Association Between Long-term Ambient PM Exposure and Cardiovascular Outcomes Among US Hemodialysis Patients.

RATIONALE & OBJECTIVE: Ambient PM (particulate matter with a diameter of 2.5 microns) is a ubiquitous air pollutant with established adverse cardiovascular (CV) effects. However, quantitative estimates of the association between PM exposure and CV outcomes in the setting of kidney disease are limited. This study assessed the association of long-term PM exposure with CV events and cardiovascular disease (CVD)-specific mortality among patients receiving maintenance in-center hemodialysis (HD).

STUDY DESIGN

Retrospective cohort study.

SETTINGS & PARTICIPANTS: 314,079 adult kidney failure patients initiating HD between 2011 and 2016 identified from the US Renal Data System.

EXPOSURE

Estimated daily ZIP code-level PM concentrations were used to calculate each participant's annual average PM exposure based on the dialysis clinics visited during the 365 days before the outcome.

OUTCOME

CV event and CVD-specific mortality were ascertained based on ICD-9/ICD-10 diagnostic codes and recorded cause of death from Centers for Medicare & Medicaid Services form 2746.

ANALYTICAL APPROACH

Discrete time hazards models were used to estimate hazards ratios per 1 μg/m greater annual average PM, 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

Each 1 μg/m greater annual average PM was associated with a greater rate of CV events (HR, 1.02 [95% CI, 1.01-1.02]) and CVD-specific mortality (HR, 1.02 [95% CI, 1.02-1.03]). The association was more pronounced for people who initiated dialysis at an older age, had chronic obstructive pulmonary disease (COPD) at baseline, or were Asian. Evidence of effect modification was also observed across strata of race, and other baseline comorbidities.

LIMITATIONS

Potential exposure misclassification and unmeasured confounding.

CONCLUSIONS

Long-term ambient PM exposure was associated with CVD outcomes among patients receiving maintenance in-center HD. Stronger associations between long-term PM exposure and adverse effects were observed among patients who were of advanced age, had COPD, or were Asian.

PLAIN-LANGUAGE SUMMARY: Long-term exposure to air pollution, also called PM, has been linked to adverse cardiovascular outcomes. However, little is known about the association of PM and outcomes among patients receiving dialysis, who are individuals with high cardiovascular disease burdens. We conducted an epidemiological study to assess the association between the annual PM exposure and cardiovascular events and death among patients receiving regular outpatient hemodialysis in the United States between 2011 and 2016. We found a higher risk of heart attacks, strokes, and related events in patients exposed to higher levels of air pollution. Stronger associations between air pollution and adverse health events were observed among patients who were older at the start of dialysis, had chronic obstructive pulmonary disease, or were Asian. These findings bolster the evidence base linking air pollution and adverse health outcomes and may inform policy makers and clinicians.