[Prevalence, incidence, and risk factors of vascular dementia: the Hisayama study]

We studied the type-specific prevalence, incidence, and risk factors of vascular dementia in elderly persons from a Japanese community of Hisayama. In 1985, we performed a screening survey of dementia among 887 Hisayama residents > or = 65 years or older (screening rate, 95%), using clinical information and Hasegawa's dementia scale, and consequently, determined 59 subjects as demented. Of these, 58 cases underwent brain examinations at autopsy and/or computed tomography during the subsequent 12.5 years. Among the 58 cases of dementia, the frequency of vascular dementia (VD) was 43%: the rate was 2 times higher than that for Alzheimer's disease (AD). In the subjects of VD, the most frequent type of stroke was due to small-artery disease, which caused multiple lacunar infarction (40%) and Binswanger's disease (12%). We also followed the 826 nondemented subjects for 7 years starting in 1985 in order to determine the type-specific incidence of dementia and its risk factors in the general population. The age-adjusted total incidence (per 1,000 person-years) of dementia was 19.3 for men and 20.9 for women. The corresponding rates of VD were 12.2 for men and 9.0 for women, and for AD 5.1 for men and 10.9 for women. Among the VD subjects whose brain morphology was examined, the most frequent type of stroke was multiple lacunar infarcts (42%), but half these subjects lacked a stroke episode in their histories. Multivariate analysis showed that age, prior stroke episodes, systolic blood pressure, and alcohol consumption were significant risk factors for the occurrence of VD.