Nested case-control studies

The association between suicide and the use of calcium channel blockers in people with hypertension was investigated using a nested case-control study design.1 Data were taken from the general practice research database, a computerised database of anonymised longitudinal medical records collected prospectively in primary care. The cohort of people with records between January 1991 and August 1998 was used. At the end of data collection, 38 people who had committed suicide had received a prescription for an antihypertensive drug within six months of their death. One hundred and forty controls—matched for age, sex, general practice, and index date—were selected from the same cohort. …