Seasonal Effect on Association between Atmospheric Pollutants and Hospital Emergency Room Visit for Stroke

Background The relationship between air pollution and stroke is conflicting. This study was conducted to document the relationship between daily changes in atmospheric pollutants and hospital emergency room visits (ERVs) for stroke. Methods Data of daily hospital ERVs for stroke and atmospheric pollutants in Changsha city between 2008 and 2009 were collected. Using a time-stratified bidirectional case-crossover design, we analyzed the association between atmospheric pollutants and stroke incidence in 4 seasons. Results In the single-pollutant model, we found changes in sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and particulate matters (PM 10 ) were significantly associated with cerebral hemorrhage and cerebral infarction ( P 3 increase in SO 2 in autumn was significantly associated with ERVs for both cerebral hemorrhage (odds ratio [OR], 1.166; 95% confidence interval [CI], 1.012-1.343) and cerebral infarction (OR, 1.214; 95% CI, 1.018-1.448). NO 2 in autumn was significantly associated with ERVs for cerebral hemorrhage and infarction with OR = 1.162 (95% CI, 1.005-1.344) and OR = 1.137 (95% CI, 1.011-1.279), respectively. PM 10 in autumn was significantly associated with ERVs for cerebral hemorrhage and infarction with OR = 1.147 (95% CI, 1.045-1.259) and OR = 1.091 (95% CI, 1.019-1.168), respectively. Results of the multipollutant model showed that in autumn after PM 10 and NO 2 adjustment, only a 10-µg/m 3 increase in SO 2 was significantly associated with ERVs for cerebral infarction (OR, 1.158; 95% CI, 1.006-1.333; P 2 , NO 2 , and PM 10 were not associated with ERVs for cerebral hemorrhage ( P  > .05). Conclusions This study demonstrates that the change in atmospheric SO 2 levels in Changsha is significantly associated with the stroke incidence in autumn.