Long-term exposure to ambient fine particulate matter chemical composition and in-hospital case fatality among patients with stroke in China

Background There is little evidence on the association between PM2.5 chemical components and fatality among hospitalized stroke patients.Methods This study used an inpatient discharge database from 2013 to 2019 in four provinces (Sichuan, Shanxi, Guangxi, and Guangdong) in China. Annual average exposure to PM2.5 and its five chemical components [black carbon (BC), organic matter (OM), sulphate (SO2-4 ), nitrate (NO-3), and ammonium (NH+ 4 )] were estimated using bilinear interpolation at patient's residential address. Mixed-effects logistic regression models were conducted to estimate the odds ratios (ORs). Counterfactual analyses were used to estimate the population attributable burden (PAF).Findings Among 3,069,093 hospitalized patients with stroke, each interquartile (IQR) increment in PM2.5 and its chemical components was significantly associated with stroke fatality: the ORs were 1.137 [95% confidence interval (CI): 1.118-1.157; IQR: 15.14 pg/m3] for PM2.5, 1.108 (95% CI: 1.091-1.126; IQR: 0.71 pg/m3) for BC, 1.086 (95% CI: 1.069-1.104; IQR: 3.47 pg/m3) for OM, and 1.065 (95% CI: 1.048-1.083; IQR: 2.81 pg/m3) for SO2-4. We did not find significant associations for NO-3 (OR: 0.991, 95% CI: 0.975-1.008; IQR: 3.30 pg/m3). The associations were larger among patients with ischemic stroke than those with hemorrhagic stroke. The PAFs were 10.6% (95% CI: 9.1-12.2%) for BC, 9.9% (95% CI: 8.2-11.7%) for OM, and 6.6% (4.9-8.3%) for SO2- 4 .Interpretation Ambient BC, OM, and SO2-4 might be important risk factors for stroke fatality. The findings advocate the need to develop tailored guidelines for PM chemical components and curb the emissions of the most hazardous chemical components.