• Chika Nishiyama, Taku Iwami, Graham Nichol, Tetsuhisa Kitamura, Atsushi Hiraide, Tatsuya Nishiuchi, Yasuyuki Hayashi, Hiroshi Nonogi, and Takashi Kawamura.
• Kyoto Prefectural University of Medicine School of Nursing, 410 Nakagoryo-cho, Kamigyou-ku, Kyoto 602-0857, Japan.
• Resuscitation. 2011 Aug 1;82(8):1008-12.

ObjectiveLittle 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.MethodsThis 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.ResultsAmong 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.ConclusionBoth 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.Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

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