Abstract
Cerebrovascular disease is a chronic disease which relates not only to some specific pathological factors but also to many regional elements. After World War II, cerebrovascular disease has been the primary cause of death in Japan (Fig. 1) and its mortality (C. D. M.) has shown obvious regional variance. The purpose of this study is to present and grasp the regional variance of C. D. M, in Japan.
The first step of the analysis was the observation of regional variance of C. D. M. in Japan. Standardized motry ality ratio (SMR) was adopted in this study as the index of C. D. M., which was calculated with the number of deaths for cities, towns and villages (1968-1974). Then the polynominal trend surface analysis was applied to analyze the general regional pattern.
The second step was to classify the C. D. M. regions, which were defined by the combination of regional elements related to C. D. M., into several types in order to easily grasp the regionality of C. D. M. regions. To this end the residual from the 6 th order trend surface was analyzed.
Lastly, in order to explain the regional patterns of C. D. M. in Japan, the relationship between C. D. M. and temperature in winter which seemed to be one of the main factors of C. D. M. was considered.
Main results obtained are as follows:
1. The general regional pattern of C. D. M. in Japan is higher to east and lower to west. The 6 th order trend surface of C. D. M, shows the regional pattern which is the highest in the Tohoku district and the lowest in the Inland Sea district. But the C. D. M. of Hokkaido is the lower district in eastern Japan and that of Kyushu is the higher district in western Japan (Fig. 2).
2. The analysis of the residual from the 6 th order trend surface shows six types of C. D. M. regions (Figs. 3 and 4, Table 2):
A type: positive residual in high death region
B type: negative residual in high death region
C type: positive residual in low death region
D type: negative residual in low death region
E type: no residual in high and low death region
F type: medium death region
In general, A and C types, characterized by higher death rates, are located in mountainous regions, while B and D types with lower death rates are found in plains.
3. As the result of regression analysis, about 50 per cent of the regional variance of C. D. M. are explained by temperature in winter (Fig. 5). It means that C. D. M. is affected by the man's exposure to lower temperature. Hokkaido, however, deviated from this relation-ship. It is probably because its living conditions, including the degree of room heating, eating habits, etc., are much different from those in other regions in Japan.
