Long-term exposure to PM2.5 constituents and incident stroke risk among middle-aged and older adults in China

BackgroundWhile long-term exposure to ambient fine particulate matter (PM2.5) is increasingly recognized as a risk factor for stroke, evidence regarding the detrimental effects of its specific constituents remains limited. MethodsWe conducted a nationwide prospective cohort study using data from the China Health and Retirement Longitudinal Study (CHARLS) between 2013 and 2018. Individual records were matched with environmental exposure data to quantify the associations between specific PM2.5 constituents (sulfate, nitrate, ammonium, organic matter, and black carbon) and the incidence of stroke. We utilized multivariate Cox models to assess the associations between PM2.5 constituents and incident stroke, and employed the Quantile-based g-computation model to identify the key contributor among PM2.5 constituents. ResultsAmong 8724 participants enrolled in this study, 610 individuals developed stroke during a median follow-up period of 5.0 years. All five constituents were significantly associated with stroke onset, the adjusted hazard ratios (95% confidence interval [CI]) for each interquartile range increase were 1.55 (95% CI: 1.35-1.79) for PM2.5, 1.55 (95% CI: 1.34-1.79) for sulfate, 1.37 (95% CI: 1.18-1.59) for nitrate, 1.42 (95% CI: 1.24-1.63) for ammonium, 1.59 (95% CI: 1.40-1.80) for organic matter, and 1.77 (95% CI: 1.54-2.03) for black carbon, respectively. In the joint effect analysis, black carbon (28.6%) emerged as the primary contributor, followed by organic matter (21.7%) and sulfate (20.4%). Stratified analyses revealed that individuals aged over 65 years and residents of southern China were more susceptible. ConclusionsLong-term exposure to PM2.5 constituents is associated with an elevated risk of incident stroke, with black carbon being the primary contributor. Implementing tailored clinical management and targeted regulations on the emissions of carbonaceous components could potentially alleviate the escalating burden of stroke.