What is a research study?
In an experimental research study, participants are asked to take a particular medication, do a particular activity (such as exercise for 30 minutes 4 times a week), or undergo a particular treatment. The medication, activity, or treatment is known as an intervention. Over time, the researchers record what happens to the participants undergoing the intervention.
In most studies, participants receiving the intervention are compared with a control group, another group of study participants who are not undergoing the intervention. This kind of study is known as a controlled study. If the trial involves a drug, members of the control group may be given a placebo, a dummy pill that does not actually contain any medication. In some studies, both groups of patients receive an intervention — for example, when two different treatments are compared, such as angioplasty and bypass surgery. Researchers also try to ensure that the women in each group are similar in age, health, and lifestyle so that any differences between the two groups can be attributed to the intervention.
What is an observational study?
Observational studies follow a woman's medical and lifestyle practices but do not intervene. Investigators only observe and record naturally occurring events. Such studies can uncover possible relationships between various factors and health or illness. Those factors include population traits, ethnicity, genetic attributes, and behaviors. For example, it has been found that people who smoke have a higher chance of developing lung cancer, while people who drink moderately are at a lower risk for developing heart disease.
Researchers can also track women who do and do not take a certain type of drug. The results may show that the users of the drug have fewer heart attacks. But the results of observational studies, unlike studies that randomly assign women to take a drug or a dummy pill, cannot conclude that the drug reduces the risk of heart disease. Other factors may have played a part. Women who take the drug may have better access to health care or may be more likely to follow a healthy lifestyle. Observational studies can only show associations.
What is the difference between retrospective and prospective studies?
A retrospective study looks back at what happened to a group of people in the past. For example, researchers may look back through women's medical records or ask women to recall what they ate or what they did during a defined period of time. These studies are limited because people may not remember the details of what they ate, drank, or took. Another factor is that people who develop a disease or have a heart attack may be more likely to recall medications or diet because they are anxious to find an explanation for their illness. These studies are therefore used mainly to suggest areas for future research.
In a prospective study, researchers follow participants forward in time for weeks, months, or years and record what happens to them. Because these studies do not rely on reconstruction of past events, they are generally considered to produce more reliable results than retrospective studies.
What is a case-control study?
A case-control study is a type of observational study. Researchers identify two groups — one group comprises people who already have a specific condition, such as heart disease or diabetes, and one group of people who do not. They then compare the two groups to see if any factor was more prevalent in the past history of one group compared to the other (for example certain diet or lifestyle characteristics).
Case-control studies can be prone to inaccuracy because, like retrospective studies, they gather information about the past. This is a concern for a few reasons. First, it can be difficult for people to accurately remember specifics, especially when it comes to things like diet. Second, a person's memory may actually be biased by the fact that case-control studies gather information after an event, such as a heart attack or a diagnosis of diabetes, has happened. If you had a heart attack, you may be more likely to remember past details because you are anxious to find a cause. Third, it is difficult to prove that one factor necessarily caused the other.