Association between air pollution and incident cardiovascular diseases among a population with cardiovascular-kidney-metabolic syndrome stages 0-3: the first evidence from the China Health and Retirement Longitudinal Study.

BACKGROUND

The longitudinal associations between air pollution exposure and incident cardiovascular diseases (CVDs) among individuals with cardiovascular-kidney-metabolic (CKM) syndrome remains limited. This study aimed to estimate the associations of long-term exposure to air pollution with the incidence of total CVDs, heart disease, and stroke among Chinese individuals with CKM syndrome stages 0-3.

METHODS

This population-based cohort study used data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2018), matching air pollutant data from the China High Air Pollutants dataset. We applied single- and multiple-pollutant Cox proportional hazards model with time-varying to investigate whether annual mean exposure to PM1, PM2.5, PM10, O3, and NO2 affects total CVDs and its major subtypes. Subgroup and mediation analyses were also performed to further evaluate the interactions among these factors.

RESULTS

Among 7400 adults with CKM syndrome stages 0-3, 1611 (21.8%) reported CVD events (1212 heart disease and 551 stroke) during a 7-years follow-up survey. Per 10-μg/m3 increase in PM1, PM2.5, PM10, O3, and NO2 corresponded to a 14.8% (hazard ratio [HR], 1.148 [95% CI, 1.086-1.214]), 9.6% (HR, 1.096 [95% CI, 1.064-1.128]), 6.8% (HR, 1.068 [95% CI, 1.052-1.084]), 2.5% (HR, 1.025 [95% CI, 0.962-1.091]), and 12.4% (HR, 1.124 [95% CI 1.063-1.189]) higher incident risk of CVD, respectively, whereas O3 showed no significant association. We detected significant effect modification by education in the associations of incident CVD and heart disease with PM1, PM2.5, PM10, and NO2 (P interaction <0.05), suggesting that those with lower education level were more vulnerable. Metabolic syndrome partially mediated the association between air pollution exposure and CVD, highlighting its significance in CVDs risk assessment.

CONCLUSIONS

In this nationwide cohort, long-term exposure to PM1, PM2.5, PM10, and NO2 was associated with a higher risk of incident CVD among middle-aged and older Chinese adults with CKM syndrome stages 0-3, which was partially mediated by metabolic syndrome. These findings highlight the potential vulnerability of individuals with lower educational attainment within preclinical CKM syndrome population and underscore the contribution of metabolic syndrome to pollution-related CVD risk.