New medical research is published constantly, and even the most diligent health care providers have difficulty staying on top of every new study that may affect their area of practice. Facing a medical issue often motivates many of us to find and understand the most current research. Here’s how to become an informed reader.
Where to Find Research Studies
Nearly all research published in peer-reviewed health journals can be found by searching MEDLINE, a database available through PubMed. PubMed provides study abstracts (structured summaries providing key information about the design and main results of the research) at no charge. There may be a fee, however, for access to a full article.
Another excellent source of research is the Cochrane Database of Reviews. The Cochrane Collaboration creates systematic reviews of the best research about the safety and effectiveness of health and medical interventions. Abstracts of the reviews and plain-language summaries are available online for free.
Increasingly, people can obtain access to research studies and other professional publications such as clinical guidelines through open access journals, through public access articles, or by requesting articles from a library. One benefit of using the library is that a trained librarian may be able to search for you or show you how to make the best use of databases.
Some hospitals or treatment centers have libraries and services to help patients learn more about their condition. State universities with medical schools are often required to make their medical libraries open to the public, and the medical librarians at these institutions can offer expert assistance. You might also be able to ask a friend at an academic institution (with free access to medical journals) to help you retrieve specific articles.
READING A RESEARCH STUDY
Reading research can be daunting at first, and understanding it takes practice. Once you read a few studies you will notice that they are organized predictably into several sections.
A research paper begins with an abstract that summarizes the study’s methods and results and the researchers’ conclusions.
The full article begins with an introduction that frames the research problem and reviews the existing research in the area.
The researchers should then include a methods section that explains exactly how they conducted their study, including how they recruited participants, what intervention or procedure was tested, and how data were collected and processed.
This is followed by a results section, which often includes tables, charts, or graphs. If the study is comparing two or more groups, the researchers will state whether differences in outcomes among those groups are statistically significant, meaning they are unlikely to have occurred by chance and are therefore likely to be associated with the intervention or behavior being studied.
The article will end with a discussion section that reviews the major findings, discusses the strengths and limitations of the study, and makes recommendations for further research or changes in practice.
It’s important to focus on the methods and results sections, as the abstract and discussion section often focus on the authors’ interpretations or opinions rather than on the actual findings. In some cases, the authors’ statements in these sections may not be supported by the information in the methods and results sections.
Types of Research Studies
When seeking out health information, it’s common to read and hear many competing claims and statistics. Understanding the different types of research studies behind these numbers can help us evaluate their results and make informed health care decisions.
There are three major types of research studies:
In a cohort study, researchers follow a group, or cohort, of people for a period of time. The researchers determine whether the individuals experience a particular exposure, such as whether they take a drug or supplement, exercise, smoke, or eat certain foods.
The researchers follow all the people in the cohort (both those who do and those who do not experience the exposure of interest) to see whether they experience a particular outcome (for example, development of a certain disease). The researchers then calculate the risk of developing the outcome (called the incidence rate).
Cohort studies can detect relationships between exposure and outcome but they cannot definitively claim that the exposure or treatment causes the outcome.
In a case-control study, researchers investigate two groups, one that has a certain outcome, such as a disease, and one that does not. The group with the disease is called the case group, and the others are known as the control or comparison group.
Researchers determine whether or not the people experienced specific exposures of interest (such as diet or exercise). Identifying case and control groups based on outcome is the hallmark of case-control studies, which are common when the outcome of interest is rare (such as certain cancers) or when it is not possible for practical or ethical reasons to assign different groups to different treatments (such as smoking or experiencing abuse).
Like cohort studies, case-control studies show a relationship between treatment and outcome but they cannot definitively claim that the relationship is causal.
Randomized Controlled Trial
In a randomized controlled trial, researchers recruit people to participate in a study. Once they agree to participate, they are assigned randomly to receive either the treatment being tested or a placebo (such as a sugar pill). The study is called randomized because there is no rhyme or reason to whether a person ends up getting the treatment or the placebo.
If neither the people participating in the study nor the health professionals working with them know which group a person is in, the study is called double-blind. The placebo helps with the blinding, so that the individual and his or her doctor can’t tell by looking at the pill whether it’s an active treatment or a sugar pill.
Randomized, double-blind placebo-controlled trials are thought of as the gold standard in research. They attempt to test whether treatment X causes outcome Y, and they can come the closest to claiming causation because of the blinding, the randomization, and the use of a placebo. The idea is that everything is held constant, except whether an individual is getting the placebo or the actual treatment.
Understanding Relative vs. Absolute Risk
Statistics about health can be confusing because risk can be measured in different ways.
Risk indicates whether or not a treatment or behavior (an exposure) is associated with an increased likelihood of developing a disease or condition (an outcome).
Relative risk is an indicator of the strength of the association between exposure and outcome. It is used to assess the importance of a particular factor or treatment in the development of a disease or condition.
Relative risk is often expressed as a percentage. For example, a study might conclude that women who took a specific medicine had, on average, a 25 percent decreased risk of developing a particular disease than women who did not take the drug. Relative risk is always an average for a group.
Absolute risk describes the effect of an exposure on an outcome in the general population (as opposed to comparing specific groups). In the population overall, how harmful is an exposure? What is the likelihood of developing a particular condition?Absolute risk provides answers to these questions.
For example, women in a certain country or city might have a 1 in 10 chance of developing a certain condition during their lifetimes. (This would be the same as a risk of 10 percent.) Like relative risk, absolute risk estimates represent averages for a population, not the proscribed fate of any individual.
Sometimes studies report what sound like dramatic changes, for example a 50 percent decrease in risk for developing a certain disease. But if this is a decrease in the relative risk, and the absolute risk of developing the disease is small, the number of women affected will be low.
For example, if the relative risk of developing a disease is cut in half by taking a certain drug, but only one in 100,000 women who do not take the medicine develop that disease each year, only one in 200,000 women per year would avoid developing the disease if the whole group took the medicine — and all of the other women would be at risk of experiencing its unwanted side effects.
Understanding what research results can tell us about our risk of developing a certain condition or disease is an important part of making health care decisions. It’s also important to remember that there is enormous variation among individuals and that our decisions are informed by our values and preferences as well as scientific evidence.