear today in the journal Arteriosclerosis, Thrombosis, and Vascular Biology , add to growing evidence that long-term use of e-cigarettes can harm a person’s health. Researchers have known for years that tobacco smoking can cause damage to blood vessels. However, the effects of e-cigarettes on cardiovascular health have been poorly understood. The two new studies – one on humans, the other on rats – aimed to change that.

“In our human study, we found that chronic e-cigarettes users had impaired blood vessel function, which may put them at increased risk for heart disease,” said Matthew L. Springer, Ph.D., a professor of medicine in the Division of Cardiology at the University of California in San Francisco, and leader of both studies. “It indicates that chronic users of e-cigarettes may experience a risk of vascular disease similar to that of chronic smokers.” 

In this first study, Springer and his colleagues collected blood samples from a group of 120 volunteers that included those with long-term e-cigarette use, long-term cigarette smoking, and those who didn't use. The researchers defined long-term e-cigarette use as more than five times/week for more than three months and defined long-term cigarette use as smoking more than five cigarettes per day.

They then exposed each of the blood samples to cultured human blood vessel (endothelial) cells in the laboratory and measured the release of nitric oxide, a chemical marker used to evaluate proper functioning of endothelial cells. They also tested cell permeability, the ability of molecules to pass through a layer of cells to the other side. Too much permeability makes vessels leaky, which impairs function and increases the risk for cardiovascular disease.

The researchers found that blood from participants who used e-cigarettes and those who smoked caused a significantly greater decrease in nitric oxide production by the blood vessel cells than the blood of nonusers. Notably, the researchers found that blood from those who used e-cigarettes also caused more permeability in the blood vessel cells than the blood from both those who smoked cigarettes and nonusers. Blood from those that used e-cigarettes also caused a greater release of hydrogen peroxide by the blood vessel cells than the blood of the nonusers. Each of these three factors can contribute to impairment of blood vessel function in people who use e-cigarettes, the researchers said.

In addition, Springer and his team discovered that e-cigarettes had harmful cardiovascular effects in ways that were different from those caused by tobacco smoke. Specifically, they found that blood from people who smoked cigarettes had higher levels of certain circulating biomarkers of cardiovascular risks, and the blood people who used e-cigarettes had elevated levels of other circulating biomarkers of cardiovascular risks.

“These findings suggest that using the two products together, as many people do, could increase their health risks compared to using them individually,” Springer said.  “We had not expected to see that.”

In the second study, the researchers tried to find out if there were specific components of cigarette smoke or e-cigarette vapor that were responsible for blood vessel damage. In studies using rats, they exposed the animals to various substances found in tobacco smoke or e-cigarettes. These included nicotine, menthol (a cigarette additive), the gases acrolein and acetaldehyde (two chemicals found in both tobacco smoke and e-cigarette vapors), and inert carbon nanoparticles to represent the particle-like nature of smoke and e-cigarette vapor.

Using special arterial flow measurements, the researchers demonstrated that blood vessel damage does not appear to be caused by a specific component of cigarette smoke or e-cigarette vapor. Instead, they said, it appears to be caused by airway irritation that triggers biological signals in the vagus nerve that somehow leads to blood vessel damage, possibly through an inflammatory process. The vagus is a long nerve extending from the brain that connects the airway to the rest of the nervous system and plays a key role in heart rate, breathing, and other functions. The researchers showed that detaching the nerve in rats prevented blood vessel damage caused by tobacco smoke, demonstrating its key role in this process. 

“We were surprised to find that there was not a single component that you could remove to stop the damaging effect of smoke or vapors on the blood vessels,” Springer said. “As long as there’s an irritant in the airway, blood vessel function may be impaired.”   

The finding has implications for efforts to regulate tobacco products and e-cigarettes, as it underscores how difficult it is to pinpoint any one ingredient in them that is responsible for blood vessel damage. “What I like to tell people is this: Just breathe clean air and avoid using these products,” Springer said.

Lisa Postow, Ph.D., an NHLBI program officer in NHLBI’s Division of Lung Diseases, agreed that the study results “provide further evidence that exposure to e-cigarettes could lead to harmful cardiovascular health effects.” She added that more data is needed to fully understand the health effects of e-cigarettes. The NIH and others are continuing to explore this area.

Research reported in the e-cigarette study was funded by NHLBI grants U54HL147127, P50HL120163, and R01HL120062 and the U.S. Food and Drug Administration Center for Tobacco Products (FDA CTP); and grant P50CA180890 from the National Cancer Institute at the NIH and FDA CTP. Research reported in the cigarette smoke/-vagal nerve study was supported by NHLBI grants R01HL120062 and U54HL147127 and FDA CTP and grant P50CA180890 from the National Cancer Institute at the NIH and FDA CTP. For additional funding details, please see the full journal articles.

Study: Chronic e-cigarette use impairs endothelial function on the physiological and cellular levels. Arteriosclerosis, Thrombosis, and Vascular Biology.  DOI: 10.1161/ATVBAHA.121.317749

Study:  Impairment of Endothelial Function by Cigarette Smoke is not Caused by a Specific Smoke Constituent, but by Vagal Input from the Airway. Arteriosclerosis, Thrombosis, and Vascular Biology. DOI: 10.1161/ATVBAHA.122.318051

About the National Heart, Lung, and Blood Institute (NHLBI):  NHLBI is the global leader in conducting and supporting research in heart, lung, and blood diseases and sleep disorders that advances scientific knowledge, improves public health, and saves lives. For more information, visit  www.nhlbi.nih.gov .

About the National Institutes of Health (NIH):  NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit  www.nih.gov .

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Largest US study of e-cigarettes shows their value as smoking cessation aid

E-cigarettes do have value as a smoking cessation aid, according to a new study just released by a team of MUSC Hollings Cancer Center  researchers.

Whether e-cigarettes should be considered for smoking cessation is a hotly debated topic, and different countries have taken different approaches. E-cigarettes contain harmful chemicals, which has led many public health advocates to shun them. But they are less harmful than traditional cigarettes, which can cause a dozen types of cancer as well as heart disease, stroke, diabetes and chronic obstructive pulmonary disease. That’s prompted others to say that e-cigarettes should be considered as a step-down method for adults who smoke and haven’t been able to quit using FDA-approved aids, like nicotine replacement gum, lozenges or patches. This new study, the largest trial of e-cigarettes in the U.S., showed that e-cigarette usage nudged people toward quitting smoking – even people who had entered the trial saying they had no intention of quitting. The results were published in eClinical Medicine this month. “This is not a panacea for smoking cessation,” cautioned Matthew Carpenter, Ph.D. , first author on the paper and co-leader of the Cancer Control Research Program  at Hollings.

"No matter how we looked at it, those who got the e-cigarette product demonstrated greater abstinence and reduced harm as compared to those who didn’t get it." Matthew Carpenter, Ph.D.

Nonetheless, he was surprised to find that all of the hypotheses tested in the study were confirmed. “It’s rarely the case that you’re proven correct for almost everything that you predicted,” he said. “Here, it was one effect after another: No matter how we looked at it, those who got the e-cigarette product demonstrated greater abstinence and reduced harm as compared to those who didn’t get it.” Carpenter and his colleagues, including Hollings members Tracy Smith, Ph.D. , Jennifer Dahne, Ph.D. , Michael Cummings, Ph.D. , and Graham Warren, M.D., Ph.D. , designed the study in a naturalistic way to mimic real-world conditions as much as possible – also a first for e-cigarette studies. Previous studies that have shown a smoking cessation benefit of e-cigarettes have been very structured, Carpenter said, in that they recruited people who wanted to stop smoking and gave them very detailed instructions about how to use the e-cigarettes. “Some people have said, ‘That’s fine, but the results of those studies don't apply to the real world because the real world isn’t as structured,’” he explained. “So what we did was take a hands-off approach – we called it a naturalistic approach.” “First off, we took smokers who did and did not want to quit. So right off the bat, not everybody wanted to quit. Secondly, we gave them very little instruction on how to use it,” he continued. Instead, people were given e-cigarettes and told they could use them or not, as much or as little as they wanted. A control group didn’t receive anything.

"No one wants e-cigarettes in the hands of kids, and we should do all we can to stop that. But we shouldn’t do so by denying this option for adult smokers who can’t otherwise quit." Matthew Carpenter, Ph.D.

