An observational study that compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls). It looks back retrospectively to compare
how frequently the exposure to a risk factor is present in each group. This allows the investigator to decide upon the relationship between the risk
factor and the disease.
Case-control studies are observational because there is no intervention and no attempt is made to alter the course of the disease. The goal is to retrospectively decide upon the exposure to the risk factor of interest from each of the two groups of individuals: cases and controls. These studies are designed to estimate odds or chances.
Case-control studies are also known as ‘retrospective studies’ and ‘case-referent studies’.