What is a case-control study?
A case-control study is an analytical study which compares individuals who have a specific disease ("cases") with a group of individuals without the disease ("controls"). The proportion of each group having a history of a particular exposure or characteristic of interest is then compared. An association between the hypothesized exposure and the disease being studied will be reflected in a greater proportion of the cases being exposed. It is advantageous for the controls to come from the same population from which the cases were derived, to reduce the chance that some other difference between the groups is accounting for the difference in the exposure that is under investigation. A case-control study generally depends on the collection of retrospective data, thus introducing the possibility of recall bias. Recall bias is the tendency of subjects to report events in a manner that is different between the two groups studied. People who have a disease may be more likely to remember exposures more readily than those without the disease. The opportunities to effectively use case-control studies may expand as new ways of characterizing exposure through the use of biologic markers of exposure are developed, which would reduce the problem of recall bias.