[Epidemiology of dementia: the Hisayama study].

A prospective cohort study has been conducted in the elderly of the town of Hisayama in Japan since 1985 to elucidate the trends in the prevalence of dementia and examine risk and protective factors for dementia in the general Japanese population. We revealed that the prevalence of all-cause dementia and Alzheimer's disease significantly increased from 1985 to 2005. In our prospective study, diabetes was associated with significantly increased risk of Alzheimer's disease and vascular dementia, while midlife and late-life hypertensions were significant risk factors for vascular dementia but not for Alzheimer's disease. Meanwhile, physical activity and a dietary pattern which was roughly correspondent to a customary Japanese diet were associated with lower risk of dementia in our population.