Statistical Methods in Medical Research 2009; 18: 81–105 Efficient sampling approaches to address confounding in database studies

Administrative and other population-based databases are widely used in pharmacoepidemiology to study the unintended effects ofmedications. They allow investigators to study large case series, and they document prescriptionmedication exposure without having to contact individuals ormedical charts, or rely on human recall. However, such databases often lack information on potentially important confounding variables. This review describes some of the sampling approaches and accompanying data-analysis methods that can be used to assess, and deal efficiently with, such confounding.