[Epidemiology of Alzheimer's type dementia]

Although still fragmentary, currently available epidemiologic data allow an analysis of the magnitude of the problem raised by Alzheimer type dementia. Its prevalence after 65 years of age varies between 1 and 5.8 p. 100, increasing markedly with advancing age to reach, from about 0.1 p. 100 between 55 and 65 years, 1 p. 100 between 65 and 74 and 10 p. 100 beyond 85 years. Based on these data it can be estimated that there are presently about 300,000 patients 60 years of age or over with Alzheimer type dementia (ATD) in France. The only risk factor for ATD identified at the present time is age but a family history of dementia could constitute a further risk factor for the disease. Progress in the field of epidemiology of ATD requires the development and validation of diagnostic criteria and standardized measuring instruments, allowing comparison of results of studies conducted by different teams in different countries, nearly impossible up to the present.