difference between literature review and background

Educational resources and simple solutions for your research journey

Key Differences Between the Background of a Study and Literature Review

Don’t be too hard on yourself if you didn’t realize the study background and literature review were two distinct entities. The study background and literature review are both important parts of the research paper; however, due to their striking similarities, they are frequently confused with one another 1 . In this article, we will look at the key differences between the background of a study and literature review and how to write each section effectively.  

When it comes to similarities between the study background and the literature review, both provide information about existing knowledge in a specific field by discussing various studies and developments. They almost always address gaps in the literature to contextualize the study at hand. So, how do they differ from one another? Simple answer: A literature review is an expanded version of the study background, or a study background is a condensed version of a literature review. To put it another way, “a study background is to a literature review what an abstract is to a paper.”  

Differences between the background of the study and a literature review  

Though the distinctions are subtle, understanding them is critical to avoiding confusion between these two elements. The following are the differences between the background of the study and a literature review:  

• The background of a study is discussed at the beginning of the introduction while the literature review begins once the background of a study is completed (in the introduction section).  
• The study background sets the stage for the study; the main goal of the study background is to effectively communicate the need for the study by highlighting the gaps in answering the open-ended questions. In contrast, a literature review is an in-depth examination of the relevant literature in that field in order to prepare readers for the study at hand . Furthermore, the literature review provides a broad overview of the topic to support the case for identifying gaps.  
• The study background and literature review serve slightly different purposes; the study background emphasizes the significance of THE study, whereas the review of literature emphasizes advancement in the field by conducting a critical analysis of existing literature. It should be noted that a literature review also identifies gaps in the literature by comparing and analyzing various studies, but it is the study background that summarizes the critical findings that justifies the need for the research at hand.  
• Another interesting difference is how they are structured; the study background structure follows a top-down approach, beginning with a discussion of a broader area and eventually narrowing down to a specific question—study problem—addressed in the study.   
• The length of the background of the study and the literature review also differ, with the former being more concise and crisp and the latter being more detailed and elaborate.  

Tips to effectively write the background of the study  

Writing the background of the study is sometimes a difficult undertaking for early career researchers; however, because this is an important component of the paper, it is critical that once write it clearly and accurately. The background must convey the context of the study, defining the need to conduct the current study 2 . The study background should be organized in such a way that it provides a historical perspective on the topic, while identifying the gaps that the current study aims to fill. If the topic is multidisciplinary, it should concisely address the relevant studies, laying the groundwork for the research question at hand. To put it simply, the researchers can follow the structure below:  

• What is the state of the literature on the subject?  
• Where are the gaps in the field?  
• What is the importance of filling these gaps?  
• What are the premises of your research?  

The idea is to present the relevant studies to build the context without going into detail about each one; remember to keep it concise and direct. It is recommended that the findings be organized chronologically in order to trace the developments in the field and provide a snapshot of research advancements. The best way is to create an engaging story to pique readers’ interest in the topic by presenting sequential findings that led to YOUR research question. The flow should be such that each study prepares for the next while remaining in accordance with the central theme. However, the author should avoid common blunders such as inappropriate length (too long or too short), ambiguity, an unfocused theme, and disorganization.  

Tips to write the literature review without mixing it up with the background of the study  

As previously discussed in this article, the literature review is an extended version of the background of the study. It follows the background of the study and presents a detailed analysis of existing literature to support the background.   

Authors must conduct a thorough research survey that includes various studies related to the broad topics of their research. Following an introduction to a broader topic, the literature review directs readers to relevant studies that are significant for the objectives of the present study.   

The authors are advised to present the information thematically, preferably chronologically, for a better understanding of the readers from a wide range of disciplines. This arrangement provides a more complete picture of previous research, current focus, and future directions. Finally, there are two types of literature reviews that serve different purposes in papers; they are broadly classified as experimental and theoretical literature reviews. This, however, is a topic for another article.  

We believe you can now easily distinguish between the study background and the literature review and understand how you can write them most effectively for your next study. Have fun writing!  

  References  

• Qureshi, F. 6 Differences between Study Background and Literature Review. Editage Insights, May 3, 2019. https://www.editage.com/insights/6-differences-between-a-study-background-and-a-literature-review .  
• Sachdev, R. How to Write the Background of Your Study. Editage Insights, November 27, 2018. https://www.editage.com/insights/how-to-write-the-background-of-your-study .  

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What Is A Literature Review?

A plain-language explainer (with examples).

By:  Derek Jansen (MBA) & Kerryn Warren (PhD) | June 2020 (Updated May 2023)

If you’re faced with writing a dissertation or thesis, chances are you’ve encountered the term “literature review” . If you’re on this page, you’re probably not 100% what the literature review is all about. The good news is that you’ve come to the right place.

Literature Review 101

• What (exactly) is a literature review
• What’s the purpose of the literature review chapter
• How to find high-quality resources
• How to structure your literature review chapter
• Example of an actual literature review

What is a literature review?

The word “literature review” can refer to two related things that are part of the broader literature review process. The first is the task of  reviewing the literature  – i.e. sourcing and reading through the existing research relating to your research topic. The second is the  actual chapter  that you write up in your dissertation, thesis or research project. Let’s look at each of them:

Reviewing the literature

The first step of any literature review is to hunt down and  read through the existing research  that’s relevant to your research topic. To do this, you’ll use a combination of tools (we’ll discuss some of these later) to find journal articles, books, ebooks, research reports, dissertations, theses and any other credible sources of information that relate to your topic. You’ll then  summarise and catalogue these  for easy reference when you write up your literature review chapter. 

The literature review chapter

The second step of the literature review is to write the actual literature review chapter (this is usually the second chapter in a typical dissertation or thesis structure ). At the simplest level, the literature review chapter is an  overview of the key literature  that’s relevant to your research topic. This chapter should provide a smooth-flowing discussion of what research has already been done, what is known, what is unknown and what is contested in relation to your research topic. So, you can think of it as an  integrated review of the state of knowledge  around your research topic. 

What’s the purpose of a literature review?

The literature review chapter has a few important functions within your dissertation, thesis or research project. Let’s take a look at these:

Purpose #1 – Demonstrate your topic knowledge

The first function of the literature review chapter is, quite simply, to show the reader (or marker) that you  know what you’re talking about . In other words, a good literature review chapter demonstrates that you’ve read the relevant existing research and understand what’s going on – who’s said what, what’s agreed upon, disagreed upon and so on. This needs to be  more than just a summary  of who said what – it needs to integrate the existing research to  show how it all fits together  and what’s missing (which leads us to purpose #2, next). 

Purpose #2 – Reveal the research gap that you’ll fill

The second function of the literature review chapter is to  show what’s currently missing  from the existing research, to lay the foundation for your own research topic. In other words, your literature review chapter needs to show that there are currently “missing pieces” in terms of the bigger puzzle, and that  your study will fill one of those research gaps . By doing this, you are showing that your research topic is original and will help contribute to the body of knowledge. In other words, the literature review helps justify your research topic.  

Purpose #3 – Lay the foundation for your conceptual framework

The third function of the literature review is to form the  basis for a conceptual framework . Not every research topic will necessarily have a conceptual framework, but if your topic does require one, it needs to be rooted in your literature review. 

For example, let’s say your research aims to identify the drivers of a certain outcome – the factors which contribute to burnout in office workers. In this case, you’d likely develop a conceptual framework which details the potential factors (e.g. long hours, excessive stress, etc), as well as the outcome (burnout). Those factors would need to emerge from the literature review chapter – they can’t just come from your gut! 

So, in this case, the literature review chapter would uncover each of the potential factors (based on previous studies about burnout), which would then be modelled into a framework. 

Purpose #4 – To inform your methodology

The fourth function of the literature review is to  inform the choice of methodology  for your own research. As we’ve  discussed on the Grad Coach blog , your choice of methodology will be heavily influenced by your research aims, objectives and questions . Given that you’ll be reviewing studies covering a topic close to yours, it makes sense that you could learn a lot from their (well-considered) methodologies.

So, when you’re reviewing the literature, you’ll need to  pay close attention to the research design , methodology and methods used in similar studies, and use these to inform your methodology. Quite often, you’ll be able to  “borrow” from previous studies . This is especially true for quantitative studies , as you can use previously tried and tested measures and scales. 

How do I find articles for my literature review?

Finding quality journal articles is essential to crafting a rock-solid literature review. As you probably already know, not all research is created equally, and so you need to make sure that your literature review is  built on credible research . 

We could write an entire post on how to find quality literature (actually, we have ), but a good starting point is Google Scholar . Google Scholar is essentially the academic equivalent of Google, using Google’s powerful search capabilities to find relevant journal articles and reports. It certainly doesn’t cover every possible resource, but it’s a very useful way to get started on your literature review journey, as it will very quickly give you a good indication of what the  most popular pieces of research  are in your field.

One downside of Google Scholar is that it’s merely a search engine – that is, it lists the articles, but oftentimes  it doesn’t host the articles . So you’ll often hit a paywall when clicking through to journal websites. 

Thankfully, your university should provide you with access to their library, so you can find the article titles using Google Scholar and then search for them by name in your university’s online library. Your university may also provide you with access to  ResearchGate , which is another great source for existing research. 

Remember, the correct search keywords will be super important to get the right information from the start. So, pay close attention to the keywords used in the journal articles you read and use those keywords to search for more articles. If you can’t find a spoon in the kitchen, you haven’t looked in the right drawer. 

Need a helping hand?

How should I structure my literature review?

Unfortunately, there’s no generic universal answer for this one. The structure of your literature review will depend largely on your topic area and your research aims and objectives.

You could potentially structure your literature review chapter according to theme, group, variables , chronologically or per concepts in your field of research. We explain the main approaches to structuring your literature review here . You can also download a copy of our free literature review template to help you establish an initial structure.

In general, it’s also a good idea to start wide (i.e. the big-picture-level) and then narrow down, ending your literature review close to your research questions . However, there’s no universal one “right way” to structure your literature review. The most important thing is not to discuss your sources one after the other like a list – as we touched on earlier, your literature review needs to synthesise the research , not summarise it .

Ultimately, you need to craft your literature review so that it conveys the most important information effectively – it needs to tell a logical story in a digestible way. It’s no use starting off with highly technical terms and then only explaining what these terms mean later. Always assume your reader is not a subject matter expert and hold their hand through a journe y of the literature while keeping the functions of the literature review chapter (which we discussed earlier) front of mind.

Example of a literature review

In the video below, we walk you through a high-quality literature review from a dissertation that earned full distinction. This will give you a clearer view of what a strong literature review looks like in practice and hopefully provide some inspiration for your own. 

Wrapping Up

In this post, we’ve (hopefully) answered the question, “ what is a literature review? “. We’ve also considered the purpose and functions of the literature review, as well as how to find literature and how to structure the literature review chapter. If you’re keen to learn more, check out the literature review section of the Grad Coach blog , as well as our detailed video post covering how to write a literature review . 

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

16 Comments

Thanks for this review. It narrates what’s not been taught as tutors are always in a early to finish their classes.

Thanks for the kind words, Becky. Good luck with your literature review 🙂

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This is review is amazing. I benefited from it a lot and hope others visiting this website will benefit too.

Timothy T. Chol [email protected]

Thank you very much for the guiding in literature review I learn and benefited a lot this make my journey smooth I’ll recommend this site to my friends

This was so useful. Thank you so much.

Hi, Concept was explained nicely by both of you. Thanks a lot for sharing it. It will surely help research scholars to start their Research Journey.

The review is really helpful to me especially during this period of covid-19 pandemic when most universities in my country only offer online classes. Great stuff

Great Brief Explanation, thanks

So helpful to me as a student

GradCoach is a fantastic site with brilliant and modern minds behind it.. I spent weeks decoding the substantial academic Jargon and grounding my initial steps on the research process, which could be shortened to a couple of days through the Gradcoach. Thanks again!

This is an amazing talk. I paved way for myself as a researcher. Thank you GradCoach!

Well-presented overview of the literature!

This was brilliant. So clear. Thank you

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• University of Texas Libraries

Literature Reviews

• What is a literature review?
• Steps in the Literature Review Process
• Define your research question
• Determine inclusion and exclusion criteria
• Choose databases and search
• Review Results
• Synthesize Results
• Analyze Results
• Librarian Support
• Artificial Intelligence (AI) Tools

What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

Meryl Brodsky : Communication and Information Studies

Hannah Chapman Tripp : Biology, Neuroscience

Carolyn Cunningham : Human Development & Family Sciences, Psychology, Sociology

Larayne Dallas : Engineering

Janelle Hedstrom : Special Education, Curriculum & Instruction, Ed Leadership & Policy ​

Susan Macicak : Linguistics

Imelda Vetter : Dell Medical School

For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

• October 26, 2022 recording
• Last Updated: Aug 13, 2024 1:52 PM
• URL: https://guides.lib.utexas.edu/literaturereviews

Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

• Roughly how many sources should you include?
• What types of sources (books, journal articles, websites)?
• Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
• Should you evaluate your sources?
• Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

• Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
• Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
• Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

• Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
• By publication: Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
• By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
• Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
• Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of your organizational strategy. In other words, a chronological review would have subsections for each vital time period. A thematic review would have subtopics based upon factors that relate to the theme or issue.

Sometimes, though, you might need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. Put in only what is necessary. Here are a few other sections you might want to consider:

• Current Situation: Information necessary to understand the topic or focus of the literature review.
• History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

Questions for Further Research: What questions about the field has the review sparked? How will you further your research as a result of the review?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid.

