Fig. 1.

The self-controlled cohort study design. An example studying the association between one medication and incident dementia by including all patients who were exposed to the medication. It shows incident dementia occurring during the time a patient was on treatment (patient 1), not occurring in patient's history (patient 2), occurring outside of the observation windows and therefore not counted in either period (patient 3) and occurring during the unexposed control period (patient N). This approach was repeated for all 2181 medications identified in the database.