Clinical and epidemiological aspects of dementia in the elderly.

Dementia of the Alzheimer's type (DAT) is the most significant disease of the aging brain. Descriptive epidemiology of DAT found a constant doubling of prevalence rates every 5 years. Analytic epidemiology so far failed to reliably detect risk factors for DAT other than age. This might depend on the difficulties encountered in the clinical diagnosis and differential diagnosis of dementia in the elderly, which are discussed with special reference to 1) the definition of dementia, to 2) the grading of severity of dementia, to 3) the differentiation between dementia and depression, and to 4) the differentiation between multi-infarct dementia and DAT.