Be selective

Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

Use caution when paraphrasing

When paraphrasing a source that is not your own, be sure to represent the author’s information or opinions accurately and in your own words. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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Foundational Research Writing, Background Discussion and Literature Review for CS, IS and CY

• First Online: 25 May 2023

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• Uche M. Mbanaso 4 ,
• Lucienne Abrahams 5 &
• Kennedy Chinedu Okafor 6  

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This chapter is dedicated to explaining the skills a researcher needs, the types of background information required to support the research enquiry and the literature review that enables the researcher to situate the research in the context of existing research, while addressing the gap in knowledge. It explains how the research problem statement, the heart of the research, is the basis for building the background discussion and literature review. It illustrates the annotated bibliography technique, as a key step in the process of translating reading into academic writing. It explains different forms of background discussion and different forms of literature reviews. It shows how the literature review forms the basis for the analytical framework that will be applied to data analysis and presents an example analytical framework diagram.

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Mbanaso, U.M., Abrahams, L., Okafor, K.C. (2023). Foundational Research Writing, Background Discussion and Literature Review for CS, IS and CY. In: Research Techniques for Computer Science, Information Systems and Cybersecurity. Springer, Cham. https://doi.org/10.1007/978-3-031-30031-8_5

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• UConn Library
• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
• << Previous: Getting Started
• Next: How to Pick a Topic >>
• Last Updated: Sep 21, 2022 2:16 PM
• URL: https://guides.lib.uconn.edu/literaturereview

Writing Research Background

Research background is a brief outline of the most important studies that have been conducted so far presented in a chronological order. Research background part in introduction chapter can be also headed ‘Background of the Study.” Research background should also include a brief discussion of major theories and models related to the research problem.

Specifically, when writing research background you can discuss major theories and models related to your research problem in a chronological order to outline historical developments in the research area.  When writing research background, you also need to demonstrate how your research relates to what has been done so far in the research area.

Research background is written after the literature review. Therefore, literature review has to be the first and the longest stage in the research process, even before the formulation of research aims and objectives, right after the selection of the research area. Once the research area is selected, the literature review is commenced in order to identify gaps in the research area.

Research aims and objectives need to be closely associated with the elimination of this gap in the literature. The main difference between background of the study and literature review is that the former only provides general information about what has been done so far in the research area, whereas the latter elaborates and critically reviews previous works.

John Dudovskiy

Research Methods

• Getting Started
• Literature Review Research
• Research Design
• Research Design By Discipline
• SAGE Research Methods
• Teaching with SAGE Research Methods

Literature Review

• What is a Literature Review?
• What is NOT a Literature Review?
• Purposes of a Literature Review
• Types of Literature Reviews
• Literature Reviews vs. Systematic Reviews
• Systematic vs. Meta-Analysis

Literature Review  is a comprehensive survey of the works published in a particular field of study or line of research, usually over a specific period of time, in the form of an in-depth, critical bibliographic essay or annotated list in which attention is drawn to the most significant works.

Also, we can define a literature review as the collected body of scholarly works related to a topic:

• Summarizes and analyzes previous research relevant to a topic
• Includes scholarly books and articles published in academic journals
• Can be an specific scholarly paper or a section in a research paper

The objective of a Literature Review is to find previous published scholarly works relevant to an specific topic

• Help gather ideas or information
• Keep up to date in current trends and findings
• Help develop new questions

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Helps focus your own research questions or problems
• Discovers relationships between research studies/ideas.
• Suggests unexplored ideas or populations
• Identifies major themes, concepts, and researchers on a topic.
• Tests assumptions; may help counter preconceived ideas and remove unconscious bias.
• Identifies critical gaps, points of disagreement, or potentially flawed methodology or theoretical approaches.
• Indicates potential directions for future research.

All content in this section is from Literature Review Research from Old Dominion University 

Keep in mind the following, a literature review is NOT:

Not an essay 

Not an annotated bibliography  in which you summarize each article that you have reviewed.  A literature review goes beyond basic summarizing to focus on the critical analysis of the reviewed works and their relationship to your research question.

Not a research paper   where you select resources to support one side of an issue versus another.  A lit review should explain and consider all sides of an argument in order to avoid bias, and areas of agreement and disagreement should be highlighted.

A literature review serves several purposes. For example, it

• provides thorough knowledge of previous studies; introduces seminal works.
• helps focus one’s own research topic.
• identifies a conceptual framework for one’s own research questions or problems; indicates potential directions for future research.
• suggests previously unused or underused methodologies, designs, quantitative and qualitative strategies.
• identifies gaps in previous studies; identifies flawed methodologies and/or theoretical approaches; avoids replication of mistakes.
• helps the researcher avoid repetition of earlier research.
• suggests unexplored populations.
• determines whether past studies agree or disagree; identifies controversy in the literature.
• tests assumptions; may help counter preconceived ideas and remove unconscious bias.

As Kennedy (2007) notes*, it is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally that become part of the lore of field. In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature."  Educational Researcher  36 (April 2007): 139-147.

All content in this section is from The Literature Review created by Dr. Robert Larabee USC

Robinson, P. and Lowe, J. (2015),  Literature reviews vs systematic reviews.  Australian and New Zealand Journal of Public Health, 39: 103-103. doi: 10.1111/1753-6405.12393

What's in the name? The difference between a Systematic Review and a Literature Review, and why it matters . By Lynn Kysh from University of Southern California

Systematic review or meta-analysis?

A  systematic review  answers a defined research question by collecting and summarizing all empirical evidence that fits pre-specified eligibility criteria.

A  meta-analysis  is the use of statistical methods to summarize the results of these studies.

Systematic reviews, just like other research articles, can be of varying quality. They are a significant piece of work (the Centre for Reviews and Dissemination at York estimates that a team will take 9-24 months), and to be useful to other researchers and practitioners they should have:

• clearly stated objectives with pre-defined eligibility criteria for studies
• explicit, reproducible methodology
• a systematic search that attempts to identify all studies
• assessment of the validity of the findings of the included studies (e.g. risk of bias)
• systematic presentation, and synthesis, of the characteristics and findings of the included studies

Not all systematic reviews contain meta-analysis. 

Meta-analysis is the use of statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review.  More information on meta-analyses can be found in  Cochrane Handbook, Chapter 9 .

A meta-analysis goes beyond critique and integration and conducts secondary statistical analysis on the outcomes of similar studies.  It is a systematic review that uses quantitative methods to synthesize and summarize the results.

An advantage of a meta-analysis is the ability to be completely objective in evaluating research findings.  Not all topics, however, have sufficient research evidence to allow a meta-analysis to be conducted.  In that case, an integrative review is an appropriate strategy. 

Some of the content in this section is from Systematic reviews and meta-analyses: step by step guide created by Kate McAllister.

• << Previous: Getting Started
• Next: Research Design >>
• Last Updated: Jul 15, 2024 10:34 AM
• URL: https://guides.lib.udel.edu/researchmethods

Writing the parts of scientific reports

19 Writing the literature review or background chapter

The more advanced you are in your studies, the more important it will be to make the connection between your own research and the research of others. Therefore, when you begin a project or have identified a research question, you usually go and search for relevant work done by others.

The literature review consists of two parts (Ridely, 2012): the finished product which is part of a thesis and the process which is searching and critically reading the work done by others, which is often called literature search or in this book literature – based research .  So, the purpose of what is called literature review is initially often to read around the subject, to explore the field and gain a thorough understanding of current work and perspectives. However, this reviewing of literature is an ongoing activity and lasts until the day you complete the final draft because understanding and comparing with existing literature can help you to analyse and interpret your results.

Purpose of the literature review

The purposes of a literature review can be summarized as follows:

• To provide a historical background for your research.
• To explore the current context in which your research is situated by referring to debates, issues or questions in the field, which helps to show the significance of a problem for research.
• To identify a discussion of relevant theories and concepts, which you then will probably draw on.
• To gain an overview of relevant methodology or methods used to collect and analyse data in a particular field.
• To clarify and introduce relevant terminology to be used in your research.
• To identify relevant research and to show how your work extends or challenges it.
• To establish a gap in the work in the field.
• To provide supporting evidence for a problem or claim.

When is a specific literature review chapter required?

Even though no research can be done without knowledge of and referring to relevant research of others, your (primary) purposes and whether you will write a dedicated chapter with the title Literature review depends on the kind of research project and the conventions within your discipline. There is for example a significant difference between applied and theoretical research, where more extensive and critical literature reviews are expected. There are further significant differences between research done at the beginning of your university studies or for a BA, BSc, MA, MSc or PhD thesis. For a Master or PhD thesis a high level of awareness of the research done in your field and deep and broad discussion of it is expected.

However, the insights from your literature review will strongly influence the content of other chapters, such as the Background (if you include such a section in your study) or the Methodology section . As already mentioned, you very often refer to theory (i.e. literature) when analysing and interpreting data in the Discussion section .

Overall structure

If you include a separate chapter with the title literature review, you can follow the principle below. As always organize your writing along a general-to-specific pattern:

Academic Writing in a Swiss University Context Copyright © 2018 by Irene Dietrichs. All Rights Reserved.

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Library services for undergraduate research.

• Creating an Abstract
• What is a Literature Review?
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Literature Review: A Definition

What is a literature review, then.

A literature review discusses and analyses published information in a particular subject area.   Sometimes the information covers a certain time period.

A literature review is more than a summary of the sources, it has an organizational pattern that combines both summary and synthesis. A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

While the main focus of an academic research paper is to support your own argument, the focus of a literature review is to summarize and synthesize the arguments and ideas of others. The academic research paper also covers a range of sources, but it is usually a select number of sources, because the emphasis is on the argument. Likewise, a literature review can also have an "argument," but it is not as important as covering a number of sources. In short, an academic research paper and a literature review contain some of the same elements. In fact, many academic research papers will contain a literature review section. What aspect of the study (either the argument or the sources) that is emphasized determines what type of document it is.

( "Literature Reviews" from The Writing Center, University of North Carolina at Chapel Hill )

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone.

For professionals, they are useful reports that keep them up to date with what is current in the field.

For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper's investigation.

Comprehensive knowledge of the literature of the field is essential to most research papers.

Journal Articles on Writing Literature Reviews

• Research Methods for Comprehensive Science Literature Reviews Author: Brown,Barry N. Journal: Issues in Science & Technology Librarianship Date: Spring2009 Issue: 57 Page: 1 more... less... Finding some information on most topics is easy. There are abundant sources of information readily available. However, completing a comprehensive literature review on a particular topic is often difficult, laborious, and time intensive; the project requires organization, persistence, and an understanding of the scholarly communication and publishing process. This paper briefly outlines methods of conducting a comprehensive literature review for science topics. [ABSTRACT FROM AUTHOR];
• Research: Considerations in Writing a Literature Review Authors: Black,K. Journal: The New Social Worker Date: 01/01; 2007 Volume: 14 Issue: 2 Page: 12 more... less... Literature reviews are ubiquitous in academic journals, scholarly reports, and social work education. Conducting and writing a good literature review is both personally and professionally satisfying. (Journal abstract).
• How to do (or not to do) A Critical Literature Review Authors: Jesson,Jill; Lacey,Fiona Journal: Pharmacy Education Pub Date: 2006 Volume: 6 Issue: 2 Pages:139 - 148 more... less... More and more students are required to perform a critical literature review as part of their undergraduate or postgraduate studies. Whilst most of the latest research methods textbooks advise how to do a literature search, very few cover the literature review. This paper covers two types of review: a critical literature review and a systematic review. [ABSTRACT FROM AUTHOR]
• Conducting a Literature Review Authors: Rowley,Jennifer; Slack,Frances Journal: Management Research News Pub Date: 2004 Volume: 27 Issue: 6 Pages:31-39 more... less... Abstract: This article offers support and guidance for students undertaking a literature review as part of their dissertation during an undergraduate or Masters course. A literature review is a summary of a subject field that supports the identification of specific research questions. A literature review needs to draw on and evaluate a range of different types of sources including academic and professional journal articles, books, and web-based resources. The literature search helps in the identification and location of relevant documents and other sources. Search engines can be used to search web resources and bibliographic databases. Conceptual frameworks can be a useful tool in developing an understanding of a subject area. Creating the literature review involves the stages of: scanning, making notes, structuring the literature review, writing the literature review, and building a bibliography.

Some Books from the WU Catalog

• The SAGE handbook of visual research methods [electronic resource] by Edited by Luc Pauwels and Dawn Mannay. ISBN: 9781526417015 Publication Date: SAGE Publications, Inc., 2020.

Helpful Websites

• "How to do a Literature Review" from Ferdinand D. Bluford Library
• "The Literature Review: A Few Tips on Conducting It." from the University of Toronto
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• Next: Creating a Poster >>
• Last Updated: Jul 24, 2024 3:18 PM
• URL: https://libguides.wustl.edu/our

How do I Write a Literature Review?: #5 Writing the Review

• Step #1: Choosing a Topic
• Step #2: Finding Information
• Step #3: Evaluating Content
• Step #4: Synthesizing Content
• #5 Writing the Review
• Citing Your Sources

WRITING THE REVIEW 

You've done the research and now you're ready to put your findings down on paper. When preparing to write your review, first consider how will you organize your review.

The actual review generally has 5 components:

Abstract  -  An abstract is a summary of your literature review. It is made up of the following parts:

• A contextual sentence about your motivation behind your research topic
• Your thesis statement
• A descriptive statement about the types of literature used in the review
• Summarize your findings
• Conclusion(s) based upon your findings

Introduction :   Like a typical research paper introduction, provide the reader with a quick idea of the topic of the literature review:

• Define or identify the general topic, issue, or area of concern. This provides the reader with context for reviewing the literature.
• Identify related trends in what has already been published about the topic; or conflicts in theory, methodology, evidence, and conclusions; or gaps in research and scholarship; or a single problem or new perspective of immediate interest.
• Establish your reason (point of view) for reviewing the literature; explain the criteria to be used in analyzing and comparing literature and the organization of the review (sequence); and, when necessary, state why certain literature is or is not included (scope)  - 

Body :  The body of a literature review contains your discussion of sources and can be organized in 3 ways-

• Chronological -  by publication or by trend
• Thematic -  organized around a topic or issue, rather than the progression of time
• Methodical -  the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the "methods" of the literature's researcher or writer that you are reviewing

You may also want to include a section on "questions for further research" and discuss what questions the review has sparked about the topic/field or offer suggestions for future studies/examinations that build on your current findings.

