title: Ambient temperature and emergency department visits: Time-series analysis in 12 Chinese cities.
abstract: BACKGROUND
  The association between ambient temperature and mortality has been well documented worldwide. However, limited data are available on nonfatal health outcomes, such as emergency department visits (EDVs), particularly from China.
  
  
  OBJECTIVE
  To examine the temperature-EDV association in 12 Chinese cities; and to assess the modification effects by region, gender and age.
  
  
  METHODS
  Daily meteorological data and non-accidental EDVs were collected during 2011-2014. Poisson regression with distributed lag non-linear model was applied to examine the temperature-lag-EDV association in each city. The effect estimates were pooled using multivariate meta-analysis at the national and regional level. Stratified analyses were performed by gender and age-groups. Sensitivity analyses adjusting for air pollution and relative humidity were conducted.
  
  
  RESULTS
  A total of 4,443,127 EDVs were collected from the 12 cities. Both cold and hot temperatures were associated with increased risk of EDVs, with minimum-mortality temperature located at 64th percentile of temperature. The effect of cold temperature appeared on day 2 and persisted until day 30, causing a cumulative relative risk (RR) of 1.80 (1.54, 2.11). The effect of hot temperature appeared immediately and lasted until day 3, with a cumulative RR of 1.15 (1.03, 1.29). The effect of temperature on EDVs was similar in male and female but was attenuated with increasing age. The effect of cold temperature on EDVs was greater in southern areas of the country whereas the hot effect was greater in northern cities. The association was robust to a large range of sensitivity analyses.
  
  
  CONCLUSIONS
  In China, there is a U-shaped association between temperature and risk of EDVs that is independent of air pollution and humidity. The temperature-EDV association varies with latitude and age-groups but is not affected by gender. Forecasting models for hospital emergency departments may be improved if temperature is included as an independent predictor.
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, 288 Herston Road, Brisbane, 4006, Queensland, Australia.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: Department of Respiratory and Critical Care Medicine, China-Japan Friendship Hospital, 2 East Yinghua Road, Beijing 100029, China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute for Disease Control and Prevention, Academy of Military Medical Science, 20 East Road, Fengtai District, Beijing, 102206, China.
authors.forename: Wenyi
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, 288 Herston Road, Brisbane, 4006, Queensland, Australia.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Li
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, 288 Herston Road, Brisbane, 4006, Queensland, Australia.
authors.forename: Gongbo
authors.initials: G
authors.lastname: Chen
authors.affiliation: First Affiliated Hospital of Guangxi Medical University, 6 Shuangyong Road, Nanning, 530021, Guangxi, China.
authors.forename: Yanbin
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Shenzhen People's Hospital, 1017 North Dongmen Road, Shenzhen, 518020, Guangdong, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Qiu
authors.affiliation: Respiratory and Critical Care Department, Sir Run Run Shaw Hospital, Zhejiang University, 3 East Qingchun Road Hangzhou, 310016, Zhejiang, China.
authors.forename: Kejing
authors.initials: K
authors.lastname: Ying
authors.affiliation: Qingdao Municipal Hospital, 1 Jiaozhou Road, Qingdao, 266011, Shandong, China.
authors.forename: Huaping
authors.initials: H
authors.lastname: Tang
authors.affiliation: First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu, China.
authors.forename: Jian-An
authors.initials: JA
authors.lastname: Huang
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, 288 Herston Road, Brisbane, 4006, Queensland, Australia.
authors.forename: Gail
authors.initials: G
authors.lastname: Williams
authors.affiliation: School of Public Health, Curtin University, Kent Street, Perth, 6102, Western Australia, Australia.
authors.forename: Rachel
authors.initials: R
authors.lastname: Huxley
authors.affiliation: Division of Epidemiology and Biostatistics, School of Public Health, University of Queensland, 288 Herston Road, Brisbane, 4006, Queensland, Australia. Electronic address: y.guo1@uq.edu.au.
authors.forename: Yuming
authors.initials: Y
authors.lastname: Guo
mesh_terms: D017677:Age Distribution; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects / Q000706:statistics & numerical data; D001272:Atmosphere; D002681:China; D002947:Cities / Q000706:statistics & numerical data*; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D006801:Humans; D006813:Humidity; D017711:Nonlinear Dynamics; D010126:Ozone / Q000032:analysis; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D012737:Sex Factors; D013696:Temperature; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone
keywords: Ambient temperature; China; Emergency department visits; Multicity study; Non-linear relationship