Advantages and limitation of research based on health registries

Introduction of the personal registration number (CPR number) in 1968 together with subsequent establishment of various registries containing administrative and  disease related data has opened unique research possibilities for Danish researchers. In an invited review article, Toft Sørensen et al discus advantages and limitations of research based on health registries. The authors conclude that registries provide an opportunity to conduct excellent epidemiological research but also have limitations.The study design and whether the data are suitable for answering the given research question must always be critically considered.