Ambient air pollution and out-of-hospital cardiac arrest

Background: Sudden cardiac arrest is a leading cause of cardiovascular death. This study aimed at investigating the impact of short-term exposure to air pollutants on the incidence of OHCA. Methods: We identified OHCA cases that occurred in Seoul between 2006 and 2013 from the nationwide emergency medical service database. The association of the daily incidence of OHCA with air pollutants including PM2.5 (particles <= 2.5 mu m in aerodynamic diameter), PM10, CO, O-3, NO2, and SO2 was analyzed with the use of time-series and case-crossover analyses. Results: A total of 21,509OHCAs of presumed cardiac origin were identified. An elevation in PM2.5 by 10 mu g/m(3) at a moving average of lag 1 and 2 days was shown to increase the risk of OHCA by 1.30% (95% confidence intervals, 0.20-2.41%). An exposure-response relationship was present: the risk of OHCA increased significantly with even a mild elevation of PM2.5 (10-15 mu g/m(3)) and further increased with higher levels. While PM10, NO2, CO, and SO2 also showed significant associations with OHCA in single-pollutant models, only PM2.5 remained significant after adjustment for other pollutants. Subgroup analyses showed male sex, advanced age, hypertension, diabetes, heart disease, and history of stroke were risk factors for OHCA in response to elevations in PM2.5. Conclusions: This study showed that increased ambient levels of PM2.5 were significantly associated with increased risk of OHCA within 1 to 2 days of exposure, which had a dose-response relationship. Subjects with conventional cardiovascular risk factors were more susceptible to harm of PM2.5. (C) 2015 Elsevier Ireland Ltd. All rights reserved.