Association between Long-Term Ambient PM2.5 Exposure and Cardiovascular Outcomes among U.S. Hemodialysis Patients

Abstract

Background and Aim: Ambient PM2.5 is a ubiquitous air pollutant with established adverse cardiovascular (CV) effects. However, quantitative estimates of PM2.5 exposure associations on CV outcomes in susceptible populations are limited. This study assessed the impact of long-term PM2.5 on CV events and cardiovascular disease (CVD)-specific mortality among patients receiving maintenance in-center hemodialysis (HD). Methods: We conducted a retrospective cohort study with 314,079 adult kidney failure patients initiating HD between 2011 and 2016 identified from the United State Renal Data System. Estimated daily ZIP code-level PM2.5 concentrations were used to calculate each participant’s annual-average PM2.5 exposure based on the dialysis clinics visited during the 365 days prior to the outcome. CV event and CVD-specific mortality were ascertained based on ICD-9/ICD-10 diagnostic codes and recorded cause of death from form 2746. Discrete time hazards models were used to estimate hazards ratios (HRs) per 1 µg/m3 in annual-average PM2.5 adjusting for temperature, humidity, day of the week, season, age at baseline, race, employment status, and geographic region. Effect measure modification was assessed for age, sex, race, and baseline comorbidities. Results: Annual-average PM2.5 of 1 µg/m3 was associated with increased hazard rates in CV events (HR: 1.02, 95% CI: 1.01, 1.02) and CVD-specific mortality (1.02, 95% CI: 1.02, 1.03). The association was more pronounced for people who initiated dialysis at an older age, had COPD at baseline, or were Asian. Evidence of effect modification was also observed across strata of race, and other baseline comorbidities. Conclusions: Long-term ambient PM2.5 exposure was positively associated with CV outcomes among patients receiving maintenance in-center HD. Patients who had advanced age, COPD, or reported to be Asian, appeared to be more susceptible to long-term PM2.5 adverse effects. Keywords: Air pollution, long-term, vulnerable population, dialysis patients