Conclusion :  In the conclusion, you should:

Conclude your paper by providing your reader with some perspective on the relationship between your literature review's specific topic and how it's related to it's parent discipline, scientific endeavor, or profession.

Bibliography :   Since a literature review is composed of pieces of research, it is very important that your correctly cite the literature you are reviewing, both in the reviews body as well as in a bibliography/works cited. To learn more about different citation styles, visit the " Citing Your Sources " tab.

• Writing a Literature Review: Wesleyan University
• Literature Review: Edith Cowan University
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• Next: Citing Your Sources >>
• Last Updated: Aug 22, 2023 1:35 PM
• URL: https://libguides.eastern.edu/literature_reviews

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• v.21(3); Fall 2022

Literature Reviews, Theoretical Frameworks, and Conceptual Frameworks: An Introduction for New Biology Education Researchers

Julie a. luft.

† Department of Mathematics, Social Studies, and Science Education, Mary Frances Early College of Education, University of Georgia, Athens, GA 30602-7124

Sophia Jeong

‡ Department of Teaching & Learning, College of Education & Human Ecology, Ohio State University, Columbus, OH 43210

Robert Idsardi

§ Department of Biology, Eastern Washington University, Cheney, WA 99004

Grant Gardner

∥ Department of Biology, Middle Tennessee State University, Murfreesboro, TN 37132

Associated Data

To frame their work, biology education researchers need to consider the role of literature reviews, theoretical frameworks, and conceptual frameworks as critical elements of the research and writing process. However, these elements can be confusing for scholars new to education research. This Research Methods article is designed to provide an overview of each of these elements and delineate the purpose of each in the educational research process. We describe what biology education researchers should consider as they conduct literature reviews, identify theoretical frameworks, and construct conceptual frameworks. Clarifying these different components of educational research studies can be helpful to new biology education researchers and the biology education research community at large in situating their work in the broader scholarly literature.

INTRODUCTION

Discipline-based education research (DBER) involves the purposeful and situated study of teaching and learning in specific disciplinary areas ( Singer et al. , 2012 ). Studies in DBER are guided by research questions that reflect disciplines’ priorities and worldviews. Researchers can use quantitative data, qualitative data, or both to answer these research questions through a variety of methodological traditions. Across all methodologies, there are different methods associated with planning and conducting educational research studies that include the use of surveys, interviews, observations, artifacts, or instruments. Ensuring the coherence of these elements to the discipline’s perspective also involves situating the work in the broader scholarly literature. The tools for doing this include literature reviews, theoretical frameworks, and conceptual frameworks. However, the purpose and function of each of these elements is often confusing to new education researchers. The goal of this article is to introduce new biology education researchers to these three important elements important in DBER scholarship and the broader educational literature.

The first element we discuss is a review of research (literature reviews), which highlights the need for a specific research question, study problem, or topic of investigation. Literature reviews situate the relevance of the study within a topic and a field. The process may seem familiar to science researchers entering DBER fields, but new researchers may still struggle in conducting the review. Booth et al. (2016b) highlight some of the challenges novice education researchers face when conducting a review of literature. They point out that novice researchers struggle in deciding how to focus the review, determining the scope of articles needed in the review, and knowing how to be critical of the articles in the review. Overcoming these challenges (and others) can help novice researchers construct a sound literature review that can inform the design of the study and help ensure the work makes a contribution to the field.

The second and third highlighted elements are theoretical and conceptual frameworks. These guide biology education research (BER) studies, and may be less familiar to science researchers. These elements are important in shaping the construction of new knowledge. Theoretical frameworks offer a way to explain and interpret the studied phenomenon, while conceptual frameworks clarify assumptions about the studied phenomenon. Despite the importance of these constructs in educational research, biology educational researchers have noted the limited use of theoretical or conceptual frameworks in published work ( DeHaan, 2011 ; Dirks, 2011 ; Lo et al. , 2019 ). In reviewing articles published in CBE—Life Sciences Education ( LSE ) between 2015 and 2019, we found that fewer than 25% of the research articles had a theoretical or conceptual framework (see the Supplemental Information), and at times there was an inconsistent use of theoretical and conceptual frameworks. Clearly, these frameworks are challenging for published biology education researchers, which suggests the importance of providing some initial guidance to new biology education researchers.

Fortunately, educational researchers have increased their explicit use of these frameworks over time, and this is influencing educational research in science, technology, engineering, and mathematics (STEM) fields. For instance, a quick search for theoretical or conceptual frameworks in the abstracts of articles in Educational Research Complete (a common database for educational research) in STEM fields demonstrates a dramatic change over the last 20 years: from only 778 articles published between 2000 and 2010 to 5703 articles published between 2010 and 2020, a more than sevenfold increase. Greater recognition of the importance of these frameworks is contributing to DBER authors being more explicit about such frameworks in their studies.

Collectively, literature reviews, theoretical frameworks, and conceptual frameworks work to guide methodological decisions and the elucidation of important findings. Each offers a different perspective on the problem of study and is an essential element in all forms of educational research. As new researchers seek to learn about these elements, they will find different resources, a variety of perspectives, and many suggestions about the construction and use of these elements. The wide range of available information can overwhelm the new researcher who just wants to learn the distinction between these elements or how to craft them adequately.

Our goal in writing this paper is not to offer specific advice about how to write these sections in scholarly work. Instead, we wanted to introduce these elements to those who are new to BER and who are interested in better distinguishing one from the other. In this paper, we share the purpose of each element in BER scholarship, along with important points on its construction. We also provide references for additional resources that may be beneficial to better understanding each element. Table 1 summarizes the key distinctions among these elements.

Comparison of literature reviews, theoretical frameworks, and conceptual reviews

This article is written for the new biology education researcher who is just learning about these different elements or for scientists looking to become more involved in BER. It is a result of our own work as science education and biology education researchers, whether as graduate students and postdoctoral scholars or newly hired and established faculty members. This is the article we wish had been available as we started to learn about these elements or discussed them with new educational researchers in biology.

LITERATURE REVIEWS

Purpose of a literature review.

A literature review is foundational to any research study in education or science. In education, a well-conceptualized and well-executed review provides a summary of the research that has already been done on a specific topic and identifies questions that remain to be answered, thus illustrating the current research project’s potential contribution to the field and the reasoning behind the methodological approach selected for the study ( Maxwell, 2012 ). BER is an evolving disciplinary area that is redefining areas of conceptual emphasis as well as orientations toward teaching and learning (e.g., Labov et al. , 2010 ; American Association for the Advancement of Science, 2011 ; Nehm, 2019 ). As a result, building comprehensive, critical, purposeful, and concise literature reviews can be a challenge for new biology education researchers.

Building Literature Reviews

There are different ways to approach and construct a literature review. Booth et al. (2016a) provide an overview that includes, for example, scoping reviews, which are focused only on notable studies and use a basic method of analysis, and integrative reviews, which are the result of exhaustive literature searches across different genres. Underlying each of these different review processes are attention to the s earch process, a ppraisa l of articles, s ynthesis of the literature, and a nalysis: SALSA ( Booth et al. , 2016a ). This useful acronym can help the researcher focus on the process while building a specific type of review.

However, new educational researchers often have questions about literature reviews that are foundational to SALSA or other approaches. Common questions concern determining which literature pertains to the topic of study or the role of the literature review in the design of the study. This section addresses such questions broadly while providing general guidance for writing a narrative literature review that evaluates the most pertinent studies.

The literature review process should begin before the research is conducted. As Boote and Beile (2005 , p. 3) suggested, researchers should be “scholars before researchers.” They point out that having a good working knowledge of the proposed topic helps illuminate avenues of study. Some subject areas have a deep body of work to read and reflect upon, providing a strong foundation for developing the research question(s). For instance, the teaching and learning of evolution is an area of long-standing interest in the BER community, generating many studies (e.g., Perry et al. , 2008 ; Barnes and Brownell, 2016 ) and reviews of research (e.g., Sickel and Friedrichsen, 2013 ; Ziadie and Andrews, 2018 ). Emerging areas of BER include the affective domain, issues of transfer, and metacognition ( Singer et al. , 2012 ). Many studies in these areas are transdisciplinary and not always specific to biology education (e.g., Rodrigo-Peiris et al. , 2018 ; Kolpikova et al. , 2019 ). These newer areas may require reading outside BER; fortunately, summaries of some of these topics can be found in the Current Insights section of the LSE website.

In focusing on a specific problem within a broader research strand, a new researcher will likely need to examine research outside BER. Depending upon the area of study, the expanded reading list might involve a mix of BER, DBER, and educational research studies. Determining the scope of the reading is not always straightforward. A simple way to focus one’s reading is to create a “summary phrase” or “research nugget,” which is a very brief descriptive statement about the study. It should focus on the essence of the study, for example, “first-year nonmajor students’ understanding of evolution,” “metacognitive prompts to enhance learning during biochemistry,” or “instructors’ inquiry-based instructional practices after professional development programming.” This type of phrase should help a new researcher identify two or more areas to review that pertain to the study. Focusing on recent research in the last 5 years is a good first step. Additional studies can be identified by reading relevant works referenced in those articles. It is also important to read seminal studies that are more than 5 years old. Reading a range of studies should give the researcher the necessary command of the subject in order to suggest a research question.

Given that the research question(s) arise from the literature review, the review should also substantiate the selected methodological approach. The review and research question(s) guide the researcher in determining how to collect and analyze data. Often the methodological approach used in a study is selected to contribute knowledge that expands upon what has been published previously about the topic (see Institute of Education Sciences and National Science Foundation, 2013 ). An emerging topic of study may need an exploratory approach that allows for a description of the phenomenon and development of a potential theory. This could, but not necessarily, require a methodological approach that uses interviews, observations, surveys, or other instruments. An extensively studied topic may call for the additional understanding of specific factors or variables; this type of study would be well suited to a verification or a causal research design. These could entail a methodological approach that uses valid and reliable instruments, observations, or interviews to determine an effect in the studied event. In either of these examples, the researcher(s) may use a qualitative, quantitative, or mixed methods methodological approach.

Even with a good research question, there is still more reading to be done. The complexity and focus of the research question dictates the depth and breadth of the literature to be examined. Questions that connect multiple topics can require broad literature reviews. For instance, a study that explores the impact of a biology faculty learning community on the inquiry instruction of faculty could have the following review areas: learning communities among biology faculty, inquiry instruction among biology faculty, and inquiry instruction among biology faculty as a result of professional learning. Biology education researchers need to consider whether their literature review requires studies from different disciplines within or outside DBER. For the example given, it would be fruitful to look at research focused on learning communities with faculty in STEM fields or in general education fields that result in instructional change. It is important not to be too narrow or too broad when reading. When the conclusions of articles start to sound similar or no new insights are gained, the researcher likely has a good foundation for a literature review. This level of reading should allow the researcher to demonstrate a mastery in understanding the researched topic, explain the suitability of the proposed research approach, and point to the need for the refined research question(s).

The literature review should include the researcher’s evaluation and critique of the selected studies. A researcher may have a large collection of studies, but not all of the studies will follow standards important in the reporting of empirical work in the social sciences. The American Educational Research Association ( Duran et al. , 2006 ), for example, offers a general discussion about standards for such work: an adequate review of research informing the study, the existence of sound and appropriate data collection and analysis methods, and appropriate conclusions that do not overstep or underexplore the analyzed data. The Institute of Education Sciences and National Science Foundation (2013) also offer Common Guidelines for Education Research and Development that can be used to evaluate collected studies.

Because not all journals adhere to such standards, it is important that a researcher review each study to determine the quality of published research, per the guidelines suggested earlier. In some instances, the research may be fatally flawed. Examples of such flaws include data that do not pertain to the question, a lack of discussion about the data collection, poorly constructed instruments, or an inadequate analysis. These types of errors result in studies that are incomplete, error-laden, or inaccurate and should be excluded from the review. Most studies have limitations, and the author(s) often make them explicit. For instance, there may be an instructor effect, recognized bias in the analysis, or issues with the sample population. Limitations are usually addressed by the research team in some way to ensure a sound and acceptable research process. Occasionally, the limitations associated with the study can be significant and not addressed adequately, which leaves a consequential decision in the hands of the researcher. Providing critiques of studies in the literature review process gives the reader confidence that the researcher has carefully examined relevant work in preparation for the study and, ultimately, the manuscript.

A solid literature review clearly anchors the proposed study in the field and connects the research question(s), the methodological approach, and the discussion. Reviewing extant research leads to research questions that will contribute to what is known in the field. By summarizing what is known, the literature review points to what needs to be known, which in turn guides decisions about methodology. Finally, notable findings of the new study are discussed in reference to those described in the literature review.

Within published BER studies, literature reviews can be placed in different locations in an article. When included in the introductory section of the study, the first few paragraphs of the manuscript set the stage, with the literature review following the opening paragraphs. Cooper et al. (2019) illustrate this approach in their study of course-based undergraduate research experiences (CUREs). An introduction discussing the potential of CURES is followed by an analysis of the existing literature relevant to the design of CUREs that allows for novel student discoveries. Within this review, the authors point out contradictory findings among research on novel student discoveries. This clarifies the need for their study, which is described and highlighted through specific research aims.

A literature reviews can also make up a separate section in a paper. For example, the introduction to Todd et al. (2019) illustrates the need for their research topic by highlighting the potential of learning progressions (LPs) and suggesting that LPs may help mitigate learning loss in genetics. At the end of the introduction, the authors state their specific research questions. The review of literature following this opening section comprises two subsections. One focuses on learning loss in general and examines a variety of studies and meta-analyses from the disciplines of medical education, mathematics, and reading. The second section focuses specifically on LPs in genetics and highlights student learning in the midst of LPs. These separate reviews provide insights into the stated research question.