The study showed that people in the e-cigarette group were more likely to report complete abstinence from combustible cigarettes. They were also more likely to report that they’d reduced the number of cigarettes per day that they smoked and their number of “quit attempts.” Quit attempts are an important metric because people usually need multiple tries before they can successfully stop smoking. The study included people from 11 cities across the U.S. and spanned four years. At the beginning, Carpenter intended to collect biochemical samples from participants in the Charleston area to verify their self-reports of smoking behavior. However, COVID interrupted that plan and made in-person sample collection impossible. Although that was a disappointing aspect of the study, replying on participants’ self-reports of their smoking behavior is still considered highly reliable, he said. The study will be another data point for the public health community and policymakers in deciding how to handle e-cigarettes. “No one wants e-cigarettes in the hands of kids, and we should do all we can to stop that. But we shouldn’t do so by denying this option for adult smokers who can’t otherwise quit,” Carpenter said. He noted that other countries have taken a much more liberal approach to e-cigarette use than the U.S. For example, in April the U.K. announced a “Swap to Stop” program that will distribute vaping starter kits to 1 million people who smoke. In the U.S., e-cigarettes are not approved as smoking cessation aids. But Carpenter and Smith have just received funding for a study that will test e-cigarettes as a smoking cessation aid for adult smokers who’ve already tried two different FDA-approved methods. And Benjamin Toll, Ph.D ., director of the MUSC Health Tobacco Treatment Program, co-authored a commentary this month urging an education campaign for adult smokers to clarify that, while neither option is “safe,” traditional cigarettes are far more harmful than e-cigarettes.

Quitting for Good

If a first try at quitting smoking doesn't work, should the same method be tried again? Or a new method? Hollings researchers are seeking answers.

Vaping Misinformation

Dr. Benjamin Toll, director of the Tobacco Treatment Program, has been dismayed that so many misunderstand the continuum of risk for tobacco products.

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Smoking cessation counselors at Hollings focus on the positive changes their clients are making, providing nurturing support and evidence-based strategies.

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Leslie Cantu MUSC Hollings Cancer Center

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Assessing the FDA’s latest moves on nicotine and e-cigarettes

July 26, 2022—In June, the U.S. Food and Drug Administration announced plans to develop a proposed product standard by May 2023 that would establish a maximum nicotine level in combustible tobacco products and reduce their addictiveness. The same month, the agency ordered electronic cigarette company Juul to immediately stop selling its products in the U.S., but later suspended the order pending further review. And on July 13, the FDA announced that any new synthetic nicotine product that has not received premarket authorization from the agency cannot be legally marketed. Here, experts from Harvard T.H. Chan School of Public Health discuss the public health implications of these actions.

On the potential standard lowering nicotine levels

Howard Koh , Harvey V. Fineberg Professor of the Practice of Public Health Leadership: The historic product standard announcement creates critical forward momentum for a comprehensive nicotine-based tobacco regulatory plan FDA first pledged in 2017. The tobacco industry has long argued that use of their combustible products is about choice, not dependence, when of course the opposite has been true until now. Their cigarette products cause death in half of long-term users.

Having a marketplace featuring minimally- or non-addictive cigarettes with very low levels of nicotine could dramatically reduce addiction and associated suffering. Research models project that the new policy, when implemented, could prompt 13 million smokers to quit over five years, prevent more than 33 million youth and young adults from become regular smokers this century, and save more than eight million lives.

Vaughan Rees , senior lecturer on social and behavioral sciences and director, Center for Global Tobacco Control : Lowering nicotine in cigarettes to minimize their addictive potential makes good sense from a public health perspective. The evidence has shown that very low nicotine content (VLNC) cigarettes not only help to prevent young people becoming addicted but can reduce consumption and increase quitting in adult smokers.

There have been concerns that smokers who switch to VLNC cigarettes might puff more intensively or smoke more cigarettes to obtain the nicotine they need to satisfy their needs. This could result in an unintended consequence of even greater exposure to tobacco smoke toxicants. However, the evidence is clear that smokers who switch to VLNC cigarettes reduce their consumption and overall exposure to harmful tobacco smoke constituents, including certain carcinogens. Some smokers are finding that quitting is easier after transitioning from a VLNC product.

On decisions around regulation of Juul and synthetic nicotine

Rees: While the FDA is rightly working to protect a new generation of young people from becoming dependent on nicotine products, the decision to deny marketing authorization for Juul appears very shortsighted. Properly regulated, “clean” nicotine products, including Juul, have been shown to be a far less risky alternative to combustible cigarettes for adult smokers who have not been able to quit smoking. There are numerous strategies already in place to lower demand and restrict youth access to vaping products. However, removing a potentially life-saving option for some three million former adult smokers—while allowing combustible cigarettes to remain in the market—is not consistent with the principles of public health.

On the other hand, the attempt by some e-cigarette manufacturers to subvert FDA’s authority with synthetic nicotine product is a major concern. While synthetic nicotine products may not necessarily pose different health risks from other reduced exposure products, a lack of regulatory oversight of their sale and marketing, including health claims, could have serious consequences. Ultimately, Congress may need to update the law that provides FDA with its authority to regulate tobacco products by explicitly including synthetic nicotine.

Koh: Many scientific issues about Juul still need to be addressed so we await further FDA review. While a number of teens have moved away from e-cigarettes, it’s estimated that about two million youth in the U.S. use them over a 30-day period. Any action to protect kids from using e-cigarettes or any tobacco product during a vulnerable period of their lives will represent a major public health benefit.

On the way forward

Koh: I had the honor of attending, on my very first day as U.S. Assistant Secretary for Health in 2009, President Obama’s signing of the Family Smoking Prevention and Tobacco Control Act establishing the FDA Center for Tobacco Products. Since then, progress has been uneven and never easy. Recently however, the FDA is finally accelerating efforts for regulation of combustible products, like cigarettes, as well as non-combustible products, like e-cigarettes. Their actions regarding synthetic nicotine close a regulatory loophole that had existed until now. Moreover, along with the plan to move forward on a tobacco product standard for nicotine, the FDA recently announced major actions to ban menthol cigarettes and flavored cigars. Complicating all these issues, however, has been a tobacco industry publicly promoting the legitimate and critical concept of harm reduction while still producing combustible cigarettes that cause the harm in the first place. We need all forces to align together at this critical moment to save lives from a global pandemic that has gone on for far too long.

Rees: I am always optimistic about the potential for insightful scientists and policy makers to reduce the burden of tobacco-related disease. However, I am concerned that the FDA’s current stance on vaping products may unintentionally perpetuate disparities in tobacco-related harm. Although the prevalence of smoking has declined in the U.S., we have seen little change in smoking among marginalized groups.

I would like to see greater emphasis on a tobacco harm reduction approach, which would support adult smokers who are unable or unready to quit, to switch to reduced-exposure nicotine products. At the same time, regulatory authorities such as the FDA should continue to examine all possible options to regulate the features of combustible cigarettes that make them so deadly and work to transition to less deadly, smoke-free alternatives. Tobacco harm reduction has been adopted with success in the U.K., and the U.S. public—especially those who are at the highest risk of tobacco-related disease—deserve the opportunity to access properly regulated, low-risk alternative products, including vape devices.

— Amy Roeder

Photo: iStock/Juanmonino

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July 17, 2023

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Current evidence identifies health risks of e-cigarette use, long-term research needed

by American Heart Association

Research increasingly reveals health risks of e-cigarette use, and more studies are needed about the long-term impact e-cigarettes may have on the heart and lungs, according to a new scientific statement from the American Heart Association published in the journal Circulation .

The statement, "Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products," details the latest usage data and trends, identifies current health impacts, highlights existing basic and clinical scientific evidence surrounding e-cigarettes and recommends research priorities to further understand the short- and long-term health effects of e-cigarette use.

Vaping products, also known as e-cigarettes, are battery-operated systems that heat a liquid solution, or e-liquid, to create an aerosol that is inhaled into the lungs. Most e-liquid formulations deliver nicotine, which has been established as having negative health effects as well as strong addictive properties.

The products may also contain other substances, most commonly tetrahydrocannabinol (THC), the psychoactive element of cannabis, as well as methamphetamine, methadone or vitamins. The liquids also include humectants (hygroscopic carriers such as propylene glycol and vegetable glycerol) that act as solvents and create a water aerosol or vapor, flavoring agents, cooling agents such as menthol and sweeteners, in addition to metals from the heating coil and other chemicals.

"E-cigarettes deliver numerous substances into the body that are potentially harmful, including chemicals and other compounds that are likely not known to or understood by the user. There is research indicating that nicotine-containing e-cigarettes are associated with acute changes in several hemodynamic measures, including increases in blood pressure and heart rate ," said the volunteer chair of the scientific statement writing committee Jason J. Rose, M.D., M.B.A., an associate professor of medicine at the University of Maryland School of Medicine in Baltimore.

"There has also been research indicating that even when nicotine is not present, ingredients in e-cigarettes, particularly flavoring agents, independently carry risks associated with heart and lung diseases in animals. Negative effects of e-cigarettes have been shown through in vitro studies and in studies of individuals exposed to chemicals in commercially available products."

The writing committee points to the significance of the clinical diagnosis of "E-cigarette, or Vaping, product use Associated Lung Injury" (EVALI). EVALI was first recognized as a condition by the U.S. Centers for Disease Control and Prevention in 2019, when approximately 2,800 hospitalizations occurred among e-cigarette users in less than a year. This is cited in the statement as one example that emphasizes the lack of knowledge surrounding the risks of e-cigarettes and their ingredients.

