Background: Recent investigations have reported a decline in the heat-related mortality risk during the last decades. However, these studies are frequently based on modeling approaches that do not fully characterize the complex temperature–mortality relationship, and are limited to single cities or countries.
Objectives: We assessed the temporal variation in heat–mortality associations in a multi-country data set using flexible modelling techniques.
Methods: We collected data for 272 locations in Australia, Canada, Japan, South Korea, Spain, the United Kingdom, and the United States, with a total 20,203,690 deaths occurring in summer months between 1985 and 2012. The analysis was based on two-stage time-series models. The temporal variation in heat–mortality relationships was estimated in each location with time-varying distributed lag nonlinear models, expressed through an interaction between the transformed temperature variables and time. The estimates were pooled by country through multivariate meta-analysis.
Results: Mortality risk due to heat appeared to decrease over time in several countries, with relative risks associated to high temperatures significantly lower in 2006 compared with 1993 in the United States, Japan, and Spain, and a nonsignificant decrease in Canada. Temporal changes are difficult to assess in Australia and South Korea due to low statistical power, and we found little evidence of variation in the United Kingdom. In the United States, the risk seems to be completely abated in 2006 for summer temperatures below their 99th percentile, but some significant excess persists for higher temperatures in all the countries.
Conclusions: We estimated a statistically significant decrease in the relative risk for heat-related mortality in 2006 compared with 1993 in the majority of countries included in the analysis.
1Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom; 2Division of Epidemiology and Biostatistics, School of Population Health, University of Queensland, Brisbane, Queensland, Australia; 3Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan; 4Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, USA; 5National Center for Disaster Preparedness, Earth Institute, Columbia University, New York, New York, USA; 6Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ontario, Canada; 7Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; 8Institute of Environmental Assessment and Water Research (IDAEA), Spanish Council for Scientific Research (CSIC), Barcelona, Spain; 9Department of Epidemiology, Lazio Regional Health Service, Rome, Italy; 10School of Public Health and Social Work, Queensland University of Technology, Brisbane, Queensland, Australia; 11Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; 12Graduate School of Public Health, Seoul National University, Seoul, Republic of Korea; 13Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
Recommended Citation:
Antonio Gasparrini,1 Yuming Guo,2 Masahiro Hashizume,et al. Temporal Variation in Heat–Mortality Associations: A Multicountry Study[J]. Environmental Health Perspectives,2015-01-01,Volume 123(Issue 11):1200