Ambient air pollution and emergency department visits for stroke

Abstract

Background: Many epidemiological studies have shown short-term effects of ambient air pollution on cardiovascular diseases. Several studies have investigated the relationship between air pollutant exposure and stroke but the findings have been inconsistent.Objective: We conducted a time-series study to assess the association between ambient air pollution and emergency department (ED) visits for stroke in Seoul, Republic of Korea.Materials and methods: The ED data from 2005 to 2009 were obtained from the Health Insurance Review and Assessment Service, and the number of ED visits for stroke was 94,539. We used a generalized additive model with Poisson distribution, adjusting for temperature (cubic spline, df=6), relative humidity (cubic spline, df=3), day of the week, and national holidays. The risk was expressed as a RR with one standard deviation increase and its 95% CI. We explored the lag effects with cumulative lag models (lag0-1 to lag0-3). Stratification of age and gender to analyze the differences was conducted and the RRs were estimated. Results: In the same day exposure, the RRs of ED visits for stroke were 1.017 (95% CI, 1.011-1.024) per 12.04 ppb increment of NO2 and 1.013 (1.006-1.020) per 0.24 ppm increment of CO. In lag0-3, the RRs for stroke were 1.006 (1.000-1.013) per 36.70 μg/m3 increment of PM10, 1.012 (1.004-1.020) per 10.04 ppb increment of O3 and 1.009 (1.002-1.016) for CO. In oldest elderly group, significantly positive correlation was found for hemorrhagic stroke in contrast to other age groups and the RR was 1.044 (1.011-1.077) per 10.04 ppb increment of O3 in lag1.Conclusion: Ambient air pollutants are significantly correlated with ED visits for stroke.