Epidemiology of dementia.

Descriptive epidemiologic studies demonstrate that the risk of dementia in general and of Alzheimer's disease in particular increases with advancing age, and the risk appears to be slightly greater among women. There is no firm epidemiologic evidence to suggest that Alzheimer's disease represents two distinct conditions. Demographic projections indicate that the number of affected individuals is expected to grow as the elderly segment of our population increases. Analytic epidemiologic studies have yielded a number of positive findings, including an excess of dementia, Down's syndrome, and lymphoma in the relatives of index cases of Alzheimer's disease and a greater than expected frequency of head trauma and thyroid disease among those with Alzheimer's disease. Results have not been consistent from study to study and await further confirmation. It is hoped that findings of future analytic investigations will provide much needed information required for the development of rational programs of treatment and prevention of this major health problem.