BACKGROUND: Heterogeneity in temperature-mortality relationships across locations may partly result from differences in the demographic structure of populations and their cause-specific vulnerabilities. Here we conduct the largest epidemiological study to date on the association between ambient temperature and mortality by age and cause using data from 532 cities in 33 countries. METHODS: We collected daily temperature and mortality data from each country. Mortality data was provided as daily death counts within age groups from all, cardiovascular, respiratory, or noncardiorespiratory causes. We first fit quasi-Poisson regression models to estimate location-specific associations for each age-by-cause group. For each cause, we then pooled location-specific results in a dose-response multivariate meta-regression model that enabled us to estimate overall temperature-mortality curves at any age. The age analysis was limited to adults. RESULTS: We observed high temperature effects on mortality from both cardiovascular and respiratory causes compared to noncardiorespiratory causes, with the highest cold-related risks from cardiovascular causes and the highest heat-related risks from respiratory causes. Risks generally increased with age, a pattern most consistent for cold and for nonrespiratory causes. For every cause group, risks at both temperature extremes were strongest at the oldest age (age 85 years). Excess mortality fractions were highest for cold at the oldest ages. CONCLUSIONS: There is a differential pattern of risk associated with heat and cold by cause and age; cardiorespiratory causes show stronger effects than noncardiorespiratory causes, and older adults have higher risks than younger adults.

Center for Climate Change Adaptation National Institute for Environmental Studies Tsukuba Japan

Center for Environmental and Respiratory Health Research University of Oulu Oulu Finland

CIBER de Epidemiología y Salud Pública Madrid Spain

Climate Air Quality Research Unit School of Public Health and Preventative Medicine Monash University Melbourne Australia

Climate Research Foundation Madrid Spain

Climatology Research Group Institute of Landscape Ecology University of Münster Münster Germany

College of Health Medicine and Life Sciences Brunel University London London UK

Department of Earth Sciences University of Torino Turin Italy

Department of Environmental Health Faculty of Public Health University of Medicine and Pharmacy at Ho Chi Minh City Ho Chi Minh City Vietnam

Department of Environmental Health Harvard T H Chan School of Public Health Harvard University Boston Massachusetts

Department of Environmental Health Instituto Nacional de Saúde Dr Ricardo Jorge Porto Portugal

Department of Environmental Health National Institute of Public Health Cuernavaca Morelos Mexico

Department of Environmental Health School of Public Health Fudan University Shanghai China

Department of Environmental Health University of São Paulo São Paulo Brazil

Department of Epidemiology and Preventive Medicine School of Public Health and Preventive Medicine Monash University Melbourne Australia

Department of Epidemiology Lazio Regional Health Service Rome Italy

Department of Global Health Policy Graduate School of Medicine The University of Tokyo Tokyo Japan

Department of Hygiene Epidemiology and Medical Statistics National and Kapodistrian University of Athens Greece

Department of Pathology Faculty of Medicine University of São Paulo São Paulo Brazil

Department of Public Health and Clinical Medicine Umeå University Umeå Sweden

Department of Statistics and Computational Research Universitat de València València Spain

Department of Statistics Computer Science and Applications G Parenti University of Florence Florence Italy

Environment and Health Modelling Lab Department of Public Health Environments and Society London School of Hygiene and Tropical Medicine London United Kingdom

Environmental and Occupational Medicine National Taiwan University College of Medicine and NTU Hospital Taipei Taiwan

Environmental Health Science and Research Bureau Health Canada Ottawa Canada

EPIUnit Instituto de Saúde Pública Universidade do Porto Porto Portugal

Faculty of Environmental Sciences Czech University of Life Sciences Prague Czech Republic

Faculty of Geography and Environmental Sciences Hakim Sabzevari University Sabzevar Khorasan Razavi Iran

Gangarosa Department of Environmental Health Rollins School of Public Health Emory University Atlanta

Graduate School of Public Health Seoul National University Seoul South Korea

INSPER São Paulo Brazil

Institute for Global Health University College London London UK

Institute of Atmospheric Physics Czech Academy of Sciences Prague Czech Republic

Institute of Environmental Assessment and Water Research Spanish Council for Scientific Research Barcelona Spain

Institute of Family Medicine and Public Health University of Tartu Tartu Estonia

Institute of Social and Preventive Medicine University of Bern Bern Switzerland

Laboratório para a Investigação Integrativa e Translacional em Saúde Populacional Porto Portugal

Medical Research Center Oulu Oulu University Hospital and University of Oulu Oulu Finland

National Institute of Environmental Health Science National Health Research Institutes Zhunan Taiwan

Norwegian Institute of Public Health Oslo Norway

Oeschger Center for Climate Change Research University of Bern Bern Switzerland

Santé Publique France Department of Environmental and Occupational Health French National Public Health Agency Saint Maurice France

School of Biomedical Convergence Engineering College of Information and Biomedical Engineering Pusan National University Yangsan South Korea

School of Epidemiology and Public Health Faculty of Medicine University of Ottawa Ottawa Canada

School of Population Health and Environmental Sciences King's College London UK

School of Tropical Medicine and Global Health Nagasaki University Nagasaki Japan

Swiss Tropical and Public Health Institute Allschwil Switzerland

Technological University Dublin Ireland

Universidad de Buenos Aires Facultad de Ciencias Sociales Instituto de Investigaciones Gino Germani Buenos Aires Argentina

University of Basel Basel Switzerland

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