7.2.1.2 Case-control studies

Case-control studies select participants based on presence of disease or a specific condition, and look for prior exposures that may have led to the disease or outcome developing. In this study design, those with the disease/outcome (cases) are matched with comparable individuals who do not have the disease (controls), and both groups are studied to determine if any differences in characteristics or past exposures exist. Case control studies have an advantage over cohort studies, particularly when investigating rare diseases, because of fewer costs associated with recruiting participants (usually less). In addition, the issue of “drop out” or “loss to follow up” of participants as seen in cohort studies does not arise in case-control studies.