Suggestions and Advice

A well-conceptualized, comprehensive, and critical literature review reveals the understanding of the topic that the researcher brings to the study. Literature reviews should not be so big that there is no clear area of focus; nor should they be so narrow that no real research question arises. The task for a researcher is to craft an efficient literature review that offers a critical analysis of published work, articulates the need for the study, guides the methodological approach to the topic of study, and provides an adequate foundation for the discussion of the findings.

In our own writing of literature reviews, there are often many drafts. An early draft may seem well suited to the study because the need for and approach to the study are well described. However, as the results of the study are analyzed and findings begin to emerge, the existing literature review may be inadequate and need revision. The need for an expanded discussion about the research area can result in the inclusion of new studies that support the explanation of a potential finding. The literature review may also prove to be too broad. Refocusing on a specific area allows for more contemplation of a finding.

It should be noted that there are different types of literature reviews, and many books and articles have been written about the different ways to embark on these types of reviews. Among these different resources, the following may be helpful in considering how to refine the review process for scholarly journals:

• Booth, A., Sutton, A., & Papaioannou, D. (2016a). Systemic approaches to a successful literature review (2nd ed.). Los Angeles, CA: Sage. This book addresses different types of literature reviews and offers important suggestions pertaining to defining the scope of the literature review and assessing extant studies.
• Booth, W. C., Colomb, G. G., Williams, J. M., Bizup, J., & Fitzgerald, W. T. (2016b). The craft of research (4th ed.). Chicago: University of Chicago Press. This book can help the novice consider how to make the case for an area of study. While this book is not specifically about literature reviews, it offers suggestions about making the case for your study.
• Galvan, J. L., & Galvan, M. C. (2017). Writing literature reviews: A guide for students of the social and behavioral sciences (7th ed.). Routledge. This book offers guidance on writing different types of literature reviews. For the novice researcher, there are useful suggestions for creating coherent literature reviews.

THEORETICAL FRAMEWORKS

Purpose of theoretical frameworks.

As new education researchers may be less familiar with theoretical frameworks than with literature reviews, this discussion begins with an analogy. Envision a biologist, chemist, and physicist examining together the dramatic effect of a fog tsunami over the ocean. A biologist gazing at this phenomenon may be concerned with the effect of fog on various species. A chemist may be interested in the chemical composition of the fog as water vapor condenses around bits of salt. A physicist may be focused on the refraction of light to make fog appear to be “sitting” above the ocean. While observing the same “objective event,” the scientists are operating under different theoretical frameworks that provide a particular perspective or “lens” for the interpretation of the phenomenon. Each of these scientists brings specialized knowledge, experiences, and values to this phenomenon, and these influence the interpretation of the phenomenon. The scientists’ theoretical frameworks influence how they design and carry out their studies and interpret their data.

Within an educational study, a theoretical framework helps to explain a phenomenon through a particular lens and challenges and extends existing knowledge within the limitations of that lens. Theoretical frameworks are explicitly stated by an educational researcher in the paper’s framework, theory, or relevant literature section. The framework shapes the types of questions asked, guides the method by which data are collected and analyzed, and informs the discussion of the results of the study. It also reveals the researcher’s subjectivities, for example, values, social experience, and viewpoint ( Allen, 2017 ). It is essential that a novice researcher learn to explicitly state a theoretical framework, because all research questions are being asked from the researcher’s implicit or explicit assumptions of a phenomenon of interest ( Schwandt, 2000 ).

Selecting Theoretical Frameworks

Theoretical frameworks are one of the most contemplated elements in our work in educational research. In this section, we share three important considerations for new scholars selecting a theoretical framework.

The first step in identifying a theoretical framework involves reflecting on the phenomenon within the study and the assumptions aligned with the phenomenon. The phenomenon involves the studied event. There are many possibilities, for example, student learning, instructional approach, or group organization. A researcher holds assumptions about how the phenomenon will be effected, influenced, changed, or portrayed. It is ultimately the researcher’s assumption(s) about the phenomenon that aligns with a theoretical framework. An example can help illustrate how a researcher’s reflection on the phenomenon and acknowledgment of assumptions can result in the identification of a theoretical framework.

In our example, a biology education researcher may be interested in exploring how students’ learning of difficult biological concepts can be supported by the interactions of group members. The phenomenon of interest is the interactions among the peers, and the researcher assumes that more knowledgeable students are important in supporting the learning of the group. As a result, the researcher may draw on Vygotsky’s (1978) sociocultural theory of learning and development that is focused on the phenomenon of student learning in a social setting. This theory posits the critical nature of interactions among students and between students and teachers in the process of building knowledge. A researcher drawing upon this framework holds the assumption that learning is a dynamic social process involving questions and explanations among students in the classroom and that more knowledgeable peers play an important part in the process of building conceptual knowledge.

It is important to state at this point that there are many different theoretical frameworks. Some frameworks focus on learning and knowing, while other theoretical frameworks focus on equity, empowerment, or discourse. Some frameworks are well articulated, and others are still being refined. For a new researcher, it can be challenging to find a theoretical framework. Two of the best ways to look for theoretical frameworks is through published works that highlight different frameworks.

When a theoretical framework is selected, it should clearly connect to all parts of the study. The framework should augment the study by adding a perspective that provides greater insights into the phenomenon. It should clearly align with the studies described in the literature review. For instance, a framework focused on learning would correspond to research that reported different learning outcomes for similar studies. The methods for data collection and analysis should also correspond to the framework. For instance, a study about instructional interventions could use a theoretical framework concerned with learning and could collect data about the effect of the intervention on what is learned. When the data are analyzed, the theoretical framework should provide added meaning to the findings, and the findings should align with the theoretical framework.

A study by Jensen and Lawson (2011) provides an example of how a theoretical framework connects different parts of the study. They compared undergraduate biology students in heterogeneous and homogeneous groups over the course of a semester. Jensen and Lawson (2011) assumed that learning involved collaboration and more knowledgeable peers, which made Vygotsky’s (1978) theory a good fit for their study. They predicted that students in heterogeneous groups would experience greater improvement in their reasoning abilities and science achievements with much of the learning guided by the more knowledgeable peers.

In the enactment of the study, they collected data about the instruction in traditional and inquiry-oriented classes, while the students worked in homogeneous or heterogeneous groups. To determine the effect of working in groups, the authors also measured students’ reasoning abilities and achievement. Each data-collection and analysis decision connected to understanding the influence of collaborative work.

Their findings highlighted aspects of Vygotsky’s (1978) theory of learning. One finding, for instance, posited that inquiry instruction, as a whole, resulted in reasoning and achievement gains. This links to Vygotsky (1978) , because inquiry instruction involves interactions among group members. A more nuanced finding was that group composition had a conditional effect. Heterogeneous groups performed better with more traditional and didactic instruction, regardless of the reasoning ability of the group members. Homogeneous groups worked better during interaction-rich activities for students with low reasoning ability. The authors attributed the variation to the different types of helping behaviors of students. High-performing students provided the answers, while students with low reasoning ability had to work collectively through the material. In terms of Vygotsky (1978) , this finding provided new insights into the learning context in which productive interactions can occur for students.

Another consideration in the selection and use of a theoretical framework pertains to its orientation to the study. This can result in the theoretical framework prioritizing individuals, institutions, and/or policies ( Anfara and Mertz, 2014 ). Frameworks that connect to individuals, for instance, could contribute to understanding their actions, learning, or knowledge. Institutional frameworks, on the other hand, offer insights into how institutions, organizations, or groups can influence individuals or materials. Policy theories provide ways to understand how national or local policies can dictate an emphasis on outcomes or instructional design. These different types of frameworks highlight different aspects in an educational setting, which influences the design of the study and the collection of data. In addition, these different frameworks offer a way to make sense of the data. Aligning the data collection and analysis with the framework ensures that a study is coherent and can contribute to the field.

New understandings emerge when different theoretical frameworks are used. For instance, Ebert-May et al. (2015) prioritized the individual level within conceptual change theory (see Posner et al. , 1982 ). In this theory, an individual’s knowledge changes when it no longer fits the phenomenon. Ebert-May et al. (2015) designed a professional development program challenging biology postdoctoral scholars’ existing conceptions of teaching. The authors reported that the biology postdoctoral scholars’ teaching practices became more student-centered as they were challenged to explain their instructional decision making. According to the theory, the biology postdoctoral scholars’ dissatisfaction in their descriptions of teaching and learning initiated change in their knowledge and instruction. These results reveal how conceptual change theory can explain the learning of participants and guide the design of professional development programming.

The communities of practice (CoP) theoretical framework ( Lave, 1988 ; Wenger, 1998 ) prioritizes the institutional level , suggesting that learning occurs when individuals learn from and contribute to the communities in which they reside. Grounded in the assumption of community learning, the literature on CoP suggests that, as individuals interact regularly with the other members of their group, they learn about the rules, roles, and goals of the community ( Allee, 2000 ). A study conducted by Gehrke and Kezar (2017) used the CoP framework to understand organizational change by examining the involvement of individual faculty engaged in a cross-institutional CoP focused on changing the instructional practice of faculty at each institution. In the CoP, faculty members were involved in enhancing instructional materials within their department, which aligned with an overarching goal of instituting instruction that embraced active learning. Not surprisingly, Gehrke and Kezar (2017) revealed that faculty who perceived the community culture as important in their work cultivated institutional change. Furthermore, they found that institutional change was sustained when key leaders served as mentors and provided support for faculty, and as faculty themselves developed into leaders. This study reveals the complexity of individual roles in a COP in order to support institutional instructional change.

It is important to explicitly state the theoretical framework used in a study, but elucidating a theoretical framework can be challenging for a new educational researcher. The literature review can help to identify an applicable theoretical framework. Focal areas of the review or central terms often connect to assumptions and assertions associated with the framework that pertain to the phenomenon of interest. Another way to identify a theoretical framework is self-reflection by the researcher on personal beliefs and understandings about the nature of knowledge the researcher brings to the study ( Lysaght, 2011 ). In stating one’s beliefs and understandings related to the study (e.g., students construct their knowledge, instructional materials support learning), an orientation becomes evident that will suggest a particular theoretical framework. Theoretical frameworks are not arbitrary , but purposefully selected.

With experience, a researcher may find expanded roles for theoretical frameworks. Researchers may revise an existing framework that has limited explanatory power, or they may decide there is a need to develop a new theoretical framework. These frameworks can emerge from a current study or the need to explain a phenomenon in a new way. Researchers may also find that multiple theoretical frameworks are necessary to frame and explore a problem, as different frameworks can provide different insights into a problem.

Finally, it is important to recognize that choosing “x” theoretical framework does not necessarily mean a researcher chooses “y” methodology and so on, nor is there a clear-cut, linear process in selecting a theoretical framework for one’s study. In part, the nonlinear process of identifying a theoretical framework is what makes understanding and using theoretical frameworks challenging. For the novice scholar, contemplating and understanding theoretical frameworks is essential. Fortunately, there are articles and books that can help:

• Creswell, J. W. (2018). Research design: Qualitative, quantitative, and mixed methods approaches (5th ed.). Los Angeles, CA: Sage. This book provides an overview of theoretical frameworks in general educational research.
• Ding, L. (2019). Theoretical perspectives of quantitative physics education research. Physical Review Physics Education Research , 15 (2), 020101-1–020101-13. This paper illustrates how a DBER field can use theoretical frameworks.
• Nehm, R. (2019). Biology education research: Building integrative frameworks for teaching and learning about living systems. Disciplinary and Interdisciplinary Science Education Research , 1 , ar15. https://doi.org/10.1186/s43031-019-0017-6 . This paper articulates the need for studies in BER to explicitly state theoretical frameworks and provides examples of potential studies.
• Patton, M. Q. (2015). Qualitative research & evaluation methods: Integrating theory and practice . Sage. This book also provides an overview of theoretical frameworks, but for both research and evaluation.

CONCEPTUAL FRAMEWORKS

Purpose of a conceptual framework.

A conceptual framework is a description of the way a researcher understands the factors and/or variables that are involved in the study and their relationships to one another. The purpose of a conceptual framework is to articulate the concepts under study using relevant literature ( Rocco and Plakhotnik, 2009 ) and to clarify the presumed relationships among those concepts ( Rocco and Plakhotnik, 2009 ; Anfara and Mertz, 2014 ). Conceptual frameworks are different from theoretical frameworks in both their breadth and grounding in established findings. Whereas a theoretical framework articulates the lens through which a researcher views the work, the conceptual framework is often more mechanistic and malleable.

Conceptual frameworks are broader, encompassing both established theories (i.e., theoretical frameworks) and the researchers’ own emergent ideas. Emergent ideas, for example, may be rooted in informal and/or unpublished observations from experience. These emergent ideas would not be considered a “theory” if they are not yet tested, supported by systematically collected evidence, and peer reviewed. However, they do still play an important role in the way researchers approach their studies. The conceptual framework allows authors to clearly describe their emergent ideas so that connections among ideas in the study and the significance of the study are apparent to readers.

Constructing Conceptual Frameworks

Including a conceptual framework in a research study is important, but researchers often opt to include either a conceptual or a theoretical framework. Either may be adequate, but both provide greater insight into the research approach. For instance, a research team plans to test a novel component of an existing theory. In their study, they describe the existing theoretical framework that informs their work and then present their own conceptual framework. Within this conceptual framework, specific topics portray emergent ideas that are related to the theory. Describing both frameworks allows readers to better understand the researchers’ assumptions, orientations, and understanding of concepts being investigated. For example, Connolly et al. (2018) included a conceptual framework that described how they applied a theoretical framework of social cognitive career theory (SCCT) to their study on teaching programs for doctoral students. In their conceptual framework, the authors described SCCT, explained how it applied to the investigation, and drew upon results from previous studies to justify the proposed connections between the theory and their emergent ideas.

