As a professor of Epidemiology, my primary goal is to teach my students how to read, critically analyze, and apply the results of an epidemiological study to create healthy communities. I want to empower my students to read research papers from beginning to end (not just the Abstract and definitely not skipping the Methods section). I want them to confidently read the literature, determine for themselves the strengths and limitations of the study, and be able to communicate the findings and any applications of those findings to a group of community members without any knowledge of epidemiology.
And I want to invite all of you into my classroom (so to speak). I want to provide you with a guide to reading the epidemiological research and the opportunity to read, discuss, and apply the findings of epidemiological studies with me.
Together — with improved literacy and the ability to see the strengths and limitations that are inherent in every study — we can fight misinformation, spot disinformation, craft strategies to improve health, and create healthy communities.
Are you ready?
Do you want to learn how to read, analyze, and apply the epidemiological literature?
Let’s get started… (if you missed one of the previous posts, start here — Rule #1)
As discussed in part #3 of this series — The Canon of Epidemiology — the authors of an epidemiological research paper will use the final sentence (maybe two) in the Introduction section of their paper to clearly articulate the purpose or objective of their research.
Following the Introduction (and a clear articulation of the purpose/objective of the paper) is the METHODS section. This section has two main purposes. The first is to provide enough information to enable the reader (YOU) to judge the validity and generalizability of the study results. Second, it allows other researchers to repeat the study to replicate the findings.
Quick vocabulary check — in epidemiology, when we use the terms validity and generalizability here’s what we mean…
VALIDITY is a lack of systematic error or bias. If we are conducting a study comparing individuals with cancer to those without, a valid way of measuring cancer would be through clinical diagnosis (a physician's diagnosis or medical records used to determine if a participant does or does not have cancer). An invalid or biased way of measuring cancer would be to ask individuals who have never been to a physician, have never been screened for cancer, or may not know what cancer is if they “think” they have cancer.
In this example, a valid study would ensure that individuals are classified as having or not having cancer with accuracy; and that there is no (or little) misclassification of cancer status in the study.GENERALIZABILITY is the degree to which the results of a study may apply or be relevant to populations or groups that did not participate in the study.
For the results of a study to be generalizable, the study first needs to be valid. If the study lacks validity, it cannot be generalizable to a larger population.
In every methods section, you should be looking for a description of who the participants of the study were. This is important because we are looking to take the results from that sample and apply it to a larger population. With the description of the study sample, clues about the validity and generalizability of the study are presented.
When thinking about the generalizability of a study, it is good to be curious.
Ask questions such as — where did the study take place & is that sample generalizability to me? when did the study take place & is it relevant to me today (or in the future)? is the sample similar to me and my community in terms of health status, age, access to healthcare, health insurance, exposure to specific diseases or risk factors?
The Methods section should also provide you with a road map for interpreting the results. Specifically, the Methods section should outline the design of the study. Were cases (those with disease) compared to controls (those without disease)? Or did the researchers compare individuals with a certain exposure — cigarette smoke — to those who do not have that exposure (or those who received a vaccine vs. those who did not)? Or did the researchers conduct an online survey where they gathered lots and lots of data about multiple diseases, lots of risk factors, and a host of environmental exposures — and they are trying to make sense of a lot of data collected at one point in time through a survey?
The design of the study will help you determine how the results will be presented and what comparisons will be made in the results section.
Similarly, the Methods section should list what data (aka the variables) was collected and how during the study. There should also be a clear description of how the data were analyzed and what statistical tests were used. This information will serve to guide you as you read through the results of the study.
Sidebar — next week we will be covering statistics. Be sure you are subscribed…
You do not want to miss my primer on understanding statistics.
In essence, the Methods section is your roadmap. It bridges the spaces between the study’s objective (as stated in the Introduction) and the results. It provides key landmarks — so to speak — highlighting the sample, study design, data that was collected, and how the data was analyzed. Ultimately, the methods provide you with the information you need to determine if a study is valid and if the results can be generalized to a population larger than the sample.
That’s it… that is a summary of how to navigate the Methods section of an epidemiological paper.
Next Tuesday we’ll move on to Statistics…
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Do you have questions about the the Methods section? or validity? generalizability?
Or would you like me to share a homework assignment with you? Leave me a comment (like “sign me up” or “send the homework now”) and your email address. I’ll be sure to include an answer key!
Epi(demiology) Matters is written by Dr. Becky Dawson, PhD MPH — an epidemiologist, teacher, mom, wife, and dedicated yogi. She is a tenured professor at Allegheny College, Research Director at a community hospital, and an exclusive contributor (all things health & medicine) at Erie News Now (NBC/CBS). Her goal is to create healthy communities for all. She writes Epi Matters — first & foremost because epidemiology does matter (to all of us) and she hopes that each post will help to educate and empower readers to be healthy and create healthy communities.
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