In the case of the EVALI hospitalizations, vitamin E acetate has been implicated as the ingredient likely causing illness. This substance is used as a thickening agent in some e-cigarette liquids.

Studies gauging the specific impact e-cigarettes have on heart attacks and strokes are limited. Much research on e-cigarette use has been conducted in people who have also used or were currently using traditional cigarettes. Additionally, large survey studies have focused on younger adults who have a low occurrence of heart attacks and strokes. The writing committee says longer-term studies of e-cigarettes users of all ages are needed, including among people who already have cardiovascular disease.

One recent analysis of the adult Population Assessment of Tobacco and Health (PATH) study found a statistically significant association between former or current e-cigarette use at the time participants enrolled in the study and the development of incident respiratory disease (chronic obstructive pulmonary disease/COPD, chronic bronchitis, emphysema or asthma) within the next two years. The PATH Study, an ongoing study that started in 2013, is one of the first large tobacco research efforts undertaken by the National Institutes of Health and the U.S. Food and Drug Administration.

Additional studies cited in the statement indicate a rapid increase since 2010 in the number of people who had ever used e-cigarettes or were currently using the devices, and most of those users were current or former traditional cigarette smokers. In addition, by 2016, data from the Behavioral Risk Factor Surveillance System indicated about 1.2 million adults in the U.S. who had never smoked combustible cigarettes before were currently using e-cigarettes.

The writing committee noted that e-cigarettes are reported to be the most commonly used tobacco product among youth, particularly high school and middle school students. The statement cites data showing that almost three out of four young people using e-cigarettes exclusively report using flavored e-cigarette products. This high rate of use by youth makes it critical to assess the short- and long-term health effects of these products, according to the statement.

"Young people often become attracted to the flavors available in these products and can develop nicotine dependence from e-cigarette use. There is significant concern about young people assuming e-cigarettes are not harmful because they are widely available and marketed to an age group that includes many people who have never used any tobacco products," Rose said.

"The long-term risks of using e-cigarettes are unknown, but if the risks of chronic use are like combustible cigarettes, or even if the risks are reduced but still present, we may not observe them for decades. What is equally concerning is that studies show that some youth who use e-cigarettes go on to use other tobacco products, and there is also a correlation between e-cigarette use and substance use disorders."

Given the established, high health risks of smoking combustible cigarettes, e-cigarette products have been evaluated as smoking cessation tools. The writing committee examined the limited research in this area and concluded that any benefits e-cigarettes may offer to help people stop smoking or stop using tobacco products needs to be clearly balanced alongside the products' known and unknown potential health risks, including the known risk of long-term dependence on these products.

"E-cigarette companies have suggested that their products are a way to quit smoking traditional cigarettes. There is no strong evidence to support this beyond any short-term benefit. The lack of long-term scientific safety data on e-cigarette use, along with the potential for the addiction to e-cigarette products seen among youth, are among the reasons the American Heart Association does not recommend e-cigarette use for cessation efforts," said Rose Marie Robertson, M.D., FAHA, the Association's deputy chief science and medical officer and co-director of the Association's Tobacco Center of Regulatory Science.

"It's also important to note that e-cigarette products are not approved by the U.S. Food and Drug Administration (FDA) for tobacco cessation. The Association recommends a combination of multiple-episode cessation counseling accompanied by personalized nicotine replacement therapy with FDA-approved doses and formulations, as well as medications to help control cravings, to help people who smoke combustible cigarettes with cessation. And all of this needs to be undertaken with the understanding that quitting often takes many tries, and any failures should be seen as just episodes to learn from on the road to finally beating a powerful addiction for good."

The scientific statement writing committee emphasizes a critical need for additional knowledge and research, specifically:

• Future research should focus on gaining knowledge about serious and potentially long-term effects of e-cigarettes on the heart, blood vessels and lungs.
• Studies are needed that include patients with pre-existing cardiopulmonary disease, such as coronary artery disease or chronic obstructive pulmonary disease , to evaluate and compare outcomes among e-cigarette users in comparison to traditional smokers, and those who use e-cigarettes along with traditional cigarettes (referred to as dual users) and nonsmokers.
• More in-depth research is needed about the common chemical ingredients in e-cigarettes and the effects they independently have on pulmonary and cardiac health.
• Clinical studies are needed to study the risks and potential benefits of e-cigarettes as alternatives to traditional combustible cigarettes.
• Since the long-term health impact of e-cigarettes may take decades to emerge, more molecular and laboratory studies are needed in the interim to help determine the biological implications of e-cigarette use .

"Because e-cigarettes and other vaping systems have only been in the U.S. for about 15 years, we do not yet have enough information on their long-term health effects, so we must rely on shorter term studies, molecular experiments and research in animals to try to assess the true risk of using e-cigarettes," Jason Rose added. "It is necessary for us to expand this type of research since the adoption of e-cigarettes has grown exponentially, especially in young people, many of whom may have never used combustible cigarettes."

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Schools are putting vape detectors in bathrooms — paid for by Juul

Scott Neuman

A young woman vapes an electronic cigarette. Some districts are installing high-tech vape detectors to alert school officials if students are using e-cigarettes. whitebalance.oatt/Getty Images hide caption

E-cigarette use among young people in the U.S. dropped significantly over the past year, according to a new government study. The hopeful signs come as more schools are installing high-tech vape detectors in bathrooms and locker rooms to curb student use of e-cigarettes.

Some districts are using money from a $1.7 billion legal settlement against e-cigarette manufacturer Juul Labs to pay for the devices. But there’s disagreement over whether monitors are the best way to address the problem, and they have raised some privacy concerns.

E-cigarette use is declining — even as the industry eyes teens for new products

Nearly 1.63 million, or 6%, of high school and middle school students reported using e-cigarettes in 2024, compared with 2.13 million, or 7.7%, the previous year, according to the 2024 Annual National Youth Tobacco Survey .

The U.S. Food and Drug Administration says the long-term effects of vaping are not understood, but that for teens, nicotine-related changes in the brain may affect attention, learning and memory.

“We see students who would never touch a cigarette, because that's something that their parents or grandparents did,” says Michelle Mercure, the director of nationwide tobacco programs for the American Lung Association. Kids “see these products that are … tech friendly and that are flavored and those products are being marketed to them. And, unfortunately, a lot of them are … becoming addicted.”

A legal settlement with e-cigarette maker helps pay for vape detectors

In 2022, Juul settled some 5,000 lawsuits from states, counties and school districts that alleged that the e-cigarette maker used deceptive marketing aimed at teens and neglected to prevent underage sales of its products. Since then, additional suits have been settled. Money from those settlements has been used by schools from Spokane, Wash., to Orlando, Fla. , to install vape detectors.

Shots - Health News

Young adults who started vaping as teens still can't shake the habit.

“Ultimately, we are supportive of all actions that demonstrably combat underage use of any tobacco product, including vapor products,” a Juul spokesperson said.

The vape detectors, which resemble home smoke detectors and cost about $1,000 each, send an email or text message to school officials every time vape smoke is detected — including cannabinoid THC or CBD. They also detect loud noises that might indicate a fight has broken out and can signal staff if someone tampers with them. Vape detectors are often integrated with security cameras in halls and other public areas, so if a staff member can’t respond immediately, they might still be able to identify a student who has been vaping.

The Lincoln Public Schools district in Nebraska received about $1 million from the Juul settlement and is using the money to install vape detectors in its high schools and, eventually, the middle schools.

As part of a pilot program launched last year, the district put the devices in restrooms and locker rooms at Lincoln East High School. It didn't take long for vaping violations to decrease, says Ryan Zabawa, the district’s director of student services. In the first week of activation in October 2023, school officials received nearly 100 vaping alerts. By Christmas break, that number had dropped to just four. The district has since installed detectors in a second high school.

What's Zyn, and why there was a shortage this summer

“It absolutely is a deterrent,” Zabawa says. Without the detectors, policing the restrooms and locker rooms for vaping was a “cat and mouse” game, he says. “Kids were doing it, but you couldn't prove it. And you really wanted to try and get it stopped.”

School officials are concerned about the health of students, and they don’t want them breaking the law. The federal minimum age for purchasing tobacco products, including vapes, is 21.

Students caught vaping often face suspension

Lincoln East senior Blake Gronewold estimates that 10% to 15% of his classmates regularly vape, “usually in the bathrooms, sometimes in the hallways and the stairwells or, if they are really bold, class.”

Fellow senior Elizabeth Mason says since the detectors went in last year, she’s noticed far fewer “groups of people just hanging out in the bathroom.”

“It's like the people in there are actually in there for the right purposes,” she says.

Students who trigger an alert are searched, and if a vape device is found, they face suspension and are required to take a vape-awareness course, Zabawa says.

While some school districts are experimenting with pilot programs, a bipartisan group of lawmakers in New York recently introduced legislation that would require the city’s Department of Education to put detectors in every public school.

