Annual average PM2.5 exposure is associated with mortality in a heart failure cohort: results from the EPA CARES study
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As part of the EPA CARES study, we extracted electronic health records (EHRs) on 41,000 heart failure (HF) patients seen at a University of North Carolina affiliated hospital from 01/01/2004 through 12/31/2016. After data cleaning and restricting to those residing in North Carolina we were left with a study cohort of 37,206 individuals. Over an average follow-up time of 2.25 years (83,895 person-years total follow-up time), we observed 9690 (26.0%) natural cause deaths (non-accidental, non-homicidal deaths). Information on annual average PM2.5 exposure was taken from ground-based monitors operated by the Environmental Protection Agency. Cox proportional hazards models were used to model the association between natural cause mortality and PM2.5 exposure while adjusting for age, sex, race, and Hispanic ethnicity. Results are given in terms of the hazard ratio (HR) per 1 µg/m3 increase in PM2.5 and the associated 95% confidence interval (CI). In CARES, annual average PM2.5 exposure was associated with a substantial elevated mortality risk (HR = 1.24, CI = 1.22, 1.25); results which were consistent when restricting to those within 30 km of a monitoring station (HR = 1.22, CI = 1.21, 1.23). This association was strongest in those with diagnosed HF before the age of 50 (HR = 1.30, CI = 1.26, 1.35). As compared to individuals residing in areas below the National Ambient Air Quality Standard of 12 µg/m3 for PM2.5, individuals in areas exceeding 12 µg/m3 had an elevated mortality risk (HR = 2.75, CI = 2.62, 2.88). Long-term PM2.5 exposure is associated with a substantial mortality risk in individuals with pre-existing HF, particularly those diagnosed before age 50. Residing in areas with annual average PM2.5 above 12 µg/m3 may impart substantial mortality risk for those with HF as compared to residing in areas below this level.