In some cases, authors may be able to sufficiently describe their conceptualization of the phenomenon under study in an introduction alone, without a separate conceptual framework section. However, incomplete descriptions of how the researchers conceptualize the components of the study may limit the significance of the study by making the research less intelligible to readers. This is especially problematic when studying topics in which researchers use the same terms for different constructs or different terms for similar and overlapping constructs (e.g., inquiry, teacher beliefs, pedagogical content knowledge, or active learning). Authors must describe their conceptualization of a construct if the research is to be understandable and useful.

There are some key areas to consider regarding the inclusion of a conceptual framework in a study. To begin with, it is important to recognize that conceptual frameworks are constructed by the researchers conducting the study ( Rocco and Plakhotnik, 2009 ; Maxwell, 2012 ). This is different from theoretical frameworks that are often taken from established literature. Researchers should bring together ideas from the literature, but they may be influenced by their own experiences as a student and/or instructor, the shared experiences of others, or thought experiments as they construct a description, model, or representation of their understanding of the phenomenon under study. This is an exercise in intellectual organization and clarity that often considers what is learned, known, and experienced. The conceptual framework makes these constructs explicitly visible to readers, who may have different understandings of the phenomenon based on their prior knowledge and experience. There is no single method to go about this intellectual work.

Reeves et al. (2016) is an example of an article that proposed a conceptual framework about graduate teaching assistant professional development evaluation and research. The authors used existing literature to create a novel framework that filled a gap in current research and practice related to the training of graduate teaching assistants. This conceptual framework can guide the systematic collection of data by other researchers because the framework describes the relationships among various factors that influence teaching and learning. The Reeves et al. (2016) conceptual framework may be modified as additional data are collected and analyzed by other researchers. This is not uncommon, as conceptual frameworks can serve as catalysts for concerted research efforts that systematically explore a phenomenon (e.g., Reynolds et al. , 2012 ; Brownell and Kloser, 2015 ).

Sabel et al. (2017) used a conceptual framework in their exploration of how scaffolds, an external factor, interact with internal factors to support student learning. Their conceptual framework integrated principles from two theoretical frameworks, self-regulated learning and metacognition, to illustrate how the research team conceptualized students’ use of scaffolds in their learning ( Figure 1 ). Sabel et al. (2017) created this model using their interpretations of these two frameworks in the context of their teaching.

Conceptual framework from Sabel et al. (2017) .

A conceptual framework should describe the relationship among components of the investigation ( Anfara and Mertz, 2014 ). These relationships should guide the researcher’s methods of approaching the study ( Miles et al. , 2014 ) and inform both the data to be collected and how those data should be analyzed. Explicitly describing the connections among the ideas allows the researcher to justify the importance of the study and the rigor of the research design. Just as importantly, these frameworks help readers understand why certain components of a system were not explored in the study. This is a challenge in education research, which is rooted in complex environments with many variables that are difficult to control.

For example, Sabel et al. (2017) stated: “Scaffolds, such as enhanced answer keys and reflection questions, can help students and instructors bridge the external and internal factors and support learning” (p. 3). They connected the scaffolds in the study to the three dimensions of metacognition and the eventual transformation of existing ideas into new or revised ideas. Their framework provides a rationale for focusing on how students use two different scaffolds, and not on other factors that may influence a student’s success (self-efficacy, use of active learning, exam format, etc.).

In constructing conceptual frameworks, researchers should address needed areas of study and/or contradictions discovered in literature reviews. By attending to these areas, researchers can strengthen their arguments for the importance of a study. For instance, conceptual frameworks can address how the current study will fill gaps in the research, resolve contradictions in existing literature, or suggest a new area of study. While a literature review describes what is known and not known about the phenomenon, the conceptual framework leverages these gaps in describing the current study ( Maxwell, 2012 ). In the example of Sabel et al. (2017) , the authors indicated there was a gap in the literature regarding how scaffolds engage students in metacognition to promote learning in large classes. Their study helps fill that gap by describing how scaffolds can support students in the three dimensions of metacognition: intelligibility, plausibility, and wide applicability. In another example, Lane (2016) integrated research from science identity, the ethic of care, the sense of belonging, and an expertise model of student success to form a conceptual framework that addressed the critiques of other frameworks. In a more recent example, Sbeglia et al. (2021) illustrated how a conceptual framework influences the methodological choices and inferences in studies by educational researchers.

Sometimes researchers draw upon the conceptual frameworks of other researchers. When a researcher’s conceptual framework closely aligns with an existing framework, the discussion may be brief. For example, Ghee et al. (2016) referred to portions of SCCT as their conceptual framework to explain the significance of their work on students’ self-efficacy and career interests. Because the authors’ conceptualization of this phenomenon aligned with a previously described framework, they briefly mentioned the conceptual framework and provided additional citations that provided more detail for the readers.

Within both the BER and the broader DBER communities, conceptual frameworks have been used to describe different constructs. For example, some researchers have used the term “conceptual framework” to describe students’ conceptual understandings of a biological phenomenon. This is distinct from a researcher’s conceptual framework of the educational phenomenon under investigation, which may also need to be explicitly described in the article. Other studies have presented a research logic model or flowchart of the research design as a conceptual framework. These constructions can be quite valuable in helping readers understand the data-collection and analysis process. However, a model depicting the study design does not serve the same role as a conceptual framework. Researchers need to avoid conflating these constructs by differentiating the researchers’ conceptual framework that guides the study from the research design, when applicable.

Explicitly describing conceptual frameworks is essential in depicting the focus of the study. We have found that being explicit in a conceptual framework means using accepted terminology, referencing prior work, and clearly noting connections between terms. This description can also highlight gaps in the literature or suggest potential contributions to the field of study. A well-elucidated conceptual framework can suggest additional studies that may be warranted. This can also spur other researchers to consider how they would approach the examination of a phenomenon and could result in a revised conceptual framework.

It can be challenging to create conceptual frameworks, but they are important. Below are two resources that could be helpful in constructing and presenting conceptual frameworks in educational research:

• Maxwell, J. A. (2012). Qualitative research design: An interactive approach (3rd ed.). Los Angeles, CA: Sage. Chapter 3 in this book describes how to construct conceptual frameworks.
• Ravitch, S. M., & Riggan, M. (2016). Reason & rigor: How conceptual frameworks guide research . Los Angeles, CA: Sage. This book explains how conceptual frameworks guide the research questions, data collection, data analyses, and interpretation of results.

CONCLUDING THOUGHTS

Literature reviews, theoretical frameworks, and conceptual frameworks are all important in DBER and BER. Robust literature reviews reinforce the importance of a study. Theoretical frameworks connect the study to the base of knowledge in educational theory and specify the researcher’s assumptions. Conceptual frameworks allow researchers to explicitly describe their conceptualization of the relationships among the components of the phenomenon under study. Table 1 provides a general overview of these components in order to assist biology education researchers in thinking about these elements.

It is important to emphasize that these different elements are intertwined. When these elements are aligned and complement one another, the study is coherent, and the study findings contribute to knowledge in the field. When literature reviews, theoretical frameworks, and conceptual frameworks are disconnected from one another, the study suffers. The point of the study is lost, suggested findings are unsupported, or important conclusions are invisible to the researcher. In addition, this misalignment may be costly in terms of time and money.

Conducting a literature review, selecting a theoretical framework, and building a conceptual framework are some of the most difficult elements of a research study. It takes time to understand the relevant research, identify a theoretical framework that provides important insights into the study, and formulate a conceptual framework that organizes the finding. In the research process, there is often a constant back and forth among these elements as the study evolves. With an ongoing refinement of the review of literature, clarification of the theoretical framework, and articulation of a conceptual framework, a sound study can emerge that makes a contribution to the field. This is the goal of BER and education research.

Supplementary Material

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Frequently asked questions

What is the difference between a literature review and a theoretical framework.

A literature review and a theoretical framework are not the same thing and cannot be used interchangeably. While a theoretical framework describes the theoretical underpinnings of your work, a literature review critically evaluates existing research relating to your topic. You’ll likely need both in your dissertation .

Frequently asked questions: Dissertation

Dissertation word counts vary widely across different fields, institutions, and levels of education:

• An undergraduate dissertation is typically 8,000–15,000 words
• A master’s dissertation is typically 12,000–50,000 words
• A PhD thesis is typically book-length: 70,000–100,000 words

However, none of these are strict guidelines – your word count may be lower or higher than the numbers stated here. Always check the guidelines provided by your university to determine how long your own dissertation should be.

A dissertation prospectus or proposal describes what or who you plan to research for your dissertation. It delves into why, when, where, and how you will do your research, as well as helps you choose a type of research to pursue. You should also determine whether you plan to pursue qualitative or quantitative methods and what your research design will look like.

It should outline all of the decisions you have taken about your project, from your dissertation topic to your hypotheses and research objectives , ready to be approved by your supervisor or committee.

Note that some departments require a defense component, where you present your prospectus to your committee orally.

A thesis is typically written by students finishing up a bachelor’s or Master’s degree. Some educational institutions, particularly in the liberal arts, have mandatory theses, but they are often not mandatory to graduate from bachelor’s degrees. It is more common for a thesis to be a graduation requirement from a Master’s degree.

Even if not mandatory, you may want to consider writing a thesis if you:

• Plan to attend graduate school soon
• Have a particular topic you’d like to study more in-depth
• Are considering a career in research
• Would like a capstone experience to tie up your academic experience

The conclusion of your thesis or dissertation should include the following:

• A restatement of your research question
• A summary of your key arguments and/or results
• A short discussion of the implications of your research

The conclusion of your thesis or dissertation shouldn’t take up more than 5–7% of your overall word count.

For a stronger dissertation conclusion , avoid including:

• Important evidence or analysis that wasn’t mentioned in the discussion section and results section
• Generic concluding phrases (e.g. “In conclusion …”)
• Weak statements that undermine your argument (e.g., “There are good points on both sides of this issue.”)

Your conclusion should leave the reader with a strong, decisive impression of your work.

While it may be tempting to present new arguments or evidence in your thesis or disseration conclusion , especially if you have a particularly striking argument you’d like to finish your analysis with, you shouldn’t. Theses and dissertations follow a more formal structure than this.

All your findings and arguments should be presented in the body of the text (more specifically in the discussion section and results section .) The conclusion is meant to summarize and reflect on the evidence and arguments you have already presented, not introduce new ones.

A theoretical framework can sometimes be integrated into a  literature review chapter , but it can also be included as its own chapter or section in your dissertation . As a rule of thumb, if your research involves dealing with a lot of complex theories, it’s a good idea to include a separate theoretical framework chapter.

While a theoretical framework describes the theoretical underpinnings of your work based on existing research, a conceptual framework allows you to draw your own conclusions, mapping out the variables you may use in your study and the interplay between them.

A thesis or dissertation outline is one of the most critical first steps in your writing process. It helps you to lay out and organize your ideas and can provide you with a roadmap for deciding what kind of research you’d like to undertake.

Generally, an outline contains information on the different sections included in your thesis or dissertation , such as:

• Your anticipated title
• Your abstract
• Your chapters (sometimes subdivided into further topics like literature review , research methods , avenues for future research, etc.)

When you mention different chapters within your text, it’s considered best to use Roman numerals for most citation styles. However, the most important thing here is to remain consistent whenever using numbers in your dissertation .

In most styles, the title page is used purely to provide information and doesn’t include any images. Ask your supervisor if you are allowed to include an image on the title page before doing so. If you do decide to include one, make sure to check whether you need permission from the creator of the image.

Include a note directly beneath the image acknowledging where it comes from, beginning with the word “ Note .” (italicized and followed by a period). Include a citation and copyright attribution . Don’t title, number, or label the image as a figure , since it doesn’t appear in your main text.

Definitional terms often fall into the category of common knowledge , meaning that they don’t necessarily have to be cited. This guidance can apply to your thesis or dissertation glossary as well.

However, if you’d prefer to cite your sources , you can follow guidance for citing dictionary entries in MLA or APA style for your glossary.

A glossary is a collection of words pertaining to a specific topic. In your thesis or dissertation, it’s a list of all terms you used that may not immediately be obvious to your reader. In contrast, an index is a list of the contents of your work organized by page number.

The title page of your thesis or dissertation goes first, before all other content or lists that you may choose to include.

The title page of your thesis or dissertation should include your name, department, institution, degree program, and submission date.

Glossaries are not mandatory, but if you use a lot of technical or field-specific terms, it may improve readability to add one to your thesis or dissertation. Your educational institution may also require them, so be sure to check their specific guidelines.

A glossary or “glossary of terms” is a collection of words pertaining to a specific topic. In your thesis or dissertation, it’s a list of all terms you used that may not immediately be obvious to your reader. Your glossary only needs to include terms that your reader may not be familiar with, and is intended to enhance their understanding of your work.

A glossary is a collection of words pertaining to a specific topic. In your thesis or dissertation, it’s a list of all terms you used that may not immediately be obvious to your reader. In contrast, dictionaries are more general collections of words.

An abbreviation is a shortened version of an existing word, such as Dr. for Doctor. In contrast, an acronym uses the first letter of each word to create a wholly new word, such as UNESCO (an acronym for the United Nations Educational, Scientific and Cultural Organization).

As a rule of thumb, write the explanation in full the first time you use an acronym or abbreviation. You can then proceed with the shortened version. However, if the abbreviation is very common (like PC, USA, or DNA), then you can use the abbreviated version from the get-go.

Be sure to add each abbreviation in your list of abbreviations !

If you only used a few abbreviations in your thesis or dissertation , you don’t necessarily need to include a list of abbreviations .

If your abbreviations are numerous, or if you think they won’t be known to your audience, it’s never a bad idea to add one. They can also improve readability, minimizing confusion about abbreviations unfamiliar to your reader.

A list of abbreviations is a list of all the abbreviations that you used in your thesis or dissertation. It should appear at the beginning of your document, with items in alphabetical order, just after your table of contents .