Councilwoman Joann Ariola sees the legislation as a first step toward intervention for students. She also hopes that a crackdown in schools will help thwart the illegal sales of e-cigarettes.

“We get calls all the time about stores that are selling vapes illegally to minors,” she says. “These minors are using those vapes while they're in school, while they're at playgrounds. Parents are absolutely concerned, and rightly so.”

They're illegal. So why is it so easy to buy the disposable vapes favored by teens?

Leslie Ricciardelli, the superintendent for Florida’s Collier County Public Schools, acknowledges that some students will vape off campus regardless of the school’s approach to the problem. If parents “permit it at home, that's their choice,” she says.

After a successful pilot project that saw an 80% drop in alerts over the course of the 2022-2023 school year, the district plans to deploy detectors in all of its high schools. Ricciardelli takes a no-nonsense approach with students who get caught. “The consequences are heavy,” she says. A first-time offense with nicotine results in a suspension. A second offense — or a first when a marijuana product is involved — will land the student in an alternative school.

Some favor education over punishment

But not everyone thinks the punitive approach is the right one. The American Lung Association’s Mercure oversees the organization’s “Vape-Free Schools Initiative,” a program that focuses on education and tries to help students quit.

“Students get caught and then they’re suspended,” Mercure says. The detectors make school officials feel like the problem can be solved without addressing the underlying issues.

“Some schools have already purchased those detectors,” she says. “Are we telling them to return them? No. But if they are using them, we would encourage them to make sure that they're addressing [the issue] more broadly than just using the vape detectors.”

The U.S. Food and Drug Administration says long-term effects of vaping are not understood, but that for teens, nicotine-related changes in the brain may affect attention, learning and memory. SolStock/Getty Images hide caption

School officials who talked to NPR acknowledge that they sometimes get “false positives” from substances such as perfume.

Lincoln East High’s Mason spoke of a classmate who says her spray deodorant set off one of the vape detectors. “I don't think she's the type to vape,” Mason says. Nonetheless, “she got pulled out” and searched.

IPVideo Corp. makes the HALO brand system used in the Lincoln school district. According to David Antar, head of HALO product sales at parent company Motorola Solutions, its line of detectors launched about six years ago and sales have spiked as schools use Juul settlement money to install the detectors.

Antar says the HALO system is 93% accurate and that false positives are rare. If students blow vape smoke into a plastic drink bottle or their clothes to evade detection, it normally just “takes longer for it to reach our sensors. Everything's about airflow,” he says.

Vape detectors can strain student-teacher relationships

The American Civil Liberties Union, which opposes invasive student searches and seizure of student property, such as cellphones, argues that the harm caused by detectors outweighs the benefits.

The ACLU’s New York-based senior policy counsel, Chad Marlow, says surveillance technologies such as vape detectors can undermine “student relationships with the teachers and administrators who we want them to trust.” Instead, schools might be better served by “a hall monitor who has positive interactions with students and can still look out for vaping,” he says.

To be sure, there is a middle ground. On Long Island, New York, the nonprofit Lindenhurst Community Cares Coalition helped raise $39,000 to put 33 detectors in Lindenhurst Middle School. The system went online in June, so there isn’t much data yet.

But Executive Director Lori-Ann Novello says she and the Lindenhurst Union Free School District are in agreement that the detectors are meant as a “screening tool” to help students by educating rather than punishing them.

Parents, it's time to talk to your child about vaping

Novello says initially, it was the students’ idea. “They thought it was ridiculous that students were being suspended,” she says, only to be sent home where they would be free to vape.

The coalition hopes to tap some of Suffolk County’s $8.8 million share of the Juul settlement to expand to other local schools.

“It’s not a gotcha,” says Lindenhurst district Superintendent Vincent Caravana. “It's not a goal to try to catch someone, to suspend them and to make an example out of them.

“We kind of all universally believe and recognize that addiction is a powerful thing and it's a problem, and we want to address that before it becomes even more of a problem.”

• youth vaping
• public schools

• Introduction
• Conclusions
• Article Information

eTable 1. Instagram account validation procedure

eTable 2. Intercoder reliability—Gwet’s AC1 coefficients

eTable 3. Number of parameters, log-likelihood, and Akaike Information Criterion for the negative binomial and Poisson regression models with Instagram content from synthetic nicotine brands

eTable 4. Proportion of posts featuring warning labels by brand

eTable 5. Descriptive results of post engagement

eFigure. Data inclusion criteria for statistical analysis

Data Sharing Statement

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Wu J , Trifiro BM , Ranker LR, et al. Health Warnings on Instagram Advertisements for Synthetic Nicotine E-Cigarettes and Engagement. JAMA Netw Open. 2024;7(9):e2434434. doi:10.1001/jamanetworkopen.2024.34434

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Health Warnings on Instagram Advertisements for Synthetic Nicotine E-Cigarettes and Engagement

• 1 Annenberg School for Communication, University of Pennsylvania, Philadelphia
• 2 College of Communication, Boston University, Boston, Massachusetts
• 3 Department of Community Health Sciences, School of Public Health, Boston University, Boston, Massachusetts
• 4 Department of Computer Science, Boston University, Boston, Massachusetts
• 5 Section of Cardiovascular Medicine, Department of Medicine, Boston Medical Center, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts
• 6 Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts
• 7 American Heart Association Tobacco Regulation and Addiction Center, Dallas, Texas
• 8 Department of Medicine, School of Medicine, Vanderbilt University, Nashville, Tennessee
• 9 Department of Medicine, University of Louisville, Louisville, Kentucky
• 10 Global Health, School of Public Health, Boston University, Boston, Massachusetts
• 11 Department of Health Law, Policy & Management, School of Public Health, Boston University, Boston, Massachusetts
• 12 Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts

Question   Do synthetic nicotine brands adhere to the Food and Drug Administration (FDA) guidelines for tobacco marketing, and how is the presence of a health warning associated with user engagement on Instagram?

Findings   In this cross-sectional study of 2071 Instagram posts for 25 synthetic nicotine brands, only 263 posts (13%) adhered to FDA health warning requirements. Posts advertising flavored products received more likes and comments, and those with health warnings received fewer comments, indicating that compliance with FDA guidelines reduces user engagement.

Meaning   These findings suggest that enforcing FDA-compliant health warnings on social media posts of synthetic nicotine products may reduce youth engagement with tobacco marketing on social media.

Importance   Synthetic nicotine is increasingly used in e-cigarette liquids along with flavors to appeal to youths. Regulatory loopholes have allowed tobacco manufacturers to use social media to target youths.

Objective   To analyze the extent to which synthetic nicotine e-cigarette brands have implemented US Food and Drug Administration (FDA) health warning requirements and to evaluate the association between health warnings and user engagement on Instagram.

Design, Setting, and Participants   In this cross-sectional study, posts from 25 brands were analyzed across a 14-month period (August 2021 to October 2022). A content analysis was paired with Warning Label Multi-Layer Image Identification, a computer vision algorithm designed to detect the presence of health warnings and whether the detected health warning complied with FDA guidelines by (1) appearing on the upper portion of the advertisement and (2) occupying at least 20% of the advertisement’s area. Data analysis was performed from March to June 2024.

Exposure   Synthetic nicotine e-cigarette advertisement on Instagram.

Main Outcomes and Measures   The outcome variables were user engagement (number of likes and comments). Negative binomial regression analyses were used to evaluate the association between the presence and characteristics of health warnings and user engagement.

Results   Of a total of 2071 posts, only 263 (13%) complied with both FDA health warning requirements. Among 924 posts with health warnings, 732 (79%) displayed warnings in the upper image portion, and 270 (29%) had a warning covering at least 20% of the pixel area. Posts with warnings received fewer comments than posts without warnings (mean [SD], 1.8 [2.5] vs 5.4 [11.7] comments; adjusted incident rate ratio [aIRR], 0.70; 95% CI, 0.57-0.86; P  < .001). For posts containing warnings, a larger percentage of the warning label’s pixel area was associated with fewer comments (aIRR, 0.96; 95% CI, 0.93-0.99; P  = .003). Flavored posts with health warnings placed in the upper image portion received more likes than posts with warnings in the lower portion (mean [SD], 34.6 [35.2] vs 19.9 [19.2] likes; aIRR, 1.48; 95% CI, 1.07-2.06; P  = .02).

Conclusions and Relevance   In this cross-sectional study of synthetic nicotine brand Instagram accounts, 87% of sampled posts did not adhere to FDA health warning requirements in tobacco promotions. Enforcement of FDA compliant health warnings on social media may reduce youth engagement with tobacco marketing.

