Multisite time-series studies for temperature-related mortality have been conducted mainly in the United States and Europe, but are lacking in Asia. This multisite time-series study examined mortality related to extreme temperatures (both cold and hot) in Northeast Asia, focusing on 15 cities of 3 high-income countries.
This study includes 3 cities in Taiwan for 1994–2007, 6 cities in Korea for 1992–2010, and 6 cities in Japan for 1972–2009. We used 2-stage Bayesian hierarchical Poisson semiparametric regression to model the nonlinear relationship between temperature and mortality, providing city-specific and country-wide estimates for cold and heat effects. Various exposure time frames, age groups, and causes of death were considered.
Cold effects had longer time lags (5–11 days) than heat effects, which were immediate (1–3 days). Cold effects were larger for cities in Taiwan, whereas heat effects were larger for cities in Korea and Japan. Patterns of increasing effects with age were observed in both cold and heat effects. Both cold and heat effects were larger for cardiorespiratory mortality than for other causes of death. Several city characteristics related to weather or air pollution were associated with both cold and heat effects.
Mortality increased with either cold or hot temperature in urban populations of high-income countries in Northeast Asia, with spatial variations of effects among cities and countries. Findings suggest that climate factors are major contributors to the spatial heterogeneity of effects in this region, although further research is merited to identify other factors as determinants of variability.
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From the aDepartment of Mathematical Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea; bInstitute of Environmental Medicine, Seoul National University Medical Research Center & Environmental Health Center, Seoul National University College of Medicine, Seoul, South Korea; cFaculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan; dEnvironmental and Occupational Medicine, National Taiwan University, Taipei, Taiwan; eDepartment of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; fSchool of Forestry and Environmental Studies, Yale University, New Haven, CT.; and gDepartment of Biostatistics and Epidemiology, Graduate School of Public Health & Institute of Health and Environment, Seoul National University, Seoul, South Korea.
Submitted 8 March 2014; accepted 30 September 2014.
Supported by the International Research & Development Program (2012K1A3A1A12054839), the Global Research Laboratory Program (K21004000001-10A0500-00710), the Young Investigator Research Fund (20110013111), and the Women Scientist Research Program (2012R1A1A3005549) of the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology of Korea.
The authors report no conflicts of interest.
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Correspondence: Ho Kim, Department of Biostatistics and Epidemiology, Graduate School of Public Health & Institute of Health and Environment, Seoul National University, 1 Kwanak-ro, Kwanak-gu, Seoul 151–742, Korea. E-mail: email@example.com.