Your list of tables and figures should go directly after your table of contents in your thesis or dissertation.

Lists of figures and tables are often not required, and aren’t particularly common. They specifically aren’t required for APA-Style, though you should be careful to follow their other guidelines for figures and tables .

If you have many figures and tables in your thesis or dissertation, include one may help you stay organized. Your educational institution may require them, so be sure to check their guidelines.

A list of figures and tables compiles all of the figures and tables that you used in your thesis or dissertation and displays them with the page number where they can be found.

The table of contents in a thesis or dissertation always goes between your abstract and your introduction .

You may acknowledge God in your dissertation acknowledgements , but be sure to follow academic convention by also thanking the members of academia, as well as family, colleagues, and friends who helped you.

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

In a thesis or dissertation, the discussion is an in-depth exploration of the results, going into detail about the meaning of your findings and citing relevant sources to put them in context.

The conclusion is more shorter and more general: it concisely answers your main research question and makes recommendations based on your overall findings.

In the discussion , you explore the meaning and relevance of your research results , explaining how they fit with existing research and theory. Discuss:

• Your  interpretations : what do the results tell us?
• The  implications : why do the results matter?
• The  limitation s : what can’t the results tell us?

The results chapter or section simply and objectively reports what you found, without speculating on why you found these results. The discussion interprets the meaning of the results, puts them in context, and explains why they matter.

In qualitative research , results and discussion are sometimes combined. But in quantitative research , it’s considered important to separate the objective results from your interpretation of them.

Results are usually written in the past tense , because they are describing the outcome of completed actions.

The results chapter of a thesis or dissertation presents your research results concisely and objectively.

In quantitative research , for each question or hypothesis , state:

• The type of analysis used
• Relevant results in the form of descriptive and inferential statistics
• Whether or not the alternative hypothesis was supported

In qualitative research , for each question or theme, describe:

• Recurring patterns
• Significant or representative individual responses
• Relevant quotations from the data

Don’t interpret or speculate in the results chapter.

To automatically insert a table of contents in Microsoft Word, follow these steps:

• Apply heading styles throughout the document.
• In the references section in the ribbon, locate the Table of Contents group.
• Click the arrow next to the Table of Contents icon and select Custom Table of Contents.
• Select which levels of headings you would like to include in the table of contents.

Make sure to update your table of contents if you move text or change headings. To update, simply right click and select Update Field.

All level 1 and 2 headings should be included in your table of contents . That means the titles of your chapters and the main sections within them.

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What is the key difference between literature review and related work?

I really can not find a justifiable answer to this question. Are they used interchangeably? One answer that's i found to be true is that we use the term literature review in writing thesis and related work in the writing research paper. but i am not sure if it is correct or not?

• research-process
• literature-review

• 2 Can you perhaps provide an example of somewhere that you've seen "Related work" used in a relevant context? And perhaps the field that you're working in? With the information available from your question, it's not clear to me exactly what you're asking. For the most part, I'd imagine they're the same but you may have a very specific context in mind where some difference is intended. –  Ian_Fin Commented Oct 20, 2016 at 8:09
• 1 A literature review is a chapter in a monograph/thesis, and a related work is a section in a article/paper. –  Frames Catherine White Commented Jul 4, 2017 at 10:43

2 Answers 2

I've been looking last week for the difference between the literature review and the background. And I found this which may help you, a good definition of what the literature supposed to be (in my opinion): https://academia.stackexchange.com/a/49629/57676

I'm not sure, but I think the literature review can be regarded as related work in more storytelling style. And yes, related work is more frequent in research papers because you don't have enough space to "build a conceptual structure that ties together all the key ideas". Therefore, you just describe briefly what has been done and maybe try to compare it theoretically against what you're proposing, I think.

I have also faced this problem of defining the difference between these two terms. I got to write a paper to a conference and since it's my very first paper I was searching for some tutorials on youtube for 'writing a related work section in the paper'. What I found was mainly related to Literature Review. So I guess these two things are almost the same. Also, as it was said previously Literature Review is more frequent in thesises.

Maybe you may find this article useful https://guidetogradschoolsurvival.wordpress.com/2011/04/08/how-to-write-related-work/

at least for me, it was. Good luck!

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SYSTEMATIC REVIEW article

The relationship between hippocampal changes in healthy aging and alzheimer’s disease: a systematic literature review.

• 1 Austin Health, University of Melbourne, Heidelberg, VIC, Australia
• 2 Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, IL, United States
• 3 Evelyn F. McKnight Brain Institute, Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, United States
• 4 Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, TX, United States
• 5 Danone Specialised Nutrition, Hoofddorp, Netherlands

Introduction: Neurobiological changes in the hippocampus are a common consequence of aging. However, there are differences in the rate of decline and overall volume loss in people with no cognitive impairment compared to those with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). This systematic literature review was conducted to determine the relationship between hippocampal atrophy and changes in hippocampal volume in the non-cognitively impaired brain and those with MCI or AD.

Methods: This systematic review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. The PubMed database was searched up to September 15, 2022, for longitudinal magnetic resonance imaging studies reporting hippocampal atrophy or volume change in cognitively normal aging individuals and patients with MCI and/or AD. Study selection was divided into two steps: (1) identification and retrieval of relevant studies; (2) screening the studies by (a) title/abstract and (b) full text. Two teams, each consisting of two independent reviewers, determined whether the publications met the inclusion criteria for the systematic review. An evidence table was populated with data extracted from eligible publications and inclusion in the final systematic review was confirmed.

Results: The systematic search identified 357 publications that were initially screened by title/abstract, of which, 115 publications were retrieved and reviewed by full text for eligibility. Seventeen publications met the eligibility criteria; however, during data extraction, two studies were determined to not meet the inclusion criteria and were excluded. The remaining 15 studies were included in the systematic review. Overall, the results of these studies demonstrated that the hippocampus and hippocampal subfields change over time, with both decreased hippocampal volume and increased rate of hippocampal atrophy observed. Hippocampal changes in AD were observed to be greater than hippocampal changes in MCI, and changes in MCI were observed to be greater than those in normal aging populations.

Conclusion: Published literature suggests that the rate of hippocampal decline and extent of loss is on a continuum that begins in people without cognitive impairment and continues to MCI and AD, and that differences between no cognitive impairment, MCI, and AD are quantitative rather than qualitative.

Introduction

Progression of the “Alzheimer’s disease (AD) continuum” is not fully understood, with many individuals transitioning from age-related memory decline to increasingly severe cognitive impairment over a period of several years. One study estimated that by 65 years of age, the annual probabilities of transitioning to a state of more severe cognitive impairment were 8% for individuals with normal cognition, 22% for people with mild cognitive impairment (MCI) due to AD, 25% for patients with mild AD, 36% for patients with moderate AD, and 16% for patients with severe AD; with the likelihood of progression increasing with age for each cognitive state ( Davis et al., 2018 ).

It is generally accepted that brain changes begin many years prior to the clinical manifestations of AD and that the spectrum of AD can span from clinically asymptomatic to severely impaired ( Aisen et al., 2017 ). For example, a recent cohort study found that at any age, biologically-defined AD (i.e., using biofluid biomarkers: A+, T+) is more common than clinically-diagnosed probable AD (i.e., using conventional definitions based on clinical symptoms) due to many asymptomatic individuals with biological AD ( Schneider et al., 2009 ; Jack et al., 2019 ). In addition, data suggest that among individuals without cognitive impairment, a smaller hippocampal volume is associated with cognitive decline ( Fleischman et al., 2013 ).

It is well established that hippocampal volume decreases and hippocampal atrophy increases prior to the development of cognitive impairment (e.g., Fjell and Walhovd, 2010 ; Fraser et al., 2015 ; Nobis et al., 2019 ) and clinical dementia (e.g., Barnes et al., 2009 ; Peng et al., 2015 ). Research demonstrates that hippocampal volume begins to decline in midlife ( Vinke et al., 2018 ; Chauveau et al., 2021 ), with an annual loss of approximately 1.18% in individuals over the age of 50 ( Raz et al., 2004 ). Likewise, the rate of hippocampal atrophy also accelerates with increasing age ( Vinke et al., 2018 ).

While it is understood that neurobiological changes in the hippocampus are a common consequence of aging, there is evidence that the rate of decline and overall volume loss is on a continuum from no cognitive impairment to MCI to AD and that differences are quantitative rather than qualitative (e.g., Jack et al., 2000 ; Fjell et al., 2013 ; Bangen et al., 2018 ).

The objective of this systematic review is to summarize the published literature relating to hippocampal volume and hippocampal atrophy in people without cognitive impairment, with MCI, and with AD. Specifically, this systematic review asked the question: Are the hippocampal changes observed prior to the onset of cognitive impairment parallel to those found in MCI and AD?

This systematic review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology ( Page et al., 2021 ). Although the protocol was not prospectively registered, the literature search was conducted based on predetermined search terms and inclusion and exclusion criteria.

Search strategy and data source

Literature searches were run in PubMed® up to September 15, 2022. The search terms used were: “atrophy” AND “hippocamp*” AND “Alzheimer’s disease” AND “Aging” AND “Magnetic Resonance Imaging” and prefiltered for human studies only. The asterisk was used as a wildcard symbol that broadened the search by identifying all words that start with “hippocamp” (e.g., hippocampus, hippocampal, hippocampi).

The titles of all returned publications were initially screened for non-English language and duplicate records. Next, two independent reviewers screened the titles and abstracts to identify studies for full text review. The full text and Supplementary materials of potential studies were obtained and screened for inclusion by two teams of two independent reviewers.

Inclusion and exclusion criteria

The eligible study populations, interventions, comparators, outcomes, and study designs (PICOS) for the literature review were publications that: (a) were peer-reviewed, primary literature; (b) evaluated the adult human hippocampus or hippocampal subfields using 1.5 T magnetic resonance imaging (MRI) or greater for volume or 3 T MRI for structure; (c) assessed brain changes longitudinally for 1 year or longer; (d) included both healthy, cognitively normal, aged subjects and subjects with a diagnosis of AD and/or MCI; and (e) included subjects aged (on average) 65 years or older at baseline/first scan.

Studies were excluded if they failed to meet any of the inclusion criteria described above, as well as those that: (a) evaluated the hippocampus in dementias other than AD/MCI (e.g., Lewy body dementia, vascular dementia, frontotemporal dementia, tauopathy, Parkinson’s dementia) or Down’s syndrome with dementia; (b) included a mixed sample of different dementias; (c) evaluated changes in the hippocampus due to toxin exposure, head injury, ischemia, or any disease other than AD/MCI; or (d) assessed the effects of interventions or therapeutics. Narrative reviews, systematic reviews, meta-analyses, epidemiological studies, protocols, case studies, editorials and commentaries, retracted articles, theory or hypothesis papers, modeling or artificial intelligence papers, method/technology development or validation papers, conference abstracts/proceedings, doctoral dissertations, master’s theses, book chapters, and retracted publications were not included.

Study selection

All retrieved studies were assessed against the eligibility criteria. Primary screening of titles and abstracts was performed by two independent reviewers who reviewed each reference identified by the literature search to identify studies eligible for full text review. Any uncertainty regarding inclusion/exclusion decisions was resolved by consensus. For secondary screening of potentially relevant articles, full text articles and Supplementary material were obtained. Screening was performed by two teams of two independent reviewers. Any uncertainty regarding inclusion/exclusion decisions was resolved by consensus. The results of the study selection process are summarized in a PRISMA flowchart ( Figure 1 ).

Figure 1 . Search results.

Data extraction and synthesis

A standardized evidence data extraction template was developed in Microsoft Excel and populated with data extracted from the included studies. For each study, data were extracted from both the main study and Supplementary materials (when appropriate). All data were extracted, and quality checked against the original source article by a single reviewer. This systematic review synthesizes and summarizes the findings as they relate to hippocampal changes in people without cognitive impairment compared with those observed in MCI and in AD.

Risk of bias assessment

The risk of bias assessment and methodological quality assessment was conducted using the US National Heart, Lung, and Blood Institute 14-item checklist for observational cohort and cross-sectional studies that assesses study population, risk, data presentation and analysis, study design, and outcome ( National Institutes of Health, 2021 ). The quality assessment was performed by a single reviewer, with a quality check conducted by a second reviewer. The overall quality of eligible studies was determined using a scoring method previously described by Cotelli et al. (2020) , in which the number of affirmative responses to 14 quality assessment questions ( Supplementary Table S1 ) received one point and the sum of all responses was classified as follows: scores from 1 to 4 were rated as “poor,” 5–9 as “fair,” and 10–14 as “good.” A higher rating translated into a lower risk of bias.

The systematic search of the PubMed database yielded 357 articles ( Figure 1 ). In total, 115 studies passed the primary title and abstract screening criteria and were retrieved and reviewed in full ( Supplementary Tables S2, S3 ). Of these, 98 articles were excluded, with the most common reason for exclusion being MRI not longitudinal >1 year ( n  = 73; Figure 1 ). During data extraction, two additional studies were found to be unsuitable for the final systematic review [MRI not longitudinal >1 year ( n  = 1); lack of an aged control group ( n  = 1)]. The remaining 15 studies were included in the final systematic review ( Figure 1 ).

Study summary

The 15 included studies are detailed in Table 1 . Based on the inclusion criteria, all studies had longitudinal MRI obtained from cognitively unimpaired subjects and those with a diagnosis of AD and/or MCI. It is important to note that 12 of the 15 studies analyzed existing data that were obtained from the databases of the Alzheimer’s Disease Neuroimaging Initiative (ADNI, n  = 9), the Knight Alzheimer’s Disease Research Center ( n  = 1), the Oregon Aging and Alzheimer’s Disease Center at Oregon Health and Science University ( n  = 1), or the Mayo Clinic Alzheimer’s Disease Research Center and Alzheimer’s Disease Patient Registry ( n  = 1), and the other three studies were smaller observational studies.

Table 1 . Studies included in the systematic review.

