Ambient Temperature and Mortality: An International Study in Four Capital Cities of East Asia

Abstract

ISEE-0258 Background and Objective: Extreme ambient temperature has been associated with increased daily mortality across the world. We describe the ambient temperature-mortality association for four capital cities in East Asia, Seoul, Beijing, Tokyo, and Taipei, and identify a threshold temperature for each city and the percent increase in mortality. Methods: We observed that threshold temperatures vary by latitude. We adapted generalized linear modeling with natural cubic splines (GLM+NS) to examine the association between daily mean apparent temperature and total mortality, as well as mortality due to respiratory and cardiovascular causes in a threshold model. We conducted a time-series analysis adjusting for day of the week and long-term time trend. The study period differed by city. Results: The threshold temperature for all seasons was estimated to be 30.1–33.5°C, 31.3–32.3°C, 29.4–30.8°C, and 25.2–31.5°C for Seoul, Beijing, Tokyo, and Taipei, respectively, on the same day. For the summer season, the threshold temperature was 33.2–34.2°C, 30.8–29.7°C, 31.5°C, and 30.7–31.5°C for Seoul, Beijing, Tokyo, and Taipei, respectively. For the mean daily apparent temperature increase of 1°C above the thresholds in Seoul, Tokyo, and Taipei, estimated percentage increases in daily total mortality were 2.7 (95% confidence interval (CI) = 2.2–3.1), 1.7 (95% CI = 1.5–2.0), and 4.3 (95% CI = 2.9–5.7), respectively. Beijing provided no total mortality counts. Estimated percentage increases were 2.7–10.5 for respiratory mortality, 1.1–9.3 for cardiovascular mortality in 4 cities. Conclusions: This study identified increased mortality due to exposure to elevated apparent temperature. The importance of effects of apparent temperature and city-specific threshold temperatures suggests that analyses of the impact of climate change should take regional differences into consideration.