Regional variance of cerebrovascular mortality in Japan.

Cerebrovascular disease is a chronic disease reflecting the influence of many different factors. In postwar Japan, the disease has been the primary cause of death and its mortality has shown the obvious regional variance. The purpose of this study is to present and appreciate the regional variance of the disease in Japan. The first step was the observation of the general regional variance of the disease by the trend surface analysis. Next came the classification of the regional types of the disease, which may be the regional character, in order to appreciate the detail of the variance of the disease. Lastly, the factor of the regional variance was examined by temperature in winter. The general pattern of distribution reveals cerebrovascular mortality to be higher in the east of the country and lower in the west. In more general terms the highest mortality is located in northeast Japan, except Hokkaido, and the lowest in southwest Japan, especially in the Inland Sea region. The fact that the higher mortality is in the mountainous region and the lower is in the plains and basins suggests dependence on geographical variations between both regions. There is a strong relationship in Japan between cerebrovascular mortality and the lower temperatures of winter. The exception is Hokkaido, where the lower mortality may be the result of other regional factors such as unconventional lifestyle.