Synthetic nicotine products have rapidly grown in popularity since their introduction in 2020 and currently account for nearly two-thirds of all product offerings in vape shops across the US. 1 Synthetic nicotine is a form of nicotine produced in a laboratory setting that uses chemical precursors derived from nontobacco sources. 2 Very little is known regarding the health effects associated with synthetic nicotine use. 2 However, synthetic nicotine is pharmacologically similar to tobacco-derived nicotine and likely has similar addictive properties. 2 Nicotine addiction adversely affects brain development and psychosocial health in youths, and those who use e-cigarettes are at increased risk of using combustible tobacco, which has known adverse health outcomes. 3 - 6

Because synthetic nicotine is not derived from tobacco, it evaded the regulatory authority of the US Food and Drug Administration (FDA) until April 2022. 7 This regulatory loophole allowed manufacturers to flood the tobacco market with synthetic nicotine products. 8 Youths who use tobacco are drawn to flavored e-cigarettes. 9 Flavors like pink lemonade and cotton candy, previously banned in traditional tobacco products and cartridge-based e-cigarettes, contribute to the appeal of synthetic nicotine e-cigarettes among youths. 8 , 10 , 11 In addition, manufacturers of synthetic nicotine e-cigarettes often market their products as nontobacco nicotine or tobacco-free nicotine , implying that synthetic nicotine products are safer than traditional tobacco products. 8 , 12 This marketing strategy leads young adults to perceive synthetic nicotine products as less addictive than traditional tobacco products, fostering positive perceptions and potentially increasing trial among youths. 13

Many manufacturers of synthetic nicotine products use social media marketing techniques on platforms such as Instagram, including the use of colorful graphics to emphasize fruit or dessert flavors. 14 Exposure to tobacco advertising on social media is associated with a greater willingness and intention to use e-cigarettes, lower perceived danger of e-cigarette use, and increased tobacco use. 15 - 17 In addition, engagement with content, including liking or following content shared by e-cigarette brands, is associated with e-cigarette trial among youths. 18

Although federal laws require health warning statements to be displayed on the packaging and print advertising for tobacco products sold or distributed in the US, 19 the current standards were developed for a pre–social media world. 20 The gray areas surrounding federal regulation specific to social media marketing of tobacco products are particularly concerning because more than 9 in 10 teens report using the internet at least daily, with approximately one-half of US teens using Instagram daily. 21

Our objective was to analyze the promotional content shared by synthetic nicotine brands on Instagram. We focus on Instagram because it is considered a primary source of socialization and information sharing among youths. 22 , 23 Given the increasing use of synthetic nicotine e-cigarettes among youths and the regulatory loophole in social media marketing of tobacco products, 1 , 20 we hypothesize that (1) the majority of promotional content shared by synthetic nicotine brands on Instagram does not adhere to FDA guidelines for health warnings, 19 and (2) Instagram posts with warnings have lower user engagement (ie, numbers of likes and comments) than posts with no warnings.

Our sample was based on the previously identified leading 107 manufacturers of synthetic nicotine products. 8 To be included in the sample, the synthetic nicotine brand account must (1) have been actively posting on Instagram during the data collection period, and (2) have shared at least 1 post promoting synthetic nicotine products during the study period. We identified 25 synthetic nicotine brand accounts that fit these criteria. We analyzed 2120 posts shared over a 14-month period (August 2021 to October 2022). For carousel posts with multiple images, only the first image was analyzed. The Boston University institutional review board deemed the study to not pertain to human participants; thus, our work was exempt from review and the need for informed consent, in accordance with 45 CFR §46. We followed the Strengthening the Reporting of Observational Studies in Epidemiology ( STROBE ) reporting guidelines. 24

To verify the ownership of the identified synthetic nicotine brand Instagram profiles, we checked whether the profile pictures matched or were similar to the manufacturer’s branding logo on their official websites. In our sample, 76% of the synthetic nicotine brands provided a direct link from their webpage to their Instagram account. We compared each brand’s logo with their Instagram profile picture and determined whether the brand’s webpage linked to an Instagram account (eTable 1 in Supplement 1 ). We also collected data on the Instagram profiles’ features, such as whether there were any age restrictions to view the account, the presence of health warning statements in the account’s profile information, and whether the account self-identified as a business or a personal account.

We manually downloaded 2184 images and videos from 2120 posts, along with their accompanying comments, over a 3-week period in October 2022. We excluded 64 images that were not the first image in a carousel post. Individual posts that hid like counts were excluded from our analysis (38 posts). Engagement metrics for each post (number of likes and comments) were recorded. In line with previous research criteria that exclude posts without sufficient time for engagement, 25 , 26 6 posts were excluded from the sample because they were posted within 48 hours of data collection.

Instagram allows users to differentiate their accounts as business or nonbusiness within the account’s profile. Business accounts have access to enhanced metrics and capabilities compared with nonbusiness accounts, including insights and growth analytics. 27 Our sample of accounts includes 13 designated as business and 12 designated as nonbusiness.

We coded for product flavors, use of fruit or dessert images, and vaping cues. A post featured a vaping cue if it included (1) an individual holding a product (e-cigarette or e-liquid), (2) a vape cloud, and/or (3) actual vaping behavior. Four trained coders (not coauthors of this article) completed 4 rounds of pilot coding for intercoder reliability, achieving a mean Gwet agreement coefficient of 0.94, indicating very good reliability. 28 , 29 The coders then independently coded the remaining posts after establishing reliability. A list of Gwet agreement coefficient intercoder reliability coefficients appear in eTable 2 in Supplement 1 . Upon establishing intercoder reliability, the coders independently coded the remaining posts.

We designed the Warning Label Multi-Layer Image Identification (WaLi) computer vision algorithm 30 to detect the presence of health warnings and whether the health warning label (1) appeared on the upper portion of the advertisement within the trim area and (2) occupied at least 20% of the advertisement’s area, per FDA guidelines for print advertisements of tobacco products. 31 For video posts, we took still images of the first frame of all the videos in the sample to pass through WaLi. We manually validated WaLi on all collected 2184 images, 969 of which had warnings and 1215 that did not. The overall accuracy of WaLi to detect the presence of health warnings in our dataset was 99%, with recall of 98%, precision of 100%, F1 score of 99%, and Hamming Loss of 1.2%.

Data analysis was performed from March to June 2024. Because our outcome variables (likes and comments) are count data, we considered Poisson or negative binomial regressions. Poisson regression assumes the variance equals the mean (ie, no overdispersion), whereas negative binomial regression accommodates overdispersion. 32 Likelihood ratio tests between the Poisson and negative binomial models indicated that negative binomial regression fit the data better (eTable 3 in Supplement 1 ).

Thus, we used negative binomial regression models to examine the association between the presence and characteristics of warnings and user engagement, with separate models for likes and comments. First, for all posts, we analyzed the associations of warning and flavor presence with engagement. Next, for posts promoting flavored synthetic nicotine products specifically, we examined the association of health warning presence with engagement. Then, among posts that included health warnings, we examined how warning placement (whether the warning is placed in the upper portion of the image) and warning size (percentage of pixels covered) were associated with engagement, alongside the presence of flavor. Finally, in posts advertising flavored products with health warnings, we analyzed the association between engagement and warning characteristics (placement and size). Five posts were excluded from the statistical analysis because WaLi was unable to estimate the warning area owing to black borders blending with other black pixels in the images (eFigure in Supplement 1 ).

All models were adjusted for follower counts, days since posting, and whether the content originated from a business account. 33 - 35 We used random effects by brand to account for clustering of the post data within the same brand. Negative binomial models were fit using the glmmADMB package in R statistical software version 4.1.2 (R Project for Statistical Computing). The exponentiated regression coefficients in the negative binomial model are reported as adjusted incident rate ratios (aIRRs). Corresponding 95% CIs and P values are reported, with a 2-sided threshold of P  < .05 for statistical significance.

Table 1 presents an overview of the characteristics of synthetic nicotine e-cigarette brands in the sample. Notably, 13 accounts (52%) restricted access to users younger than 21 years, and 13 accounts were classified as business accounts. In addition, 24 accounts (96%) used a brand logo that was consistent with the profile picture. Only 4 accounts (16%) featured health warnings in their profiles. Age restrictions were noted in the profiles of 14 accounts (56%), and 18 accounts (72%) included links to the manufacturer’s website.

Characteristics of the content shared by synthetic nicotine brand Instagram accounts are shown in Table 2 . Overall, 1523 posts (74%) promoted a flavored product, of which 1326 (64%) promoted a product marketed as clove, spice, candy, fruit, chocolate, alcohol, or other sweet flavors. Nearly 11% of posts (222 posts) promoted a concept flavor, such as pink or cotton fluff, whereas 6% of posts (118 posts) promoted a mint or menthol flavored product. The majority of posts (1486 posts [72%]) did not feature people and 431 posts (21%) featured 1 or more vaping cues.

The proportion of posts featuring health warnings by brand is available in eTable 4 in Supplement 1 . Among posts in our sample, 45% (924 posts) were determined via WaLi to have a health warning. Among posts where a warning was detected, the health warning was in the upper portion of the image for 79% of posts (732 posts), and 29% of posts (270 posts) had a health warning that occupied at least 20% of the pixel area. Only 13% of posts from our entire sample (263 posts) met both FDA guidelines for health warnings.

