# Analysis of case-control studies

In a case-control study there is a group of subjects with the disease **(cases)** and a sample of subjects without the disease **(controls)**. The exposure status for each subject is then determined and compared in the two groups.

Please note that it is not possible to estimate the incidence of disease from a case-control study unless the study is population based and all cases in a defined population are obtained.

The odds ratio (OR) is a measure of association for a case-control study. It tells us how much higher the odds of exposure is amongst cases of a disease compared with controls. The odds ratio compares the odds of exposure to the factor of interest among cases to the odds of exposure to the factor among controls.

Watch the video on analysis of case-control studies below.