Association between ambient air pollution and ischemic stroke hospitalization: A multicenter case-crossover study in Tianjin, China

Objective: This study aims at exploring the associations between six major ambient air pollutants, including PM2.5, PM10, NO2, SO2, CO, O3, and IS incidence in a Chinese megacity (Tianjin), and finding out susceptible populations, to provide insights for public IS prevention in areas facing relatively higher level of air pollution and heavier IS burden. Method: We collected IS admissions data across 5 hospitals in Tianjin from January 1, 2016 to December 31, 2019. The daily mean concentrations of ambient air pollutants were used as exposure parameters. We applied a time-stratified case-crossover design combined with quasi-poisson regression to examine short term effects of air pollution on IS hospitalizations and performed subgroup analyses stratified by gender, age, and season. Results: 75132 IS cases were enrolled finally. We found that increases of 10 mu g/m3 in PM2.5 and NO2 were associated with 0.26 %(95 % CI: 0.01 %-0.53 %) and 1.05 % (95 % CI: 0.34 %-1.76 %) increases in IS hospitalization at the same day (Lag0 day) respectively, but no lag effects were observed in the single-day lag structure. And the cumulative lag effects of PM2.5 and NO2 were only observed at lag01 day with the percentage increases of IS for 10 mu g/m3 of their concentrations being 0.36 %(95 % CI: 0.04 %-0.68 %) and 1.21 %(95 % CI: 0.43 %-2.04 %). The effects were more pronounced in the male and younger populations for PM2.5 and NO2 in the warm season, and a positive association was also observed between PM10 and IS in the younger group. As for SO2, CO and O3, no statistically significant associations were found between them and IS. Conclusion: Our findings suggested that short-term exposures to PM2.5, NO2, PM10 increase the risk of IS hospitalizations, especially in the male and younger populations. Reducing targeted pollution emission may have significant public health effects in reducing IS burden.