Across all 2071 posts from 25 brands, the mean (SD) like count was 46.8 (82.0), and the mean (SD) comment count was 3.8 (9.1). eTable 5 in Supplement 1 contains the descriptive results of post engagement across the analyzed samples. In negative binomial models adjusted for follower counts, business status, and days on Instagram, posts with health warnings received fewer comments than posts without health warnings (mean [SD], 1.8 [2.5] vs 5.4 [11.7] comments; aIRR, 0.70; 95% CI, 0.57-0.86; P  < .001). Posts advertising flavored products received more likes (aIRR, 1.12; 95% CI, 1.04-1.21; P  = .002) and comments (aIRR, 1.16; 95% CI, 1.04-1.30; P  = .008) than posts without a flavored product. The presence of a health warning was not associated with the number of likes a post received (aIRR, 0.95; 95% CI, 0.83-1.08; P  = .42) ( Table 3 ).

Among 924 posts with health warnings, a greater proportion of the warning label’s pixel area was associated with fewer comments (aIRR, 0.96; 95% CI, 0.93-0.99; P  = .003), with no significant association found for likes (aIRR, 0.99; 95% CI, 0.98-1.003; P  = .13). A health warning in the upper portion of the post’s image was not associated with numbers of likes (aIRR, 1.28; 95% CI, 0.96-1.70; P  = .09) or comments (aIRR, 1.50; 95% CI, 0.87-2.58; P  = .15) ( Table 4 ).

Among 1523 posts that advertised flavored synthetic nicotine products, the presence of a health warning was associated with fewer comments (aIRR, 0.71; 95% CI, 0.57-0.88; P  = .002) but not associated with likes (aIRR, 0.96; 95% CI, 0.83-1.12; P  = .64) ( Table 3 ). When focusing on 851 posts promoting flavored products with health warnings, a higher percentage of the warning label’s pixel area was associated with fewer comments (aIRR, 0.96; 95% CI, 0.93-0.99; P  = .003). A health warning in the upper portion of the post’s image was associated with increased numbers of likes (mean [SD], 34.6 [35.2] vs 19.9 [19.2] likes; aIRR, 1.48; 95% CI, 1.07-2.06; P  = .02) ( Table 4 ).

This cross-sectional study found that most synthetic nicotine brand Instagram posts (87%) do not adhere to FDA health warning requirements for tobacco advertising. Our findings show an association between the presence of a health warning and user engagement on Instagram. Posts that feature health warnings received fewer comments. Warnings covering a larger percentage of the pixel area received fewer comments.

Although there are not yet social media–specific guidelines for tobacco marketing, our findings suggest that the implementation of FDA guidelines for warning labels in promotional content for synthetic nicotine products negatively affects social media engagement. Larger warning sizes in particular are associated with reduced post engagement.

Although our study did not find an association between the presence of a health warning and number of likes, our work shows a clear association between health warnings and comments. Although it is easy to like a post, a user needs to exert more effort to comment on a post, suggesting more engagement. 36

Consistent with prior research demonstrating the appeal of flavors in e-cigarettes to youths, 14 , 37 - 41 our study found that synthetic nicotine brands on Instagram frequently promote fruit and dessert flavors, which were associated with higher likes and comments. A majority (74%) of posts featured flavored products, often showcased with visually appealing images of fruits or desserts. Our findings reveal that FDA-compliant health warnings were negatively associated with comments on posts promoting flavored synthetic nicotine products, suggesting that health warnings may effectively reduce engagement with such promotional content of synthetic nicotine e-cigarettes.

Unexpectedly, placing a health warning in the upper portion of posts promoting flavored products was associated with increased likes. One possible explanation is that when warnings are not displayed in the upper portion of the post, they are likely to be placed on the product in the post. Warnings on products may lead people to directly associate nicotine’s health risks with the product, possibly resulting in fewer likes for the post. Therefore, more research is necessary to explore how placing warnings in social media marketing of synthetic nicotine products (eg, on the products) influences user engagement and perceptions of synthetic nicotine e-cigarettes.

Research 42 - 45 shows that vaping in advertisements for e-cigarettes can serve as a cue to individuals who use tobacco products, increasing the urge to vape and smoke combustible cigarettes. Exposure to vaping cues has been associated with lower levels of intention to quit or abstain from tobacco use. 42 - 45 Although the majority of posts did not feature people, of those that did, models were often engaged in vaping cues. This finding shows how synthetic nicotine brands model vaping behavior for social media audiences.

Current federal regulations mandate health warnings on print and image-based advertisements for tobacco products, but it remains unclear whether these regulations apply to all forms of social media marketing. Similar to prior research, 31 our study indicates that including health warnings is associated with reduced social media engagement with social media tobacco promotions. The use of health warnings can convey the risks associated with tobacco products to social media users, which may ultimately deter uptake and use of tobacco products. 46 - 48 Given the link between exposure to e-cigarette marketing on social media and youth tobacco initiation, 16 , 49 - 52 our findings suggest that clarifying regulations for implementing health warnings in promotional content for synthetic nicotine products on social media may deter engagement with such brand content.

This study has limitations that should be acknowledged. We relied on data acquired from a social media platform, which may introduce inherent biases. To mitigate this challenge, we conducted a thorough search for synthetic nicotine brands to ensure diverse and representative samples. We also used objective machine learning methods to measure the presence and properties of health warnings. Our findings may not be generalizable to other tobacco products, brands, or social media platforms. In addition, our study only analyzed engagement metrics including likes and comments. Future research should further explore the sentiment of comments to better understand how health warnings affect audience perceptions of brands and products. We do not know the tobacco use status of the Instagram users who engaged with the posts in our sample, nor do we know the ages of users exposed to these posts; therefore, we cannot determine or argue any causal effects of the presence of health warnings on user outcomes, such as tobacco use or intention to quit.

Our study did not analyze the exact language used in health warnings. The language used in the sampled warnings varied among brands. Future research would benefit from analyzing specific language used in health warnings to understand how brands are conveying potential harms associated with using tobacco products. Because WaLi relies on a modular algorithm, future research could benefit from adapting the Optical Character Recognition model language in order to identify warnings in different languages. In addition, the time period of our data collection falls before and after the regulatory shift in April 2022 that brought synthetic nicotine under the FDA’s regulatory purview. Although our study does not analyze how posting behavior of synthetic nicotine brands changed during this time period because it is outside the scope of our project, future work would benefit from a comprehensive understanding of whether this regulatory shift led to changes in the social media strategies of synthetic nicotine brands.

In the current study, most promotional Instagram content posted by synthetic nicotine brands did not adhere to federal regulations requiring health warnings on advertisements. Posts that included health warnings and a larger warning size received less user engagement. Health warnings may lessen user engagement, which could deter youth uptake and use of synthetic nicotine products.

Accepted for Publication: July 24, 2024.

Published: September 13, 2024. doi:10.1001/jamanetworkopen.2024.34434

Open Access: This is an open access article distributed under the terms of the CC-BY License . © 2024 Wu J et al. JAMA Network Open .

Corresponding Author: Traci Hong, PhD, College of Communication, Boston University, 640 Commonwealth Ave, Boston, MA 02215 ( [email protected] ).

Author Contributions: Dr Wu and Ms Trifiro had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Dr Wu, Ms Trifiro, Dr Fetterman, and Dr Hong contributed equally to this work.

Concept and design: Wu, Ranker, Origgi, Benjamin, Robertson, Bhatnagar, Cornacchione Ross, Fetterman, Hong.

Acquisition, analysis, or interpretation of data: Wu, Trifiro, Ranker, Origgi, Stokes, Xuan, Wijaya, Plummer, Cornacchione Ross, Fetterman, Hong.

Drafting of the manuscript: Trifiro, Origgi, Wijaya, Fetterman, Hong.

Critical review of the manuscript for important intellectual content: Wu, Ranker, Benjamin, Robertson, Bhatnagar, Stokes, Xuan, Plummer, Cornacchione Ross, Fetterman, Hong.

Statistical analysis: Wu, Ranker, Origgi, Hong.

Obtained funding: Robertson, Fetterman, Hong.

Administrative, technical, or material support: Stokes, Wijaya, Plummer, Cornacchione Ross, Fetterman, Hong.

Supervision: Bhatnagar, Cornacchione Ross, Fetterman, Hong.

Conflict of Interest Disclosures: None reported.

Funding/Support: Research reported in this publication was supported, in part, by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) under Award Number U54HL120163 (support to Drs Ranker, Robertson, and Fetterman). Ms Trifiro and Dr Ranker were supported by grants from the American Heart Association. Dr Fetterman was supported by NHLBI grant K01 HL143142. Dr Benjamin was supported by NIH grant R01HL092577 and American Heart Association grant AHA18SFRN34110082.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, the Food and Drug Administration, or the American Heart Association.