The total sample sizes of the included studies ranged from 39 to 1,523 subjects. Overall, mean age of subjects was over 70 years of age. In general, scan intervals and follow-up were variable within samples and between studies; however, most studies had a follow-up period of two or more years and at least two scans per subject. The studies used 1.5 T MRI (n = 12), 3 T MRI (n = 1), or both (n = 2), and for the purpose of this systematic review, we focused on total hippocampus or hippocampal subfield volume and/or atrophy data. In all the included studies, cognitively normal-aged subjects were considered the control group.

Overall, there was large heterogeneity among these studies due to differences in study designs, measurements and methodologies to determine hippocampal changes, sample sizes, scan interval, and follow-up period, making direct comparisons difficult. For this reason, the results are presented below as summaries of each study.

Results of individual studies

Alzheimer’s disease neuroimaging initiative studies.

The following studies evaluated data from the ADNI database. ADNI enrolls participants between the ages of 55 and 90 years recruited from sites located in the United States and Canada. Participants undergo a series of initial tests that are repeated at intervals over subsequent years, including a clinical evaluation, neuropsychological tests, genetic testing, lumbar puncture, and MRI and positron emission tomography (PET) scans. Subjects are classified as normal subjects, MCI subjects and mild AD subjects. Normal subjects are defined as those with Mini-Mental State Examination (MMSE) scores between 24 and 30 (inclusive), a Clinical Dementia Rating (CDR) of 0, non-depressed, non-MCI, and nondemented. MCI subjects are defined as those with MMSE scores between 24 and 30 (inclusive), a memory complaint, have objective memory loss measured by education adjusted scores on Wechsler Memory Scale Logical Memory II, a CDR of 0.5, absence of significant levels of impairment in other cognitive domains, essentially preserved activities of daily living, and an absence of dementia. Mild AD subjects are defined as those with MMSE scores between 20 and 26 (inclusive), CDR of 0.5 or 1.0, and meet the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association criteria for probable AD (NINCDS-ADRDA) ( Alzheimer’s Disease Neuroimaging Protocol, 2016 ), which incorporates the use of biomarkers to determine different disease stages ( Jack Jr et al., 2011 ).

Andrawis et al. (2012) examined the effects of maternal history of dementia in 243 subjects with MCI, 96 subjects with AD, and 145 normal-aged control subjects from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI at baseline and 1-year follow-up. Overall, MCI subjects with positive maternal history of dementia had smaller hippocampal volumes at baseline and follow-up, and greater 12-month atrophy rates than subjects with negative maternal history. Although those without cognitive impairment and a positive maternal history/negative paternal history of dementia had smaller hippocampal volumes at baseline and follow-up compared to subjects with positive paternal history and maternal negative history of dementia, these differences were not statistically significant. A limitation of this study is the self-reported parental history of dementia.

Fiford et al. (2018) studied patterns of whole-brain and hippocampal atrophy in 339 subjects with MCI, 153 subjects with AD, and 191 without cognitive impairment from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI at baseline and at 6-month intervals, up to 36 months, atrophy rates were calculated based on longitudinal volume change. AD subjects had average atrophy rates of 14 mL/year for the whole brain and 0.2 mL/year for the hippocampus. Subjects with MCI had atrophy rates of 10 mL/year for the whole brain and 0.1 mL/year for the hippocampus, for apolipoprotein E (APOE) negative individuals. Subjects without cognitive impairment had average atrophy rates of 6 mL/year for the whole brain and 0.06 mL/year for the hippocampus, for APOE-negative individuals (APOE-positive individuals not reported). However, a significantly greater hippocampal atrophy rate was observed in older patients within the control group and in younger patients with AD. Limitations of this study include significantly different follow-up rates in AD vs. normal control subjects, and various methodological limitations, such as the fact that there was a small number of AD patients aged less than 65 years and all patients had memory problems associated with a late-onset phenotype.

Insel et al. (2015) estimated the association between cerebral spinal fluid (CSF) amyloid-β and regional brain atrophy in 183 subjects with MCI and 108 control subjects from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI at baseline and at 6-month intervals, up to 4 years. In MCI, periods of accelerated atrophy were evident in several brain regions, including the hippocampus, well before CSF levels of Aβ42 reached the threshold for “preclinical AD.” Additionally, although a substantial number of subjects with unimpaired cognition were above the threshold of amyloid-β positivity, excess accumulation of amyloid-β alone did not necessarily result in an immediate increase in atrophy rates and cognitive impairment. This could be due to latent factors such as the duration of exposure to amyloid-β pathology or concurrent co-pathologies such as Lewy body pathology and cardiovascular disease. These factors may contribute to an increased vulnerability of MCI subjects to the effects of amyloid-β, in contrast to controls. Overall, CSF levels of Aβ42 were associated with APOE4 positivity and Alzheimer’s Disease Assessment Scale-cognitive subscale (ADAS-cog) within both groups. Limitations of this study include various follow-up rates, limited Aβ42 data, and the fact that not all subjects had multiple MRI scans up to 4 years.

Jack et al. (2005) hypothesized that atrophy rate was associated with time to subsequent clinical diagnosis to a more impaired cognitive state in both cognitively unimpaired subjects ( n  = 91) and those with amnestic MCI (aMCI; n  = 72) from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI at baseline and 1- and 2-year follow-up. Rates of atrophy for subjects with MCI were greater than for those with unimpaired cognition, including in the hippocampus (−3.3 vs. −1.7 average annual % change). During follow-up, 39 subjects with MCI progressed to AD while 13 with unimpaired cognition developed MCI ( n  = 11) or AD ( n  = 2). For the subjects with unimpaired cognition, only larger ventricular annual percent volume change was associated with a higher risk of conversion. Limitations of this study include relatively short and varied years of patient follow-up.

Liu et al. (2021) correlated hippocampal subfield atrophy with CSF biomarkers and cognitive decline over the course of AD in 557 subjects with stable MCI, 304 subjects with AD, 241 subjects who progressed from MCI to AD, and 421 subjects with unimpaired cognition from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T or 3 T MRI at baseline and had, on average, 2.1 years between the first and last scan. Almost all hippocampal subfields showed an increase in percent atrophy rate per year (control < stable MCI < developed MCI < AD); the same pattern of atrophy severity was observed in the whole hippocampus. Compared with the whole hippocampus, the presubiculum and molecular layer of the dentate gyrus showed a greater atrophy rate in all four groups. In the subjects with stable MCI and those who progressed from MCI to AD, a decline in attention was associated with the atrophy rate of most of the subicular complex and CA regions. In incident MCI, presubiculum atrophy was associated with CSF tau levels and corresponded to the onset age of AD and a decline in attention. Limitations of this study include use of a mix of 1.5 T and 3 T MRI, various follow-up rates, and the fact that not all subjects had multiple MRI scans.

Lo et al. (2011) assessed the relationship between the longitudinal change of biomarkers (e.g., Aβ42 level in CSF) and hippocampal volume, as well as the presence of the APOE4 gene, on cognitive decline in 193 subjects with AD, 397 subjects with MCI, and 229 normal-aged control subjects from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI at baseline and 6- or 12-month intervals, up to 36 months. The rate of hippocampal atrophy was significantly slower in control subjects with normal cognition (−2.95 mm 3 /month) than in those with MCI (−5.52 mm 3 /month) or AD (−8.01 mm 3 /month). The Aβ42 level appeared to decrease faster in control subjects than in those with MCI or AD, although the differences did not reach statistical significance. In normal control subjects, APOE4 status was associated with Aβ42 in CSF but not baseline hippocampal volume, and in subjects with MCI and AD, APOE4 was associated with accelerated hippocampal atrophy. For subjects with MCI, changes on the ADAS-cog were associated with a decrease in the Aβ42 level in the CSF and hippocampal volume. Limitations of this study include longer follow-up rates for normal control or MCI subjects than for those with AD and the varying number of repeated measures for longitudinal analyses across different biomarkers and diagnostic groups.

Mattsson et al. (2014) sought to determine whether the development of amyloid-β pathology is related to increased regional atrophy in the brains of 47 control subjects ( n  = 13, amyloid-β- stable; n  = 13, amyloid-β- declining; n  = 21, amyloid-β+) and 15 subjects with AD from the ADNI database ( Table 1 ). All subjects underwent repeated CSF Aβ42 measurements and 1.5 T MRI at baseline and at 6-, 12-, 24-, 36-, and 48-months. At baseline, amyloid-β- stable control subjects had smaller overall, hippocampus, amygdala, temporal, control, and parietal volumes compared with amyloid-β+ normal subjects. In addition, compared with amyloid-β- stable normal subjects, amyloid-β- declining control subjects had increased atrophy rates in overall, frontal, and parietal regions, and amyloid-β+ control subjects had increased atrophy rates in overall, amygdala, temporal, cingulate, frontal, and parietal regions. The AD amyloid-β+ subjects had increased atrophy rates in all regions compared with control amyloid-β- stable normal subjects and had increased atrophy rates in overall, hippocampus, temporal, and cingulate regions compared with amyloid-β+ normal subjects, suggesting that atrophy may accelerate in the hippocampus, temporal, and cingulate regions as subjects progress to dementia. Limitations of this study include a small sample size and the fact that not all subjects had CSF and/or MRI at all timepoints.

Nosheny et al. (2015) evaluated factors that contributed to hippocampal atrophy rate in 359 MCI subjects and 208 clinically normal-aged subjects from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI over 4 years. In control subjects, only increased amyloid-β levels in the CSF were significantly associated with hippocampal atrophy rate when adjusting for age, gender, and APOE4 genotype. In MCI subjects, both amyloid-β levels and APOE4+ genotype were significantly associated with hippocampal atrophy rate. Rates of hippocampal atrophy were significant in amyloid-β+ and amyloid-β- normal subgroups for both control and MCI, with amyloid-β+ subjects having a higher hippocampal atrophy rate. In the MCI only or the combined cohort (controls+MCI), there was a significant interaction between amyloid-β status and age, with a stronger association between age and hippocampal atrophy rate in the amyloid-β- subjects indicating that age had a significantly higher association with hippocampal atrophy in amyloid-β- participants than in amyloid-β+ participants in MCI. Although the presence of amyloid-β was a major predictor of hippocampal atrophy rate, in most cases, the hippocampal atrophy rate was not associated with the presence of amyloid-β and thought to be a consequence of aging and other unknown factors. Limitations of this study include a significantly greater number of male than female subjects with MCI compared to normal controls, and the fact that CSF amyloid-β samples were taken before the initial volume measurements.

Skup et al. (2011) studied whether there were gender differences in gray matter atrophy patterns over time in 197 subjects with AD, 266 subjects with aMCI (defined as MCI with memory loss as the predominant symptom), and 224 control subjects from the ADNI database ( Table 1 ). All subjects were scanned using 1.5 T MRI over 2 (AD group) and 3 years (aMCI and control group). Validation studies showed that AD and subjects with aMCI had decreased hippocampal volume over time compared with normal control subjects. Male and female subjects with AD and aMCI showed different patterns of decline over time compared with normal control subjects in bilateral precuneus, bilateral caudate nucleus, right entorhinal gyrus, bilateral thalamus, bilateral middle temporal gyrus, left insula, and right amygdala. Limitations of this study include longer follow-up for subjects with normal control or MCI than those with AD and various methodological limitations such as the over-representation of males among aMCI patients and the utilization of data from stable AD subjects who were relatively early in their cognitive decline as well as from individuals with stable aMCI who were not separated into subtypes.

Other studies

Li et al. (2011) investigated the gray matter changes in AD progression in 64 subjects with AD and 86 subjects with unimpaired cognition, including 14 who developed dementia during the course of the study, from the Open Access Series of Imaging Studies (OASIS) dataset generated across several projects through the Washington University School of Medicine Knight Alzheimer Disease Research Center ( Table 1 ). The AD subjects were clinically diagnosed with very mild to moderate AD (CDR = 0.5, very mild dementia; CDR = 1, mild dementia; or CDR = 2, moderate dementia). All subjects were scanned using 1.5 T MRI at baseline and at least 1-year follow-up. Initial gray matter deficits encompassed the hippocampus and entorhinal cortex regions, with development of increasing pathology in other regions over time. Results suggested faster atrophy rates in the hippocampus over several years near illness onset. In general, there was variation across subjects with AD in terms of yearly rate of gray matter atrophy for both the hippocampus and medial temporal gyrus, but it was typically 1% for the hippocampus and 0.5% for medial temporal gyrus, which was, respectively, 2x and 5x greater than the atrophy rate in normal control subjects. However, the atrophy rate was significantly higher in the medial temporal gyrus for the converter group. Limitations of this study include differing time intervals between the first and second time points for all subjects, and the utilization of combined data from AD subjects and subjects who developed dementia during the course of the study.

Silbert et al. (2003) investigated whether changes in antemortem brain volume are predictive of subsequent AD pathology in 24 cognitively impaired subjects and 15 normal-aged control subjects from the Oregon Aging and Alzheimer’s Disease Center at Oregon Health and Science University ( Table 1 ). Subjects were categorized according to their clinical dementia stage based on the last CDR as nondemented (CDR = 0.0) or demented (CDR = 0.5). Neuropathologic diagnosis of AD was determined using regional postmortem measures of neurofibrillary tangles. All subjects were followed on average for 5.8 years and scanned using 1.5 T MRI, with an average interscan interval of 4.1 years. In subjects with cognitive impairment, there was a relationship between degree of hippocampal neurofibrillary tangle burden and total hippocampal volume prior to death. However, no such relationship was observed between the amount of neurofibrillary tangle burden and the rate of hippocampal volume change. In normal control subjects, no significant relationship was found between hippocampal neurofibrillary tangle burden and hippocampal volume prior to death or rate of hippocampal volume change over time. In cognitively impaired subjects, the average rate of ventricular volume increase was 5.5 cc/year, while the average rate of central nervous system volume decrease was −17.9 cc/year. In normal control subjects, the average rate of ventricular volume increase was 3.3 cc/year, while the average rate of total brain volume decrease was −1.8 cc/year. Limitations of this study include various follow-up rates, a small sample size, the inclusion of two subjects with mixed AD/vascular pathology, and the fact that not all subjects had multiple MRI scans.

