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Environ Int. 2018 Feb;111:239-246. doi: 10.1016/j.envint.2017.11.006. Epub 2017 Dec 20.

A multi-country analysis on potential adaptive mechanisms to cold and heat in a changing climate.

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Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom. Electronic address:
Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
Department of Mathematical Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea.
Department of Clinical Epidemiology and Biostatistics, Children's Medical Center, Shanghai Jiao-Tong University, Shanghai, China; School of Public Health and Institute of Environment and Population Health, Anhui Medical University, Hefei, China; School of Public Health and Social Work, Queensland University of Technology, Brisbane, Australia.
Institute of Environmental Assessment and Water Research (IDAEA), Spanish Council for Scientific Research (CSIC), Barcelona, Spain.
Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Canada.
Institute of Advanced Studies, University of São Paulo, São Paulo, Brazil.
School of Physics, Dublin Institute of Technology, Dublin, Ireland.
Institute for Environment, Health and Societies, Brunel University London, London, United Kingdom.
Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.
Graduate School of Public Health, Seoul National University, Seoul, Republic of Korea.
Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA.



Temporal variation of temperature-health associations depends on the combination of two pathways: pure adaptation to increasingly warmer temperatures due to climate change, and other attenuation mechanisms due to non-climate factors such as infrastructural changes and improved health care. Disentangling these pathways is critical for assessing climate change impacts and for planning public health and climate policies. We present evidence on this topic by assessing temporal trends in cold- and heat-attributable mortality risks in a multi-country investigation.


Trends in country-specific attributable mortality fractions (AFs) for cold and heat (defined as below/above minimum mortality temperature, respectively) in 305 locations within 10 countries (1985-2012) were estimated using a two-stage time-series design with time-varying distributed lag non-linear models. To separate the contribution of pure adaptation to increasing temperatures and active changes in susceptibility (non-climate driven mechanisms) to heat and cold, we compared observed yearly-AFs with those predicted in two counterfactual scenarios: trends driven by either (1) changes in exposure-response function (assuming a constant temperature distribution), (2) or changes in temperature distribution (assuming constant exposure-response relationships). This comparison provides insights about the potential mechanisms and pace of adaptation in each population.


Heat-related AFs decreased in all countries (ranging from 0.45-1.66% to 0.15-0.93%, in the first and last 5-year periods, respectively) except in Australia, Ireland and UK. Different patterns were found for cold (where AFs ranged from 5.57-15.43% to 2.16-8.91%), showing either decreasing (Brazil, Japan, Spain, Australia and Ireland), increasing (USA), or stable trends (Canada, South Korea and UK). Heat-AF trends were mostly driven by changes in exposure-response associations due to modified susceptibility to temperature, whereas no clear patterns were observed for cold.


Our findings suggest a decrease in heat-mortality impacts over the past decades, well beyond those expected from a pure adaptation to changes in temperature due to the observed warming. This indicates that there is scope for the development of public health strategies to mitigate heat-related climate change impacts. In contrast, no clear conclusions were found for cold. Further investigations should focus on identification of factors defining these changes in susceptibility.


Adaptation; Climate change; Cold; Heat; Mortality

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