We followed 828 nondemented residents of Hisayama Town, Kyushu, Japan, aged 65 years or older (88.3% of the elderly population) for 7 years starting in 1985 in order to determine the type-specific incidence of dementia and its risk factors in the general Japanese population. Only two subjects were lost to the follow-up, during which period 103 subjects developed dementia. Morphologic examination of the brains of 89 subjects (86.4%) was made by autopsy or CT. We made the initial diagnosis of dementia based on the DSM-III-R criteria, with the diagnoses of vascular dementia (VD) being based on the NINDS-AIREN criteria and Alzheimer's disease (AD) on the NINCDS-ADRDA criteria. The incidence of VD and AD increased with age for both sexes. 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 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 subjects whose brain morphology we 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 independent risk factors for the occurrence of VD. In contrast, age and a low score on Hasegawa's dementia scale were significant risk factors for AD, and physical activity was a significant preventive factor for AD.(ABSTRACT TRUNCATED AT 250 WORDS)

To elucidate the effect of glucose intolerance on cardiovascular disease in the current Japanese population, we performed a 75-g oral glucose tolerance test in 2,427 Hisayama residents aged 40-79 years in 1988, who were free from a previous history of stroke or myocardial infarction, and followed them prospectively for 5 years. The prevalence of diabetes (NIDDM) among men was 13% and that of impaired glucose tolerance (IGT) was 20%; the corresponding values for women were 9 and 19%, respectively. The age- and sex-adjusted incidence of cerebral infarction (6.5 per 1,000 person-years, P < 0.01) and coronary heart disease (5.0 per 1,000 person-years, P < 0.05) was significantly higher in subjects with NIDDM than in those with normal glucose tolerance (1.9 and 1.6 per 1,000 person-years, respectively). In addition, subjects with IGT and NIDDM had a higher risk of cardiovascular disease including stroke and coronary heart disease than did those with normal glucose tolerance after adjustment for age and sex, namely the relative risk for IGT was 1.9 (95% CI 1.2-3.2), and the relative risk for NIDDM was 3.0 (95% CI 1.8-5.2). These associations remained significant even after controlling for six other risk factors including hypertension in multivariate analysis. Our data suggest that NIDDM is a significant risk factor for both cerebral infarction and coronary heart disease and also that IGT itself is a risk factor for cardiovascular disease in the general Japanese population today.

We determined the population-based prevalence of diabetes mellitus in members of the Japanese community, Hisayama aged 40-79 years old by a 75-g oral glucose tolerance test. The basic population used to calculate diabetic prevalence was 1,077 men (72.8% of the whole population in the same age range) and 1,413 women (80.8%) including ten diabetic patients on insulin therapy. In addition, we compared the prevalence of history of diabetes which was acquired by interview or questionnaire, between participants and non-participants in the 75-g oral glucose tolerance test, but they were not statistically different. The age-adjusted prevalence of diabetes to world population was 12.7% for men and 8.4% for women, and that of impaired glucose tolerance was 19.6% for men and 18.4% for women. These figures were much higher than those previously reported from several Japanese communities. The results obtained from the present study could reveal true prevalence of diabetes among the Japanese population. In addition, the reasons for the increasing prevalence of diabetes among the recent Japanese population are also discussed.

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We compared type-specific prevalences of dementia between two surveys of Hisayama residents ≥ 65 years old conducted in 1985 and 1992. The overall age-adjusted prevalence was greatly decreased from 5.4% in 1985 to 3.3% in 1992 for men, while it was changed little from 7.5 to 6.3% for women. The prevalence of vascular dementia (VD) decreased during the intervening 7 years in men but not in women. The prevalence of Alzheimer’s type (SDAT) was the same in either sex. The ratio of VD to SDAT prevalence was 1.8 in 1985 but fell to 1.1 in 1992. The background factors responsible for this change are discussed.