Joint Associations of Short-Term Exposure to Ambient Air Pollutants with Hospital Admission of Ischemic Stroke

Background: Studies have estimated the associations of short-term exposure to ambient air pollution with ischemic stroke. However, the joint associations of ischemic stroke with air pollution as a mixture remain unknown. Methods: We employed a time-stratified case–crossover study to investigate 824,808 ischemic stroke patients across China. We calculated daily mean concentrations of particulate matter with an aerodynamic diameter ≤2.5 μm (PM 2.5 ), maximum 8-h average for O 3 (MDA8 O 3 ), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and carbon monoxide (CO) across all monitoring stations in the city where the IS patients resided. We conducted conditional logistic regression models to estimate the exposure–response associations. Results: Results from single-pollutant models showed positive associations of hospital admission for ischemic stroke with PM 2.5 (excess risk [ER] = 0.38%, 95% confidence interval [CI]: 0.29% to 0.47%, for 10 μg/m 3 ), MDA8 O 3 (ER = 0.29%, 95% CI: 0.18% to 0.40%, for 10 μg/m 3 ), NO 2 (ER = 1.15%, 95% CI: 0.92% to 1.39%, for 10 μg/m 3 ), SO 2 (ER = 0.82%, 95% CI: 0.53% to 1.11%, for 10 μg/m 3 ) and CO (ER = 3.47%, 95% CI: 2.70% to 4.26%, for 1 mg/m 3 ). The joint associations (ER) with all air pollutants (for interquartile range width increases in each pollutant) estimated by the single-pollutant model was 8.73% and was 4.27% by the multipollutant model. The joint attributable fraction of ischemic stroke attributable to air pollutants based on the multipollutant model was 7%. Conclusions: Short-term exposures to PM 2.5 , MDA8 O 3 , NO 2 , SO 2 , and CO were positively associated with increased risks of hospital admission for ischemic stroke. The joint associations of air pollutants with ischemic stroke might be overestimated using single-pollutant models. See video abstract at, http://links.lww.com/EDE/C8.