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Association between ambient temperature and mortality risk and burden: time series study in 272 main Chinese cities

BMJ 2018; 363 doi: https://doi.org/10.1136/bmj.k4306 (Published 31 October 2018) Cite this as: BMJ 2018;363:k4306
  1. Renjie Chen, associate professor1 2,
  2. Peng Yin, associate professor3,
  3. Lijun Wang, associate professor3,
  4. Cong Liu, PhD student1,
  5. Yue Niu, PhD student1,
  6. Weidong Wang, graduate student1,
  7. Yixuan Jiang, graduate student1,
  8. Yunning Liu, research assistant3,
  9. Jiangmei Liu, research assistant3,
  10. Jinlei Qi, research assistant3,
  11. Jinling You, research assistant3,
  12. Haidong Kan, professor1 2 4,
  13. Maigeng Zhou, professor3
  1. 1School of Public Health, Key Lab of Public Health Safety of the Ministry of Education and NHC Key Laboratory of Health Technology Assessment, Fudan University, Shanghai, China
  2. 2Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Fudan University, Shanghai, China
  3. 3National Center for Chronic and Noncommunicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 27 Nanwei Road, Xicheng District, Beijing 100050, China
  4. 4Key Laboratory of Reproduction Regulation of National Population and Family Planning Commission, Shanghai Institute of Planned Research, Institute of Reproduction and Development, Fudan University, Shanghai, China
  1. Correspondence to: M Zhou maigengzhou{at}126.com
  • Accepted 20 September 2018

Abstract

Objectives To examine the association between temperature and cause specific mortality, and to quantify the corresponding disease burden attributable to non-optimum ambient temperatures.

Design Time series analysis.

Setting 272 main cities in China.

Population Non-accidental deaths in 272 cities covered by the Disease Surveillance Point System of China, from January 2013 to December 2015.

Main outcomes and measures Daily numbers of deaths from all non-accidental causes and main cardiorespiratory diseases. Potential effect modifiers included demographic, climatic, geographical, and socioeconomic characteristics. The analysis used distributed lag non-linear models to estimate city specific associations, and multivariate meta-regression analysis to obtain the effect estimates at national and regional levels.

Results 1 826 186 non-accidental deaths from total causes were recorded in the study period. Temperature and mortality consistently showed inversely J shaped associations. At the national average level, relative to the minimum mortality temperature (22.8°C, 79.1st centile), the mortality risk of extreme cold temperature (at −1.4°C, the 2.5th centile) lasted for more than 14 days, whereas the risk of extreme hot temperature (at 29.0°C, the 97.5th centile) appeared immediately and lasted for two to three days. 14.33% of non-accidental total mortality was attributable to non-optimum temperatures, of which moderate cold (ranging from −1.4 to 22.8°C), moderate heat (22.8 to 29.0°C), extreme cold (−6.4 to −1.4°C), and extreme heat (29.0 to 31.6°C) temperatures corresponded to attributable fractions of 10.49%, 2.08%, 1.14%, and 0.63%, respectively. The attributable fractions were 17.48% for overall cardiovascular disease, 18.76% for coronary heart disease, 16.11% for overall stroke, 14.09% for ischaemic stroke, 18.10% for haemorrhagic stroke, 10.57% for overall respiratory disease, and 12.57% for chronic obstructive pulmonary diseases. The mortality risk and burden were more prominent in the temperate monsoon and subtropical monsoon climatic zones, in specific subgroups (female sex, age ≥75 years, and ≤9 years spent in education), and in cities characterised by higher urbanisations rates and shorter durations of central heating.

Conclusions This nationwide study provides a comprehensive picture of the non-linear associations between ambient temperature and mortality from all natural causes and main cardiorespiratory diseases, as well as the corresponding disease burden that is mainly attributable to moderate cold temperatures in China. The findings on vulnerability characteristics can help improve clinical and public health practices to reduce disease burden associated with current and future abnormal weather.

Footnotes

  • Contributors: RC and PY are joint first authors. HK (kanh{at}fudan.edu.cn) and MZ contributed equally to the correspondence work. RC and PY analysed the data and drafted the manuscript. HK and MZ designed this work and revised the manuscript. LW, CL, YN, WW, YJ, YL, JL, JQ, and JY contributed to data collection. All authors contributed to the development of the manuscript and approved the final draft. HK and MZ are study guarantors. The corresponding authors attest that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

  • Funding: The study was supported by the National Natural Science Foundation of China (91643205 and 91743111), and China Medical Board Collaborating Programme (16-250). The funders were not involved in the research and preparation of the article, including study design; collection, analysis, and interpretation of data; writing of the article; nor in the decision to submit it for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: support from the National Natural Science Foundation of China, and China Medical Board Collaborating Programme for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The institutional review board at the School of Public Health, Fudan University, approved the study protocol (No 2014-07-0523) with a waiver of informed consent. Data were analysed at aggregate level and no participants were contacted.

  • Data sharing: The mortality data can only be applied for through a government data sharing portal (www.phsciencedata.cn/Share/edtShare.jsp). Data on the environment and city characteristics are available on the government’s statistic yearbooks or websites listed in the methods section.

  • The lead authors (HK and MZ) affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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