BACKGROUND: The minimum mortality temperature (MMT) or MMT percentile (MMTP) is an indicator of population susceptibility to nonoptimum temperatures. MMT and MMTP change over time; however, the changing directions show region-wide heterogeneity. We examined the heterogeneity of temporal changes in MMT and MMTP across multiple communities and in multiple countries. METHODS: Daily time-series data for mortality and ambient mean temperature for 699 communities in 34 countries spanning 1986-2015 were analyzed using a two-stage meta-analysis. First, a quasi-Poisson regression was employed to estimate MMT and MMTP for each community during the designated subperiods. Second, we pooled the community-specific temporally varying estimates using mixed-effects meta-regressions to examine temporal changes in MMT and MMTP in the entire study population, as well as by climate zone, geographical region, and country. RESULTS: Temporal increases in MMT and MMTP from 19.5 °C (17.9, 21.1) to 20.3 °C (18.5, 22.0) and from the 74.5 (68.3, 80.6) to 75.0 (71.0, 78.9) percentiles in the entire population were found, respectively. Temporal change was significantly heterogeneous across geographical regions (P < 0.001). Temporal increases in MMT were observed in East Asia (linear slope [LS] = 0.91, P = 0.02) and South-East Asia (LS = 0.62, P = 0.05), whereas a temporal decrease in MMT was observed in South Europe (LS = -0.46, P = 0.05). MMTP decreased temporally in North Europe (LS = -3.45, P = 0.02) and South Europe (LS = -2.86, P = 0.05). CONCLUSIONS: The temporal change in MMT or MMTP was largely heterogeneous. Population susceptibility in terms of optimum temperature may have changed under a warming climate, albeit with large region-dependent variations.

Air Health Science Division Health Canada Ottawa Canada

Center for Environmental and Respiratory Health Research Research Unit of Population Health Faculty of Medicine University of Oulu Oulu Finland

Center for Global Health School of Public Health Nanjing Medical University Nanjing China

Centro de Investigação em Saúde Pública Escola Nacional de Saúde Pública Universidade NOVA de Lisboa Lisbon Portugal

CIBER of Epidemiology and Public Health Madrid Spain

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

Climate Research Foundation Madrid Spain

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

Department of Earth Sciences University of Torino Torino Italy

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 Rollins School of Public Health Emory University Atlanta Georgia

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 Instituto Nacional de Saúde Dr Ricardo Jorge Porto Portugal

Department of Epidemiology Lazio Regional Health Service ASL Roma1 Rome Italy

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

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 Athens Greece

Department of Information and Statistics Chungnam National University Daejeon South Korea

Department of Mathematical Sciences Korea Advanced Institute of Science and Technology Daejeon South Korea

Department of Pathology University of Sao Paulo School of Medicine São Paulo Brazil

Department of Public Health and Clinical Medicine Umeå University Umeå Sweden

Department of Public Health Universidad de los Andes Santiago Chile

Department of Statistics and Computational Research Universitat de València València Spain

Department of Statistics Informatics Applications 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 UK

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

Environmental Research Group School of Public Health Imperial College London London UK

EPIUnit Instituto de Saude Publica Universidade do Porto Porto Portugal

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

Faculty of Geography Babes Bolay University Cluj Napoca Romania

Faculty of Health and Sport Sciences University of Tsukuba Tsukuba Japan

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

Graduate School of Public Health Seoul National University Seoul South Korea

IBE Chair of Epidemiology LMU Munich Munich Germany

Institute of Advanced Studies University of São Paulo São Paulo Brazil

Institute of Atmospheric Physics Czech Academy of Sciences Prague Czech Republic

Institute of Environment Health and Societies Brunel University London London United Kingdom

Institute of Environmental and Occupational Health Sciences National Taiwan University College of Public Health Taipei Taiwan

Institute of Environmental Assessment and Water Research Barcelona Spain

Institute of Epidemiology Helmholtz Zentrum München German Research Center for Environmental Health Neuherberg Germany

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

Institute of Social and Preventive Medicine University of Bern Bern Switzerland

Laboratory for Integrative and Translational Research in Population Health Porto Portugal

Laboratory of Management in Science and Public Health National Agency for Public Health of the Ministry of Health Chisinau Republic of Moldova

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

National Institute for Public Health and the Environment Centre for Sustainability and Environmental Health Bilthoven Netherlands

National Institute of Environmental Health Chinese Center for Disease Control and Prevention Beijing China

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 Health French National Public Health Agency Saint Maurice France

School of Biomedical Convergence Engineering Pusan National University Yangsan South Korea

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

School of Physics Technological University Dublin Dublin Ireland

School of Public Health and Institute of Environment and Human Health Anhui Medical University Hefei China

School of Public Health and Social Work Queensland University of Technology Brisbane Australia

School of Tropical Medicine and Global Health Nagasaki University Nagasaki Japan

Spanish Consortium for Research on Epidemiology and Public Health Madrid Spain

Swiss Tropical and Public Health Institute Allschwil Switzerland

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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