Meeting Presentation: Preliminary results of this research were presented at the annual meeting for Society for Research on Nicotine and Tobacco; March 3, 2023; San Antonio, Texas.

Data Sharing Statement: See Supplement 2 .

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What is new in electronic-cigarettes research?

Brian p. jenssen.

a Department of Pediatrics, University of Pennsylvania School of Medicine and PolicyLab and the Center for Pediatric Clinical Effectiveness, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania

Karen M. Wilson

b Department of Pediatrics, Icahn School of Medicine at Mount Sinai, New York City, New York, USA

Purpose of review

Electronic cigarettes (e-cigarettes) and other vaping devices have seen extraordinary growth in use in the past 10 years, and companies are accelerating their development of new products and marketing efforts. In turn, researchers have increased their efforts to determine how e-cigarettes affect health, how marketing these products impacts adolescents and how the use of e-cigarettes may affect adolescents’ use of other tobacco products. Products like Juul were not on the market 2 years ago; thus, frequent updates on the topic are essential.

Recent findings

Studies have begun to demonstrate that users of the newer pod systems are exposed to high levels of nicotine, as well as other chemicals. These products are highly marketed, with a strong emphasis on how adolescents can use them surreptitiously. This is concerning to researchers, and other studies have continued to demonstrate that teens who use e-cigarettes are more likely to go on to use combusted tobacco. Further research has also failed to demonstrate that e-cigarettes are useful for people wishing to quit smoking combusted tobacco.

E-cigarettes and vaping systems are not safe products and should not be used by adolescents.

EMERGING ELECTRONIC CIGARETTE PRODUCTS

Electronic cigarettes (e-cigarettes), in general, use an electric impulse to heat a nicotine containing liquid to the point where it aerosolizes but does not burn. The use of e-cigarettes is called ‘Vaping’. It is promoted by the industry as an alternative to smoking; however, studies have not shown that they are effective for smoking cessation. The industry has long used marketing techniques that are appealing to adolescents and young adults, such as cartoons and hyper-sexual imagery. These products are also marketed in a variety of flavors, which are far more appealing to youth than a tobacco-flavored product. The industry has been rapidly innovative, from the cigarette-like products introduced in the early 2000s ( Fig. 1 ) to the ‘mods’ or modified tank systems ( Fig. 2 ) [ 1 ]. Recently, the industry has developed e-cigarette products that are more technologically advanced. These products are designed to look like electronic devices, car fobs, coffee cups, credit cards, mobile phones or even tic-tac boxes [ 2 ]. Quite distressing to pediatricians are the vaping devices designed to look like asthma inhalers; versions are used to aerosolize marijuana leaf (PUFFiT), or nicotine (QuickNIC). Companies have also developed low vapor and low odor products specifically to facilitate public use.

First generation e-cigarette.

Tank system or ‘Mod’.

The JUUL e-cigarette ( Fig. 3 ) was introduced in 2015; by 2016, reports were emerging about its prevalence of use among adolescents. JUUL pods contain 59 mg/ml of nicotine, which is a significantly higher concentration than the standard e-cigarette liquid. A study completed in June 2018 found 148000 videos on YouTube when searching on ‘JUUL’ [ 2 ], including 15 000 from ‘JUUL at school’, 1040 from ‘JUUL in school bathroom’ and 6840 from ‘JUUL in class’. A variety of suggested techniques for hiding the aerosol plume includes inhaling more deeply (and increasing nicotine absorption), swallowing the aerosol, exhaling under clothing or into a napkin or paper towel. The study also found YouTube videos detailing how to hide JUUL pods. One video demonstrated the use of a Sharpie marker ( Fig. 4 ) [ 2 ].

JUUL with pods. Permission: Susanne Tanski, MD, MPH.

Hiding JUUL in a Sharpie. Source: Ramamurthy et al. [ 2 ].

A recent study evaluated the exposure to nicotine by adolescents who used JUUL and other vape pod systems, using urine samples and teen-reported use of e-cigarettes [ 3■ ]. In this sample of 506 teens, ages 12–21 years, 7.7% were daily pod users; JUUL was the most popular brand (80%). Bo (36%), Phix (18%) and Suorin (12%) were also popular. The preferred flavors were menthol/mint (24%), fruit (21%) and candy/desserts (18%). The median urinary cotinine of exclusive pod users ( N = 22) in this study was 244.8 ng/ml – an amount higher than has been reported in studies of exclusive combusted tobacco users [ 4 ]. Urinary cotinine varied by the type of pod used: the median urinary cotinine of exclusive JUUL users was 135 ng/ml, compared with 508 ng/ml for exclusive Bo users and 906 ng/ml for exclusive Phix users. This study highlights the high levels of nicotine that adolescents are exposed to when they use these vape pod systems.

ADOLESCENT EXPOSURE TO TOXIC CHEMICALS FROM ELECTRONIC-CIGARETTES

E-cigarettes are promoted as a ‘reduced harm’ product that leads to far less exposure to toxic chemicals than with combusted cigarettes. However, few studies have examined the actual exposures e-ciga-rette users have. In another study, 67 e-cigarette-only users were evaluated and compared to dual users (N=16) and nontobacco using controls ( N = 20). In comparison to the above study, these e-cigarette-only users had a wide range of urinary cotinine levels (0–864 ng/ml), with a median of 0, suggesting that many users were not exposed to the same degree of nicotine. Further, the study team found that the e-cigarette-only users, compared with controls, had higher levels of the volatile organic compounds (VOCs) acrylonitrile (1.3 vs. Ong/mg), acrolein (254 vs. 193ng/mg), propylene oxide (29 vs. 14ng/mg), acrylamide (67 vs. 42 ng/mg) and crotonaldehyde (149 vs. 130ng/mg) [ 5■ ]. Fruit flavor use was also associated with increased levels of acrylonitrile (10 vs. 2ng/mg). Adolescents who used both tobacco and e-cigarettes had VOC levels up to three times higher than those who used only e-cigarettes. This suggests that even in the absence of high nicotine levels in these products, users are exposed to toxic chemicals – chemicals identified as carcinogenic – created by the vaping of the humectant or flavors. Adolescents should never use e-cigarette or vaping products.

ELECTRONIC-CIGARETTE USE AMONG YOUTH AND PROGRESSION TO TRADITIONAL CIGARETTE USE

In January 2018, the National Academies of Sciences, Engineering, and Medicine (NASEM, formerly known as the Institute of Medicine), with support from the Center for Tobacco Products of the Food and Drug Administration (FDA), published an expert committee report of the scientific evidence about e-cigarettes and public health. The report, titled the Public Health Consequences of E-Cigarettes, provides both an overview and in-depth analysis of the evidence, recommends ways to improve the research and highlights gaps that are priority focus areas for future work [ 6 ].

For youth and young adults, there is substantial evidence that e-cigarette use increases the risk of ever using combustible tobacco cigarettes [ 6 , 7 ]. Further, for e-cigarette users who have also ever used combustible tobacco cigarettes, there is moderate evidence that e-cigarette use increases the frequency and intensity of subsequent combustible tobacco cigarette smoking [ 6 ]. These conclusions are based on substantial evidence from several separate, well-designed, longitudinal studies [ 8 – 15 ]. Adolescents and young adults (aged 14–30) who have used e-cigarettes are 3.6 times more likely to report using cigarettes at follow-up, compared to those who had not, according to a recent meta-analysis [ 7 ]. In addition, adolescents who use e-cigarettes appear to have fewer social and behavioral risk factors than conventional cigarette users [ 10 – 12 , 14 ].

These findings raise significant concern that e-cigarettes have the potential to addict a new generation to nicotine and tobacco, slowing or reversing the decline in adolescent cigarette smoking that has occurred over the past 20 years. Data have begun to influence policy, with the FDA recently acknowledging adolescent e-cigarette use as an epidemic. ‘E-cigs have become an almost ubiquitous — and dangerous — trend among teens,’ FDA Commissioner Scott Gottlieb, M.D., said in a statement in September 2018. ‘The disturbing and accelerating trajectory of use we’re seeing in youth, and the resulting path to addiction, must end’ [ 16 ].

ELECTRONIC-CIGARETTES FOR SMOKING CESSATION FOR ESTABLISHED SMOKERS

Health claims that e-cigarettes are effective smoking cessation aids are not currently supported by scientific evidence. According to the NASEM report, there is limited evidence regarding the ability of e-cigarettes to promote smoking cessation [ 6 ]. In particular, with a limited number of small, randomized controlled trials, there is insufficient evidence on the effectiveness of e-cigarettes as cessation aids compared with no treatment or to FDA-approved smoking cessation treatments [ 6 ]. A more recent large-scale, randomized controlled trial found that the use of free e-cigarettes does not result in higher rates of sustained abstinence than traditional smoking-cessation aids and does not increase abstinence rates among smokers who are also offered information and motivational text messages [ 17 ].

