French health insurance databases: What interest for medical research?

French health insurance databases are organized since 2003 into a huge digital data warehouse, the Système national d'information inter-régime de l'assurance maladie (SNIIR-AM). It covers the entire French population (65 million inhabitants). In order to facilitate studies on more frequent conditions, a random sample of 1/97th of national health system beneficiaries has been built since 2005, called the échantillon généraliste des bénéficiaires (EGB). The aim of this article is to describe the main characteristics of the SNIIR-AM and the EGB, to detail their accessibility according to French law, and to present their strengths and limits. It is illustrated with the most recent studies conducted in these databases. These databases include demographic, out-hospital reimbursement (including drug dispensing), medical (costly long-term diseases, occupational diseases, sick-leaves…), and in-hospital data. All these data are prospectively recorded, individualized, made anonymous and linkable. Consequently, the SNIIR-AM is a very useful data source for epidemiological, pharmacoepidemiological and health economics studies, particularly for rare diseases. The EGB is appropriate for long-term research on more frequent diseases.