Long-term exposure to fine particulate matter constituents and incident stroke risk among middle-aged and older adults in China: a cohort study
TL;DR
Long-term exposure to PM2.5 constituents is associated with an elevated risk of incident stroke, with black carbon showing the strongest association among the five constituents.
Abstract
Background Although long-term exposure to ambient fine particulate matter (PM2.5) is an established risk factor for stroke, evidence on the detrimental effects of its specific constituents remains limited. This study aimed to investigate the associations between long-term exposure to PM2.5 constituents and incident stroke, and to identify the key contributor. Methods We conducted a nationwide prospective cohort study using data from the China Health and Retirement Longitudinal Study (CHARLS) between 2013 and 2018. Incident stroke cases were identified from CHARLS self-reported physician diagnoses during follow-up interviews. PM2.5 constituent concentration data were derived from the Tracking Air Pollution in China (TAP) dataset, while temperature and relative humidity data were obtained from the European Center for Medium-Range Weather Forecasts Reanalysis v5 (ERA5). 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 incident stroke. Multivariate Cox models and quantile-based g-computation were applied to assess the associations of PM2.5 constituents with incident stroke and to identify the key contributor. Results Over a median follow-up of 5.0 years, 610 incident stroke cases occurred among 8,724 participants. 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%) exhibited the largest weight within the mixture. Stratified analyses revealed that individuals aged over 65 years and residents of southern China were more susceptible. Conclusion Long-term exposure to PM2.5 constituents is associated with an elevated risk of incident stroke, with black carbon showing the strongest association among the five constituents. Older adults and residents of southern China were found to exhibit heightened susceptibility. These findings highlight the importance of mitigating the growing stroke burden through tailored clinical approaches and targeted regulation of carbonaceous emissions, accounting for demographic and regional vulnerabilities.