Effects of short-term ambient PM2.5 exposure on cardiovascular disease incidence and mortality among U.S. hemodialysis patients: a retrospective cohort study
Background: Ambient PM2.5 is a ubiquitous air pollutant that has demonstrated adverse health impacts in the general population. However, there are subgroups of the population, such as hemodialysis patients, that may be particularly susceptible to the effects of PM2.5 exposure. This study examines associations between short-term PM2.5 exposure and cardiovascular disease (CVD) incidence and mortality among patients receiving maintenance in-center hemodialysis.
Methods: Using the United State Renal Data System (USRDS) registry, we enumerated a cohort of all US adult kidney disease patients who initiated in-center hemodialysis between 1/1/2011 and 12/31/2016. Daily ambient PM2.5 was estimated on a 1 km grid for the entire contiguous US and assigned to cohort members based on the ZIP code of the dialysis clinic. CVD incidence and mortality were ascertained through 2016 based on USRDS records. Discrete time hazards regression was used to estimate the association between PM2.5 exposure and CVD incidence, CVD-specific mortality, and all-cause mortality under 1- and 3-day lags, and 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 comorbidities.
Results: Among 314,079 hemodialysis patients, a 10 µg/m3 increase in the average lag 0-1 daily PM2.5 exposure was associated with CVD incidence [HR: 1.03 (95% CI: 1.02, 1.04)], CVD mortality [1.05 (95% CI: 1.03, 1.08)], and all-cause mortality [1.04 (95% CI: 1.03, 1.06)]. The association was larger for people who initiated dialysis at an older age, while minimal evidence of effect modification was observed across levels of sex, race, or baseline comorbidities.