Short-term effects of ambient oxidation, and its interaction with fine particles on first-ever stroke: A national...

Stroke is a significant global cause of disability and death, and its burden has been on the rise, while ambient air pollution has been conclusively linked to stroke incidence. However, knowledge about effects of atmospheric oxidation on stroke and its interactions with fine particles (PM_2.5) are still limited. In this study, we investigated the short-term effects of ambient NO₂, O₃, and their combined oxidation (O_wt) on first-ever stroke, based on data from the China National Stroke Screening Survey (CNSSS) conducted from 2013 to 2015. We found significant association between ambient NO₂ exposure at lag0 day with first-ever stroke, with a 13.1 % (95 % CI: 3.5 %, 23.6 %) increase in the first-ever stroke risk per 10 μg/m³ exposure. We also found a significant interaction between NO₂ and PM_2.5 (p < 0.05): first-ever stroke risk increased 23.8 % (95 % CI: 9.6 %, 39.8 %) per 10 μg/m³ NO₂ exposure in population exposed to higher PM_2.5 concentrations, while no significant association was found in population exposed to lower PM_2.5 concentrations. The results of stratified analyses indicated that physical inactivity enhanced the detrimental effects of O₃ and O_wt exposure, while smoking and transient ischemic attack (TIA) history enhanced the detrimental effects of NO₂ exposure. However, TIA history appeared to mitigate the adverse effects of O₃ exposure. This study is helpful to better understand the impact of ambient oxidation on stroke, as well as its interaction with PM_2.5, and has implications for policies and standards for atmospheric protection and governance.