BACKGROUND: Weather conditions affect the occurrence of cardiovascular disease. The aim of this study was to investigate the associations between atmospheric conditions including temperature, pressure, and humidity, and the occurrence of out-of-hospital cardiac arrests (OHCAs) with cardiac etiology. METHODS AND RESULTS: This study was a cross-sectional analysis of a prospective cohort that included all persons aged ≥ 18 years with OHCA in Osaka, from 1998 through 2007. The association between the number of daily OHCA events with various atmospheric conditions was analyzed using Poisson regression. A total of 28,806 adult OHCAs were presumed to be of cardiac etiology. The number of OHCAs in 1 day was inversely correlated with the day's mean atmospheric temperature. The regression coefficient was greater on the days under 18°C (r=-0.317, P<0.001) than on days over 18°C (r=-0.088, P<0.001). A positive linear relation was found between the number of OHCAs in 1 day and the day's mean atmospheric pressure (r=0.321, P<0.001). Under 18°C, every 5°C decrease in the daily mean temperature was associated with an 11% (95% confidence interval [CI]: 8-13%) increase in OHCA occurrence in the non-elderly group, and a 16% increase in the elderly group (95% CI: 14-19%). CONCLUSIONS: The occurrence of adult OHCA with cardiac etiology increases with decreasing temperature of the day. Elderly people are more susceptible to severe weather conditions.
BACKGROUND: Weather conditions affect the occurrence of cardiovascular disease. The aim of this study was to investigate the associations between atmospheric conditions including temperature, pressure, and humidity, and the occurrence of out-of-hospital cardiac arrests (OHCAs) with cardiac etiology. METHODS AND RESULTS: This study was a cross-sectional analysis of a prospective cohort that included all persons aged ≥ 18 years with OHCA in Osaka, from 1998 through 2007. The association between the number of daily OHCA events with various atmospheric conditions was analyzed using Poisson regression. A total of 28,806 adult OHCAs were presumed to be of cardiac etiology. The number of OHCAs in 1 day was inversely correlated with the day's mean atmospheric temperature. The regression coefficient was greater on the days under 18°C (r=-0.317, P<0.001) than on days over 18°C (r=-0.088, P<0.001). A positive linear relation was found between the number of OHCAs in 1 day and the day's mean atmospheric pressure (r=0.321, P<0.001). Under 18°C, every 5°C decrease in the daily mean temperature was associated with an 11% (95% confidence interval [CI]: 8-13%) increase in OHCA occurrence in the non-elderly group, and a 16% increase in the elderly group (95% CI: 14-19%). CONCLUSIONS: The occurrence of adult OHCA with cardiac etiology increases with decreasing temperature of the day. Elderly people are more susceptible to severe weather conditions.