Tarawneh et al. (2015) studied the usefulness of various CSF markers (e.g., Aβ42, p-tau) in predicting rates of whole-brain neurodegeneration and whole-brain atrophy in 23 subjects with mild AD and 64 cognitively normal-aged control subjects from The Charles F. and Joanne Knight Alzheimer’s Disease Research Center at Washington University School of Medicine ( Table 1 ). All individuals in the AD cohort had a clinical diagnosis of very mild symptomatic AD (CDR = 0.5) at the baseline assessment. APOE genotypes were obtained. All subjects had baseline CSF biomarker measurements and were scanned using 1.5 T or 3 T MRI at baseline and 2- to 3-year follow-up. At baseline, average hippocampal volume for normal control subjects (7,438 mm 3 ) significantly differed from subjects with AD (6,310 mm 3 ). The average adjusted rate of atrophy in normal control subjects was −0.003 points per year for normalized whole-brain volume (−0.4% annual change from baseline) and −100 mm 3 per year for hippocampal volume (−1.3% annual change from baseline), whereas the adjusted rate of atrophy in AD was −0.007 points per year for normalized whole-brain volume (−0.9% annual change from baseline) and −271 mm 3 per year for hippocampal volume (−4.3% annual change from baseline). In subjects with AD, baseline levels of certain CSF markers (VILIP-1, tau, p-tau) predicted whole-brain and hippocampal atrophy. After adjusting for age, sex, imaging system type, and APOE 4 genotype, cognitively normal control subjects with CSF markers in the upper tercile had higher rates of whole-brain and hippocampal atrophy compared to those with lower levels of CSF markers. In this subset of normal control subjects, CSF biomarker levels and rates of whole-brain and regional atrophy were similar to subjects with AD. Limitations of this study include a relatively short and varied follow-up, a small sample size, and the use of a mix of 1.5 T and 3 T for structural MRI.

Wang et al. (2009) researched hippocampal atrophy rates in 39 subjects with stable aMCI, 19 subjects with progressive aMCI, and 20 control subjects from Taipei Veterans General Hospital ( Table 1 ). Clinical diagnoses were based on medical history, plus clinical and neuropsychological assessment. Subjects diagnosed with MCI fulfilled Petersen’s criteria of aMCI, meaning they were nondemented, had subjective memory complaints, objective memory impairment, normal general cognitive function, intact daily living activities, and a CDR score of 0.5. All subjects were scanned using 1.5 T MRI at baseline and at 12-month intervals, up to 2 years. At baseline, bilateral hippocampal volumes differed significantly between the groups (normal control subjects > stable MCI > progressive MCI). During follow-up, subjects with progressive MCI had significantly greater atrophy rates in both the right and left hippocampus compared with normal controls, and greater atrophy in the right, but not left hippocampus, compared to subjects with stable MCI. In subjects with MCI, there was a significant correlation between decline in memory test scores and hippocampal atrophy rates. Limitations of this study include a small sample size, the inclusion of more male than female subjects, and a variable follow-up period.

Whitwell et al. (2007) assessed the progression of cerebral atrophy during conversion to AD in 33 subjects with aMCI converting to AD and 33 control subjects from the Mayo Clinic Alzheimer’s Disease Research Center and Alzheimer’s Disease Patient Registry ( Table 1 ). Individuals were diagnosed as having aMCI if they met the following criteria: (1) memory complaint, preferably corroborated by an informant; (2) memory impairment for age; (3) essentially normal general cognitive function; (4) generally preserved activities of daily living; (5) not demented. All subjects were scanned using 1.5 T MRI three times, approximately 3 years before conversion from aMCI to AD, approximately 1 year before conversion, and at the time of conversion. 3 years prior to conversion from aMCI to AD, gray matter loss was primarily observed in the medial temporal lobe, including the bilateral anterior hippocampus. The magnitude of cerebral atrophy progressed by the time the subjects were 1 year prior to conversion and extended to include the posterior temporal lobe and entire hippocampus. By the time subjects had a clinical diagnosis of AD, the pattern of gray matter atrophy had become more widespread, with severe gray matter loss throughout the temporal lobes, in the temporoparietal association neocortex, and in the frontal lobes. Overall, the hippocampus showed progressive atrophy throughout the disease course, with the severity of volume loss detected on MRI increasing at each time-point measured. Limitations of this study include a small sample size and a variable follow-up period.

Quality of the included studies

The risk of bias rating was “good” for nine of the 14 included studies, while a “fair” risk of bias rating was obtained for the remaining five studies ( Supplementary Table S1 ). These results indicated a low overall risk of bias in the included evidence, owning to the well-defined methodologies and use of robust databases with longitudinal data. A common limitation observed in the evidence was the lack of sample size justification, which is inherent in observational studies due to their exploratory nature.

In this systematic review, we summarized the evidence related to hippocampal changes detected by longitudinal MRI in people with no cognitive impairment, those with MCI and those with AD populations from 15 studies published between 2003 and 2021, including nine studies from ADNI. Despite the large heterogeneity among these studies due to differences in study designs, methodologies, sample sizes, scan intervals, and follow-up period, this systematic review provides further support for the view that hippocampal changes, specifically decreased volume and increased rate of atrophy, occur during aging, MCI and AD, with greater changes in the latter two.

All studies included cognitively unimpaired, aged subjects and those with MCI and/or AD. Several of the studies observed that the hippocampus and hippocampal subfields change over time, with changes in AD greater than changes in MCI, and changes in MCI greater than changes prior to cognitive impairment (e.g., Jack et al., 2005 ; Wang et al., 2009 ; Lo et al., 2011 ; Skup et al., 2011 ; Fiford et al., 2018 ; Liu et al., 2021 ). In general, the hippocampus showed progressive atrophy near the onset of AD ( Li et al., 2011 ) and throughout the disease course ( Whitwell et al., 2007 ), and was associated with cognitive decline ( Lo et al., 2011 ;). In subjects with dementia, a relationship was observed between the degree of hippocampal neurofibrillary tangle burden and total hippocampal volume prior to death ( Silbert et al., 2003 ). Finally, maternal history of dementia had a significant effect on hippocampal atrophy in MCI and AD and was non-significantly associated with smaller hippocampal volumes in cognitively unimpaired controls ( Andrawis et al., 2012 ).

Various hippocampus outcomes were reported for those without cognitive impairment. In particular, the percent yearly atrophy rate in aged unimpaired subjects was reported at approximately 1% (e.g., Jack et al., 2005 ; Li et al., 2011 ; Tarawneh et al., 2015 ; Liu et al., 2021 ) and older age at baseline was associated with hippocampal atrophy rate ( Fiford et al., 2018 ). In multiple studies, amyloid-β status ( Mattsson et al., 2014 ) or amyloid-β levels ( Nosheny et al., 2015 ) were associated with hippocampal atrophy rate. However, it was also shown that in control subjects, excess accumulation of amyloid-β beyond the clinical threshold for amyloid-β positivity did not necessarily result in an immediate increase in atrophy rates and cognitive impairment ( Insel et al., 2015 ). Notably, Nosheny et al., 2015 concluded that the presence of brain amyloid is a major predictor of hippocampal atrophy rate in older adults, but that in most cases, hippocampal atrophy rate in older adult subjects with unimpaired cognition or MCI is not associated with the presence of amyloid-β and is likely to be a consequence of aging and other unknown factors.

Finally, we are aware of at least one study related to hippocampal changes in cognitively unimpaired subjects published since the literature search for this systematic review was conducted and was therefore not included above ( Huang et al., 2023 ). The results reported by Huang et al. (2023) provide further support that hippocampal atrophy observed in patients with AD and MCI is faster than atrophy during normal aging.

The findings from the studies included in this review support the view that the mechanisms of hippocampal atrophy resulting in synaptic damage and neuronal loss are likely shared between AD and healthy aging ( Crews and Masliah, 2010 ). The proposed key stressors in this process are oxidative stress caused by free radicals and inflammation ( Kao et al., 2020 ; Zia et al., 2021 ; Andronie-Cioara et al., 2023 ; Plascencia-Villa and Perry, 2023 ), both rapidly affecting the hippocampus, known for its high plasticity, and therefore its vulnerability toward stressors ( McEwen, 1994 ).

The strength of this systematic review is that it was guided by the PRISMA methodology. However, a critical appraisal of the included studies to qualitatively assess the robustness of individual study methodologies and their reporting standards was not performed.

Furthermore, due to the restrictive nature of the search criteria, the search may have missed publications that looked at longitudinal hippocampal changes in cognitively unimpaired aging or individuals with (non-clinical) subjective cognitive decline as the primary endpoint (in the absence of an AD group). Specifically, in the studies that met the inclusion criteria, normal aging subjects were considered the control group. Thus, hippocampal changes in normal aging were not the focus of the studies.

It is also worth noting that nine of the publications used existing longitudinal data from the ADNI database across overlapping data collection timeframes. It is likely that the same patient pool might have been investigated across multiple publications. Furthermore, many of the publications did not report the specific timeframe of data collection. Therefore, the scope of data overlap across these studies is unclear, and an overrepresentation of evidence from these studies cannot be ruled out. Thus, we cannot consider these studies as being independent.

Finally, the publications used different imaging strengths, measurements, and methodologies to determine hippocampal changes, making direct comparisons of outcomes difficult and inappropriate.

Patterns of brain volume decline have been shown in patients treated with anti-amyloid therapies and therapeutic antibodies. Donanemab and lecanemab have been shown to increase ventricular volume and decrease brain volume, though hippocampal volume loss due to donanemab resembled that of placebo ( Lowe et al., 2021 ; Swanson et al., 2021 ). In addition, the specific multinutrient intervention containing Fortasyn Connect™ (Souvenaid™, Nutricia, N.V., Zoetermeer, Netherlands) significantly slowed hippocampal volume and whole brain volume decline in a randomized controlled trial with 311 prodromal AD patients ( Soininen et al., 2021 ). The results highlight the importance of hippocampal changes across the continuum from normal aging to AD.

The findings of this systematic review suggest that hippocampal changes observed prior to the onset of cognitive impairment parallel those found in MCI and AD. In addition, the published literature included here indicates that the rate of hippocampal decline and extent of volume loss between those without cognitive impairment, MCI, and AD is quantitative rather than qualitative. The yearly hippocampal atrophy rate is approximately 1% in aging subjects with unimpaired cognition compared with approximately 3–5% in subjects with MCI and AD. This suggests that hippocampal atrophy, like cognitive function and AD pathology, is on a continuum and that the disease status, i.e., MCI and dementia, represents a cut point along a single disease process.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary material , further inquiries can be directed to the corresponding author/s.

Author contributions

MW: Conceptualization, Writing – review & editing. DB: Writing – review & editing. TaR: Methodology, Writing – review & editing. GP: Conceptualization, Writing – review & editing. ToR: Conceptualization, Writing – review & editing.

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. Editorial assistance for the development of the manuscript was funded by Danone.

Acknowledgments

Editorial assistance for the preparation of the manuscript was provided by Abegale Templar of mXm Medical Communications. We sincerely thank Lumanity for conducting the systematic review.

Conflict of interest

MW receives a paid speakers fee and hononaria for expert advice to Nutricia, GSK, MSD, Roche, Biogen, Eisai, Novo Nordisk, Actinogen Medical, Moderna, and Pfizer. DB served as a paid consultant to Nutricia for the manuscript; DB was United States Principal Investigator for Nutricia’s S-Connect study, and currently serves on a Data and Safety Monitoring Committee for a Phase I clinical trial by AbbVie. DB also consults for B4X, conducts a study funded by Neurovision, serves on a scientific advisory board for Vigorous Minds, and receives research support from the NIH and State of Illinois. TaR is supported by grants from NIH and Florida Department of Health. GP is part of the Scientific Advisory Board in Synaptogenix and Nervgen. ToR is an employee of Nutricia Specialized Nutrition.

The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Publisher’s note

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Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fnagi.2024.1390574/full#supplementary-material

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Keywords: Alzheimer’s disease, cognitive aging, hippocampal atrophy, hippocampal volume, mild cognitive impairment, systematic literature review

Citation: Woodward M, Bennett DA, Rundek T, Perry G and Rudka T (2024) The relationship between hippocampal changes in healthy aging and Alzheimer’s disease: a systematic literature review. Front. Aging Neurosci . 16:1390574. doi: 10.3389/fnagi.2024.1390574

Received: 23 February 2024; Accepted: 05 August 2024; Published: 15 August 2024.

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Copyright © 2024 Woodward, Bennett, Rundek, Perry and Rudka. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Michael Woodward, [email protected]

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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Umbrella review on the relationship between vitamin d levels and cancer.

1. Introduction

2. materials and methods, 3.1. breast cancer, 3.2. prostate cancer, 3.3. pancreatic cancer, 3.4. colorectal cancer, 3.5. lung cancer, 3.6. methodological quality, 4. discussion, 5. conclusions, author contributions, conflicts of interest.

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Share and Cite

Schömann-Finck, M.; Reichrath, J. Umbrella Review on the Relationship between Vitamin D Levels and Cancer. Nutrients 2024 , 16 , 2720. https://doi.org/10.3390/nu16162720

Schömann-Finck M, Reichrath J. Umbrella Review on the Relationship between Vitamin D Levels and Cancer. Nutrients . 2024; 16(16):2720. https://doi.org/10.3390/nu16162720

Schömann-Finck, Matthias, and Jörg Reichrath. 2024. "Umbrella Review on the Relationship between Vitamin D Levels and Cancer" Nutrients 16, no. 16: 2720. https://doi.org/10.3390/nu16162720

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