Spatial and Temporal Features of Heat Stroke Mortality in Japan and Their Relation to Temperature Variations, 1999–2014

Abstract

Regional and seasonal features and the interannual variations of heat stroke mortality in Japan are examined using the Vital Statistics of Japan from 1999 to 2014. We found that heat stroke mortality has different spatial patterns and different dependence on temperature, according to age groups. For the age group under 60, mortality is positively correlated with seasonal mean temperature and is higher in the southern regions of Japan, while the mortality of the age group 80 and over is positively correlated with summer peak temperature, being high in some prefectures in northern to central Honshu, the main island of Japan. The latter group also shows larger interannual variations and a higher increasing trend than the former. As for seasonal variation, heat stroke mortality is high in July–August, with a peak period delay northward, which corresponds to a later temperature peak. Moreover, mortality tends to be higher in July than August by 40–50% even if the monthly mean temperature is equal. These findings are expected to provide a statistical basis to cope with heat load disasters in Japan.