INCIDENCE AND RISK-FACTORS OF VASCULAR DEMENTIA AND ALZHEIMERS-DISEASE IN A DEFINED ELDERLY JAPANESE POPULATION - THE HISAYAMA STUDY

We followed 828 nondemented residents of Hisayama Town, Kyushu,Japan, aged 65 years or older (88.3% of the elderly population) for 7 years s tarting in 1985 in order to determine the type-specific incidence of d ementia and its risk factors in the general Japanese population. Only two subjects were lost to the follow-up, during which period 103 subje cts developed dementia. Morphologic examination of the brains of 89 su bjects (86.4%) was made by autopsy or CT. We made the initial diagnosi s of dementia based on the DSM-III-R criteria, with the diagnoses of v ascular dementia (VD) being based on the NINDS-AIREN criteria and Alzh eimer's disease (AD) on the NINCDS-ADRDA criteria. The incidence of VD and AD increased with age for both sexes. The age-adjusted total inci dence (per 1,000 person-years) of dementia was 19.3 for men and 20.9 f or women. The corresponding rates for 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 subje cts whose brain morphology we examined, the most frequent type of stro ke was multiple lacunar infarcts (42%), but half these subjects lacked a stroke episode in their histories. Multivariate analysis showed tha t age, prior stroke episodes, systolic blood pressure, and alcohol con sumption were significant independent risk factors for the occurrence of VD. In contrast, age and a low score on Hasegawa's dementia scale w ere significant risk factors for AD, and physical activity was a signi ficant preventive factor for AD. Our findings suggest that asymptomati c stroke is an important factor in the development of VD, with age, pr ior stroke episodes, systolic blood pressure, and alcohol consumption being independent risk factors for its occurrence. Age and a low score on Hasegawa's dementia scale are significant risk factors for AD, wit h moderate physical activity having a statistically significant preven tive effect.