[Relationship between daily high temperature and mortality in Kyushu, Japan]

Abstract

We analyzed the relationship between daily high temperature and mortality in Kyushu, Japan, 1972-1990. Mortality rate was obtained by dividing the number of deaths in a certain daily high temperature category by person-days in the same category. The results were as follows: (1) With daily high temperature on the x-axis and mortality rate on the y-axis, the relationship between the two variables appeared to be V-shaped. The minimum mortality rate was observed at the 28 degrees C-33 degrees C level. (2) Among all deaths at 33+ degrees C level, the proportion of deaths from "excessive heat" never exceeded 0.4%. This suggested that heat stroke is not a major contributor to the V-shape formation. (3) The V-shape was observed even in 1990, suggesting that the rapid spread of air conditioners did not alter the relationship between daily high temperature and mortality rate. (4) For the 0-4 years age group, mortality was not temperature dependent. However, the 5-14 years age group showed high mortality rates at 33+ degrees C. This may be attributed to outdoor activities during summer. After 30 years of age, the overall mortality rates rose with age, with greater increases at lower ambient temperature levels. As a result, the 65+ years age group had the greatest temperature dependence. (5) Deaths from respiratory diseases, circulatory diseases, and senility were highly temperature dependent, whereas death from cancer was not temperature dependent. Deaths from digestive diseases, infectious diseases, and accidents showed moderate temperature dependence.