title: Spatiotemporal variation in heat-related out-of-hospital cardiac arrest during the summer in Japan.
abstract: BACKGROUND
  Although several studies have reported the impacts of extremely high temperature on cardiovascular diseases, few studies have investigated the spatiotemporal variation in the incidence of out-of-hospital cardiac arrest (OHCA) due to extremely high temperature in Japan.
  
  
  METHODS
  Daily OHCA data from 2005 to 2014 were acquired from all 47 prefectures of Japan. We used time-series Poisson regression analysis combined with a distributed lag non-linear model to assess the temporal variability in the effects of extremely high temperature on OHCA incidence in each prefecture, adjusted for time trends. Spatial variability in the relationships between extremely high temperature and OHCA between prefectures was estimated using a multivariate random-effects meta-analysis.
  
  
  RESULTS
  We analyzed 166,496 OHCA cases of presumed cardiac origin occurring during the summer (June to September) that met the inclusion criteria. The minimum morbidity percentile (MMP) was the 51st percentile of temperature during the summer in Japan. The overall cumulative relative risk at the 99th percentile vs. the MMP over lags 0-10days was 1.21 (95% CI: 1.12-1.31). There was also a strong low temperature effect during the summer periods. No substantial difference in spatial or temporal variability was observed over the study period.
  
  
  CONCLUSIONS
  Our study demonstrated spatiotemporal homogeneity in the risk of OHCA during periods of extremely high temperature between 2005 and 2014 in Japan. Our findings suggest that public health strategies for OHCA due to extremely high temperatures should be finely adjusted and should particularly account for the unchanging risk during the summer.
authors.affiliation: Department of Health Communication, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Electronic address: onozukad@hcam.med.kyushu-u.ac.jp.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Onozuka
authors.affiliation: Department of Health Communication, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Electronic address: hagihara@hsmp.med.kyushu-u.ac.jp.
authors.forename: Akihito
authors.initials: A
authors.lastname: Hagihara
mesh_terms: D000368:Aged; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D009017:Morbidity; D015999:Multivariate Analysis; D017711:Nonlinear Dynamics; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology*
keywords: Environmental medicine; Epidemiology; Heart arrest; Heat; Statistical analysis; Sudden death