Air Pollution and Adverse Cardiovascular Events After Coronary Artery Bypass Grafting: A 10-Year Nationwide Study.

BACKGROUND

Increased particulate matter <2.5 μm (PM) air pollution is associated with adverse cardiovascular outcomes. However, its impact on patients with prior coronary artery bypass grafting (CABG) is unknown.

OBJECTIVES

The purpose of this study was to evaluate the association between major adverse cardiovascular events (MACE) (defined as myocardial infarction, stroke, or cardiovascular death) and air pollution after CABG.

METHODS

We linked 26,403 U.S. veterans who underwent CABG (2010-2019) nationally with average annual ambient PM estimates using residential address. Over a 5-year median follow-up period, we identified MACE and fit a multivariable Cox proportional hazard model to determine the risk of MACE as per PM exposure. We also estimated the absolute potential reduction in PM attributable MACE simulating a hypothetical PM lowered to the revised World Health Organization standard of 5 μg/m.

RESULTS

The observed median PM exposure was 7.9 μg/m (IQR: 7.0-8.9 μg/m; 95% of patients were exposed to PM above 5 μg/m). Increased PM exposure was associated with a higher 10-year MACE rate (first tertile 38% vs third tertile 45%;  < 0.001). Adjusting for demographic, racial, and clinical characteristics, a 10 μg/m increase in PM resulted in 27% relative risk for MACE (HR: 1.27, 95% CI: 1.10-1.46;  < 0.001). Currently, 10% of total MACE is attributable to PM exposure. Reducing maximum PM to 5 μg/m could result in a 7% absolute reduction in 10-year MACE rates.

CONCLUSIONS

In this large nationwide CABG cohort, ambient PM air pollution was strongly associated with adverse 10-year cardiovascular outcomes. Reducing levels to World Health Organization-recommended standards would result in a substantial risk reduction at the population level.