The overall evidence from observational trials is mixed [ 6 ]. When compared to randomize controlled trials, it is inherently more difficult to draw conclusions about the relationship between cause and effect because of the potential for selection bias and unmeasured confounding. Two systematic reviews that included cohort studies published between 2013 and 2015 in meta-analyses each found a negative association between e-cigarette use and cessation, meaning e-cigarette users have lower rates of successful quitting compared to never e-cigarette users [ 18 , 19 ]. The NASEM report identified that more recent prospective longitudinal studies report that daily or very frequent e-cigarette use may be associated with cessation, whereas intermittent use may not [ 6 ]. Given the current state of the science, smokers interested in quitting should seek and be referred to evidence-based, safe and effective treatments, including nicotine replacement therapy, behavioral counseling and additional pharmacotherapy [ 20 ].

For established smokers, e-cigarettes may reduce health risks for the individual user compared to the risk of continued combustible tobacco use [ 6 ]. However, tobacco, when used as intended, causes disease, disability and death [ 21 ], and discussions and messaging about individual tobacco products must placed in a larger public health context. Even if e-cigarettes themselves pose less risk to the user than other tobacco products, they still represent a significant public health burden in need of further regulation, particularly if they cause more adolescents and adults to begin harmful combustible tobacco use or prevent fewer people from quitting tobacco use [ 6 ].

AREAS FOR FURTHER RESEARCH

The NASEM report closed with a call for action: ‘More and better research is needed to help clarify whether e-cigarettes will prove to reduce harm—or induce harm—at the individual and the population levels.’[ 6 ] As the e-cigarette market grows, there is continued need for research to inform regulatory standards and understand the effects of use and exposure across the lifespan [ 6 ]. Additional research is needed to understand the trajectory of addiction among youth and the progression to combustible tobacco products [ 22 ]. Studies are needed to determine whether and, if so, how e-cigarettes may be effective for smoking cessation [ 6 ]. Finally, research is needed to evaluate effective counter-messaging and public health interventions, especially regarding preventing adolescent e-cigarette initiation.

New research in 2018 is strongly pointing to the potential for e-cigarette products to exposure their users to toxic chemicals, the likelihood of addicting adolescents to nicotine and possible future combusted tobacco use and the continued failure of rigorous studies to show that these products are effective for smoking cessation. The FDA has delayed the implementation of tighter regulations on e-cigarette products, but this year has recognized the dangers of adolescent exposure and targeted companies such as JUUL for their appeal to teens. Pediatricians and other healthcare practitioners that provide care to young adults and adolescents should continue to stress the dangers of using these products to patients and their parents as well as advocate for restrictions on the purchase and use of these products by teens.

• Recent evidence highlights the high levels of nicotine that adolescents are exposed to when they use vape pod system e-cigarettes, such as JUUL.
• Even in the absence of high nicotine levels in these products, users are exposed to toxic chemicals – chemicals identified as carcinogenic – created by the vaping of the humectant or flavors.
• For youth and young adults, there is substantial evidence that e-cigarette use increases the risk of ever using combustible tobacco cigarettes.
• According to the National Academy of Science report on the public health consequences of e-cigarettes, there is limited evidence regarding the ability of e-cigarettes to promote smoking cessation.
• Pediatricians and other healthcare practitioners that provide care to young adults and adolescents should continue to stress the dangers of using these products to patients and their parents as well as advocate for restrictions on the purchase and use of these products by teens.

Acknowledgements

Financial support and sponsorship

Solicited Review.

We confirm that our article has not been published in its current form or a substantially similar form (in print or electronically; including on a website), that it has not been accepted for publication elsewhere, and that it is not under consideration by another publication.

Conflicts of interest

There are no conflicts of interest.

REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

■ of special interest

■■ of outstanding interest

Study finds e-cigarette ads on social media often misleading

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Island breeze, blue lagoon, dew drop-;these aren't the names of scented candles on display at your local home goods store. They're flavors of synthetic nicotine used in e-cigarettes, often advertised with neon-electric colors and bright lettering to make them look like boxes of candy or fruit juice. But underneath all the flair, a specific label written clearly in black text on a white background is required by law to be there: a warning that says the product contains nicotine and that nicotine is an addictive substance. 

Even though health warnings need to be written on physical products sold in stores and included in traditional advertisements, a new research study led by Boston University found that the majority of ads posted on social media by synthetic nicotine brands left the warnings off.

Synthetic nicotine is a substance created in a laboratory that has the same, or very similar, chemical structure to the nicotine derived from tobacco leaves. Despite marketing that labels it as "tobacco-free nicotine," it still has the same addictive properties and additives that can cause lung damage, cancer, and other health issues. Plus, since it's commonly paired with appealing flavors-;made from chemicals that are known to be unsafe to inhale-;it can be even harder to quit. 

"When synthetic nicotine started appearing in products, we really wanted to know how it was being received and how it was being promoted," says Traci Hong, a BU College of Communication professor of media studies.

When she first started in her career as a health communication researcher, she says, it was a different era: social media was not widely used, cigarette use was declining, and electronic cigarettes and vapes were in their infancy. But when vapes containing synthetic nicotine started getting more and more popular, she turned her attention to social media to find out how the advertising of these products was being regulated-;and what could be done to make them less appealing to kids and young adults. 

In their new paper, Hong and her collaborators found that in over 2,000 Instagram posts from 25 different synthetic nicotine brands, the vast majority did not include warning labels informing users about the health risks. The findings have been published in JAMA Network Open . 

These are brands that I think have a legitimate responsibility to inform their potential consumers that there are health risks and you need to be aware of them." Traci Hong, Professor, Media Studies, College of Communication, Boston University 

Especially considering that Instagram is one of the most popular social media platforms in the US for young adults. 

The FDA passed a requirement in 2022 that says health warnings need to take up 20 percent of the advertising and appear in the upper portion of the advertisement for e-cigarettes that contain synthetic nicotine. Hong, who is a research fellow at BU's Rafik B. Hariri Institute for Computing and Computational Science & Engineering, and her colleagues identified whether an image posted on Instagram included the required health warning and, if it did, whether it took up the right amount of space. The study involved interdisciplinary collaboration across the University, including experts from BU's School of Public Health, Chobanian & Avedisian School of Medicine, and College of Arts & Sciences. 

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The Instagram posts were analyzed using a custom-built AI algorithm, called Warning Label Multi-Layer Image Identification (WaLi), which uses computer vision to detect if health warnings follow the FDA rules. The team found that only 13 percent of the analyzed posts complied with FDA health warning requirements. They also discovered that the posts with health warnings received fewer likes and comments than posts without the warnings. According to the paper, the larger the warning label, the less comments the posts received. This means that having health warning labels could reduce how many social media users, especially young adults, are seeing and engaging with this content. 

"We need federal government policies to combat the appeal of e-cigarette advertising on social media and to prevent kids from using tobacco products," says Jessica Fetterman, a Chobanian & Avedisian School of Medicine assistant professor of medicine and coauthor on the study. The FDA recently estimated that the number of middle and high school students using e-cigarettes in 2024 is about 1.63 million, down from 2.13 million in 2023, with the vast majority using flavored nicotine. Enforcing and requiring health warning labels on social media content is one way to make products less visible and appealing, Fetterman says. 

"Our study indicates that e-cigarette brands are creating Instagram posts advertising their products with seemingly no enforcement by the social media platform or government," Fetterman says. Instagram lists tobacco products, electronic cigarettes, "and any other products that simulate smoking" on their list of prohibited branded content. But, Fetterman says, synthetic nicotine products are flouting that rule.

"All our work is really trying to find evidence-based research to help people make informed decisions about their health," Hong says. With synthetic nicotine and e-cigarette companies continuing to use flavors as a way to appeal to youth, she says, her team plans to monitor social media posts with WaLi to ensure brands are using the correct language to dissuade people from getting hooked. 

Boston University

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Tags: Cancer , Chemicals , Cigarette , Fruit , Heart , Laboratory , Language , Medicine , Nicotine , Public Health , Research , Smoking , students , Tobacco

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In this interview, discover how Charles River uses the power of microdialysis for drug development as well as CNS therapeutics.

Global and Local Efforts to Take Action Against Hepatitis

Lindsey Hiebert and James Amugsi

In this interview, we explore global and local efforts to combat viral hepatitis with Lindsey Hiebert, Deputy Director of the Coalition for Global Hepatitis Elimination (CGHE), and James Amugsi, a Mandela Washington Fellow and Physician Assistant at Sandema Hospital in Ghana. Together, they provide valuable insights into the challenges, successes, and the importance of partnerships in the fight against hepatitis.

Addressing Important Cardiac Biology Questions with Shotgun Top-Down Proteomics

In this interview conducted at Pittcon 2024, we spoke to Professor John Yates about capturing cardiomyocyte cell-to-cell heterogeneity via shotgun top-down proteomics.

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