Epidemiology of Alzheimer's disease.

Epidemiologic studies of disease fall into two large categories: descriptive and analytic. Both approaches have been used in studies of dementia and Alzheimer's disease (AD). The prevalence of dementia in persons age 65 and older in North America is approximately 6 to 10%, with AD accounting for two-thirds of these cases. If milder cases are included, the prevalence rates double. Only age and family history of dementia are consistently associated with AD in all studies, but putative protective agents such as estrogen, NSAIDs, and vitamin E are undergoing clinical trials.