title: Mortality risk attributable to high and low ambient temperature: a multicountry observational study.
abstract: BACKGROUND
  Although studies have provided estimates of premature deaths attributable to either heat or cold in selected countries, none has so far offered a systematic assessment across the whole temperature range in populations exposed to different climates. We aimed to quantify the total mortality burden attributable to non-optimum ambient temperature, and the relative contributions from heat and cold and from moderate and extreme temperatures.
  
  
  METHODS
  We collected data for 384 locations in Australia, Brazil, Canada, China, Italy, Japan, South Korea, Spain, Sweden, Taiwan, Thailand, UK, and USA. We fitted a standard time-series Poisson model for each location, controlling for trends and day of the week. We estimated temperature-mortality associations with a distributed lag non-linear model with 21 days of lag, and then pooled them in a multivariate metaregression that included country indicators and temperature average and range. We calculated attributable deaths for heat and cold, defined as temperatures above and below the optimum temperature, which corresponded to the point of minimum mortality, and for moderate and extreme temperatures, defined using cutoffs at the 2·5th and 97·5th temperature percentiles.
  
  
  RESULTS
  We analysed 74,225,200 deaths in various periods between 1985 and 2012. In total, 7·71% (95% empirical CI 7·43-7·91) of mortality was attributable to non-optimum temperature in the selected countries within the study period, with substantial differences between countries, ranging from 3·37% (3·06 to 3·63) in Thailand to 11·00% (9·29 to 12·47) in China. The temperature percentile of minimum mortality varied from roughly the 60th percentile in tropical areas to about the 80-90th percentile in temperate regions. More temperature-attributable deaths were caused by cold (7·29%, 7·02-7·49) than by heat (0·42%, 0·39-0·44). Extreme cold and hot temperatures were responsible for 0·86% (0·84-0·87) of total mortality.
  
  
  CONCLUSIONS
  Most of the temperature-related mortality burden was attributable to the contribution of cold. The effect of days of extreme temperature was substantially less than that attributable to milder but non-optimum weather. This evidence has important implications for the planning of public-health interventions to minimise the health consequences of adverse temperatures, and for predictions of future effect in climate-change scenarios.
  
  
  BACKGROUND
  UK Medical Research Council.
authors.affiliation: Department of Medical Statistics, London School of Hygiene & Tropical Medicine, London, UK. Electronic address: antonio.gasparrini@lshtm.ac.uk.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gasparrini
authors.affiliation: Department of Epidemiology and Biostatistics, School of Population Health, University of Queensland, Brisbane, QLD, Australia.
authors.forename: Yuming
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hashizume
authors.affiliation: Interdisciplinary School of Health Sciences, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Lavigne
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.affiliation: Institute of Environmental Assessment and Water Research (IDAEA), Spanish Council for Scientific Research (CSIC), Barcelona, Spain.
authors.forename: Aurelio
authors.initials: A
authors.lastname: Tobias
authors.affiliation: School of Public Health and Social Work, Queensland University of Technology, Brisbane, QLD, Australia.
authors.forename: Shilu
authors.initials: S
authors.lastname: Tong
authors.affiliation: Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Joacim
authors.initials: J
authors.lastname: Rocklöv
authors.affiliation: Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Bertil
authors.initials: B
authors.lastname: Forsberg
authors.affiliation: Department of Epidemiology, Lazio Regional Health Service, Rome, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Leone
authors.affiliation: Department of Epidemiology, Lazio Regional Health Service, Rome, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: De Sario
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
authors.affiliation: Department of Environmental and Occupational Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yue-Liang Leon
authors.initials: YL
authors.lastname: Guo
authors.affiliation: Department of Public Health, National Taiwan University, Taipei, Taiwan.
authors.forename: Chang-fu
authors.initials: CF
authors.lastname: Wu
authors.affiliation: Department of Environmental Health, Fudan University, Shanghai, China.
authors.forename: Haidong
authors.initials: H
authors.lastname: Kan
authors.affiliation: Graduate School of Public Health & Institute of Health and Environment, Seoul National University, Seoul, Republic of Korea.
authors.forename: Seung-Muk
authors.initials: SM
authors.lastname: Yi
authors.affiliation: Department of Pathology, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Micheline
authors.initials: M
authors.lastname: de Sousa Zanotti Stagliorio Coelho
authors.affiliation: Department of Pathology, School of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: Paulo Hilario Nascimento
authors.initials: PH
authors.lastname: Saldiva
authors.affiliation: Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Honda
authors.affiliation: Graduate School of Public Health & Institute of Health and Environment, Seoul National University, Seoul, Republic of Korea.
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Armstrong
mesh_terms: D002980:Climate; D003080:Cold Temperature / Q000009:adverse effects*; D014943:Global Health / Q000706:statistics & numerical data*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D009026:Mortality; D018570:Risk Assessment / Q000379:methods