Global warming is increasingly recognized as a threat to the survival of human beings, because it could cause a serious increase in the occurrence of diseases due to environmental heat during intermittent hot weather. To assess the direct impact of extremely hot weather on human health, we investigated heat-related deaths in Japan from 1968 through 1994, analyzing the data to determine the distribution of the deaths by age and their correlation to the incidence of hot days in summer. Vital Statistics of Japan, published by the Ministry of Health and Welfare of Japan, was the source of the heat-related mortality data employed in this study. Meteorological data were obtained from the District Meteorological Observatories in Tokyo and Osaka, the two largest cities in Japan. Heat-related deaths were most prone to occur on days with a peak daily temperature above 38°C, and the incidence of these deaths showed an exponential dependence on the number of hot days. Thus, even a small rise in atmospheric temperature may lead to a considerable increase in heat-related mortality, indicating the importance of combating global warming. Furthermore, half (50.1%) of the above-noted deaths occurred in children (4 years and under) and the elderly (70 years and over) irrespective of gender, indicating the vulnerability of these specific age groups to heat. Since a warmer climate is predicted in the future, the incidence of heat waves will increase, and more comprehensive measures, both medical and social, should be adopted for children of 4 years and younger the elderly to prevent heat-related deaths in these age groups.

https://link.springer.com/article/10.1007/s004840050127