The study of this research theme has often been restricted by the limited size of the cohort of staff, not allowing the study of sometimes rare drug exposures, and poverty of the information collected on drug exposures. Thus, most studies focuses on families of molecules among the most prescribed. In addition, we now know that the pathophysiological process underlying Alzheimer's disease (representing 2/3 of dementia), actually begins more than 10 years before the diagnosis of dementia. It is therefore essential to have a setback of several years between drug exposure and diagnosis of dementia to assess their role in the genesis and evolution of the disease.