Comparison of Relationships Between the Number of Deaths Due to the 10 Leading Causes and Air Temperature in Hokkaido and Okinawa, Japan

Background Some literature reports an association between air temperature and mortality in certain diseases. However, the relationships between air temperature parameters and all causes of death have not been thoroughly explored in Japan. Objective This study examined the relationships between the number of deaths from the 10 leading causes and air temperature parameters in Hokkaido (the northernmost region) and Okinawa (the southernmost region) prefectures in Japan. Methods We collected monthly data on the number of deaths from the 10 leading causes and air temperature parameters in Hokkaido and Okinawa prefectures from January 2008 to December 2022 using information from official sources. Annual population data for each prefecture were also obtained. The relationships between the number of deaths and air temperature parameters were assessed through an ecological study. Results The mean air temperature was 9.59 ± 9.23 °C in Hokkaido and 23.46 ± 4.37 °C in Okinawa, with all temperature parameters significantly lower in Hokkaido than in Okinawa. The number of deaths from the 10 leading causes, excluding aspiration pneumonia, was significantly higher in Hokkaido for both sexes compared to Okinawa. In Hokkaido, deaths due to heart disease, cerebrovascular disease, pneumonia, accidents, and renal failure showed a significant correlation with all air temperature parameters for both sexes. In Okinawa, heart disease and cerebrovascular disease deaths were correlated with all air temperature parameters for both sexes. Conclusions The relationships between the number of deaths from the 10 leading causes and air temperature parameters differed between Hokkaido and Okinawa prefectures in Japan.