Geographical distributions of cerebrocardiovascular diseases in Japan: 1969–1974

Abstract

The mortality rate for cerebrovascular disease has been the leading cause of death in Japan since 1951 followed by malignant neoplasm and cardiovascular disease. Both cerebro- and cardiovascular diseases are currently responsible for about 40% of all causes of death in Japan, emerging as the most important disease problem.

The purpose of this study is to examine the geographic variations in standardized mortality ratio (SMR) for these diseases on a county-by-county basis across Japan during 1969–1974 and to investigate environmental factors which might be associated with these diseases.

Environmental data such as the food expenditures, latitude and longitude in each county were obtained from the reliable sources. In order to study the association between these environmental factors and the disease, the counties were divided into two groups: one group consists of counties with the SMR more than 120 and significant at 5% level (high SMR group) and the other, those with the SMR less than 80 and significant at 5% level (low SMR group). The environmental conditions were then compared between these two groups.

Cerebral haemorrhage and cerebral infarction accounted for approximately 80% of all cerebrovascular diseases deaths in Japan in 1978. The SMR for cerebral haemorrhage and cerebral infarction in males is high in the northeast and low in the southwest but the most striking clustering of elevated SMR occurs in the Tohoku Region. The patterns for females for these diseases are similar. The geographic patterns for ischaemic heart disease are less pronounced than those for cerebral infarction and haemorrhage, while the maps of hypertensive heart disease show higher SMR in the southern part of the country and Kanto areas.

Excess intake of salt and insufficient intake of animal proteins which were observed in the high SMR group seem to play an important role as risk factors of cerebrocardiovascular diseases in Japan.