title: Association of out-of-hospital cardiac arrest with prior activity and ambient temperature.
abstract: OBJECTIVE
  Little is known about triggers of sudden cardiac arrest. This study aimed to analyze the association of the occurrence of out-of-hospital cardiac arrest (OHCA) with patient activities just before the arrest and ambient temperature as one of the major environmental factors.
  
  
  METHODS
  This prospective, population-based cohort study enrolled all person aged 18 years or older with OHCA of presumed cardiac origin in Osaka Prefecture, Japan, from 2005 through 2007. Patient activities before arrest were divided into six categories: sleeping, bathing, working, exercising, non-specific activities, and unknown. Age-adjusted annual incidence rate of OHCA according to their prior activity and an hourly event rate in each activity by temperature were calculated.
  
  
  RESULTS
  Among 19,303 OHCAs, 10,723 were presumed to be of cardiac etiology. The event rate of OHCA was 6.22, 54.49, 1.15, and 10.11 per 10,000,000 population per hour for sleeping, bathing, working, and exercising, respectively. Among patients who suffered OHCA during bathing, the event rate of OHCA per 10,000,000 per hour increased with decreasing temperature from 18.27 (≥25.1°C) to 111.42 (≤5.0°C) (odds ratio [OR] for 1°C increase in temperature, 0.915; 95% confidence interval [CI], 0.907-0.923), while it was almost constant among those who were working (OR for 1°C increase, 0.994; 95% CI, 0.981-1.007) or exercising (OR for 1°C increase, 1.004; 95% CI, 0.971-1.038) before arrest.
  
  
  CONCLUSIONS
  Both activities before cardiac arrest and ambient temperature were associated with the occurrence of OHCA. Preventive measures against OHCA should be enveloped considering these behavioral and environmental factors.
authors.affiliation: Kyoto Prefectural University of Medicine School of Nursing, 410 Nakagoryo-cho, Kamigyou-ku, Kyoto 602-0857, Japan.
authors.forename: Chika
authors.initials: C
authors.lastname: Nishiyama
authors.forename: Taku
authors.initials: T
authors.lastname: Iwami
authors.forename: Graham
authors.initials: G
authors.lastname: Nichol
authors.forename: Tetsuhisa
authors.initials: T
authors.lastname: Kitamura
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hiraide
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Nishiuchi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonogi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawamura
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000704:Analysis of Variance; D004632:Emergency Medical Services / Q000458:organization & administration; D004777:Environment; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology*; D016012:Poisson Distribution; D011446:Prospective Studies; D012307:Risk Factors; D012621:Seasons; D015996:Survival Rate; D013696:Temperature