Association of Long-Term Exposure to Ambient Fine Particulate Matter with Atherosclerotic Cardiovascular Disease Incidence Varies across Populations with Different Predicted Risks: The China-PAR Project

Previousstudies have established a significant link between ambientfine particulate matter (PM2.5) exposure and atheroscleroticcardiovascular disease (ASCVD) incidence, but whether this associationvaries across populations with different predicted ASCVD risks wasuncertain previously. We included 109,374 Chinese adults without ASCVDat baseline from the Prediction for Atherosclerotic CardiovascularDisease Risk in China (China-PAR) project. We obtained PM2.5 data of participants' residential address from 2000 to 2015using a satellite-based spatiotemporal model. Participants were classifiedinto low-to-medium and high-risk groups according to the ASCVD 10-yearand lifetime risk prediction scores. Hazard ratios (HRs) and 95% confidenceintervals (CIs) for PM2.5 exposure-related incident ASCVD,as well as the multiplication and additive interaction, were calculatedusing stratified Cox proportional hazard models. The additive interactionbetween risk stratification and PM2.5 exposure was estimatedby the synergy index (SI), the attributable proportion due to theinteraction (API), and the relative excess risk due to interaction(RERI). Over the follow-up of 833,067 person-years, a total of 4230incident ASCVD cases were identified. Each 10 & mu;g/m(3) increment of PM2.5 concentration was associated with18% (HR: 1.18; 95% CI: 1.14-1.23) increased risk of ASCVD inthe total population, and the association was more pronounced amongindividuals having a high predicted ASCVD risk than those having alow-to-medium risk, with the HR (95% CI) of 1.24 (1.19-1.30)and 1.11 (1.02-1.20) per 10 & mu;g/m(3) incrementin PM2.5 concentration, respectively. The RERI, API, andSI were 1.22 (95% CI: 0.62-1.81), 0.22 (95% CI: 0.12-0.32),and 1.37 (95% CI: 1.16-1.63), respectively. Our findings demonstratea significant synergistic effect on ASCVD between ASCVD risk stratificationand PM2.5 exposure and highlight the potential health benefitsof reducing PM2.5 exposure in Chinese, especially amongthose with high ASCVD risk. Thesusceptible population for cardiovascular health effectsrelated to PM2.5 was uncertain. This study found higherPM(2.5)-related ASCVD risk among individuals having a highASCVD risk score, with great implications for policymaking.