Population adaptation to heat waves and cold spells in East Asia

Background: Quantitative analysis of temperature variability greatly relies on the short-term effects of heat waves or cold spells. However, these time-series analyses are insufficient for the provision of evidence of human adaption to temperature variability. Aims: We examined mortality changes associated with the frequency of extreme conditions. Methods: We analyzed all-cause mortality associated with frequency of heat wave and cold spell in 15 Asian cities in three nations (Korea, Japan, and Taiwan). Heat waves and cold spells were determined in the top and bottom 5th percentile of temperature, respectively, and only those conditions which persisted for at least 2 days were included as extreme weather events. The corresponding mortality proportion and percentage of years with extreme weather events were analyzed using linear regression. Results: The relationship between extreme weather events and mortality differed by temperature range of the city location. Cities with less frequent heat waves showed a greater relative mortality from heat waves than cities with more frequent heat-waves. However, frequent cold spells showed similar risk for populations residing in areas of lower winter temperatures regardless of cold spell frequencies. Conclusion: This study found that populations respond differently to abnormal weather conditions depending on the temperature range (hot or cold).