Air Pollution as a Risk Factor of Emergency Visit for Asthma Attack in Asthmatics

Abstract

BACKGROUND: Many epidemiological studies have suggested the association between air pollution and asthma, but there is little research on asthma attack in Republic of Korea. OBJECTIVES: The purpose of this study was to examine the association between air pollution and asthma attack among asthmatics. METHODS: We conducted a time-series study to evaluate the risk of emergency department (ED) visits for asthma attack related to air pollutants. ED data was obtained from Health Insurance Review & Assessment Service from 2005 to 2009 in Seoul. Asthma attack cases were defined as asthmatic ED visits in those who had =1 hospitalization or =2 outpatient visits for asthma during 3years before the ED visit. Air pollutants included SO2, PM10, O3, NO2, and CO, measured by automatic monitoring system. We used a generalized additive model (GAM) with Poisson distribution with the adjustment for date, temperature (df=30), and relative humidity (df=15) as spline variables. The day of week and holiday were included as parametric variables in the model. We used single lag models (lag0 to lag7), and cumulative lag models were constructed by averaging concentrations on the day of the visit and the previous days (lag0-1 to lag0-7). The concentrations of air pollutants were standardized, and the risk was expressed as percent change (%) of relative risk and its 95% confidence interval (95% CI). RESULTS: 27,896 asthma attack cases were observed during the study period (1,826 days). The risk of ED visits for asthma attack increased by 3.5% (95% CI, 1.7-5.4%) with the increase of PM10 (standard deviation, 36.8?/?) in lag0, and the statistical significance remained for lag1 and lag2 models. Increased risks of ED visits were observed in lag0-2 model for PM10 (5.2%; 95% CI, 3.8-6.6%) and lag0-7 model for NO2 (6.0%; 95% CI, 3.7-8.4%). CONCLUSIONS: PM10, NO2 were positively associated with ED visits for asthma attack.