Long-term exposure to fine particulate constituents and cardiovascular diseases in Chinese adults.

BACKGROUND

Ambient fine particulate matter (PM) has been linked to various cardiovascular disease (CVD) endpoints. However, little is known regarding the health effects of PM constituents. This study aimed to assess the associations of CVD incidence with long-term exposures to PM constituents in China, including black carbon (BC), organic matter (OM), sulfate (SO), nitrate (NO) and ammonium (NH).

METHODS

A nationwide cohort of 14,331 adults were drawn from the China Family Panel Study, a high-quality longitudinal survey initiated from 2010 over 25 provincial regions in China. We used the baseline survey and the ensuing three waves of follow-up data during 2010-2017 to conceive our study cohort. Annual county-level exposures of PM and its constituents for each participant were assessed by aggregating satellite-derived estimates at a monthly time-scale and 1 km-resolution. A directed acyclic graph (DAG) was developed to identify confounding variables. Cox proportional hazards models with time-varying exposures and province-level random intercepts were employed to quantify associations of CVD incidence with long-term exposures to PM and its constituents.

RESULTS

During 84,162.4 person-years' follow-up, a total of 1575 CVD, 953 hypertension and 342 stroke incidents occurred. DAG-based Cox model estimated an hazard ratio (HR) of 1.291 (95% confidence interval: 1.147-1.454) for total CVD and 1.326 (1.151-1.528) for hypertension, associated with per interquartile range (IQR=27.9 μg/m) increase in exposure to PM mass. Elevated CVD risks were also significantly related to several PM constituents, with the largest HRs observed in SO (1.721 [1.517-1.951], IQR = 5.67 μg/m), followed by NH (1.537 [1.341-1.762], IQR = 4.44 μg/m), NO (1.311 [1.128-1.523], IQR = 8.92 μg/m) and BC (1.294 [1.158-1.446], IQR = 2.28 μg/m). No associations were identified between long-term exposures to particulate constituents and incidence of stroke. Associations with PM and constituents (BC, NO, NH and SO) were more pronounced among adults aged over 50 years, and residents in southern region.

CONCLUSIONS

Long-term exposures to PM mass and specific constituents (i.e., BC, NO, NH and SO) were associated with increased risks of total CVD and hypertension incidence in Chinese adults. Findings may have implications for in-depth understandings of biological mechanisms in chronic impacts of ambient PM on cardiovascular health.