Associations between source-apportioned PM2.5 and 30-day readmissions in heart failure patients
Air pollution exposure is a significant risk factor for morbidity and mortality particularly for those with pre-existing chronic disease. Previous studies have highlighted the risks that long-term particulate matter exposure has for readmissions. However, few studies have evaluated source specific associations particularly among vulnerable patient populations. We used electronic health records from 5,556 heart failure patients diagnosed between July 5, 2004 and December 31, 2010 that were part of the EPA CARES resource in conjunction with modeled source-specific fine particulate matter (PM2.5) to estimate the association between source-specific PM2.5 exposure and 30-day readmissions in heart failure patients. We used zero-inflated mixed effects Poisson models with a random intercept for zip code to model the associations while adjusting for age at diagnosis, year of diagnosis, race, sex, smoking status, and neighborhood socioeconomic status. We undertook several sensitivity analyses to explore the impact of geocoding precision and other factors on associations and expressed associations per interquartile range increase in exposures. We observed associations between 30-day readmissions and gasoline (16.9% increase; 95% confidence = 4.8%, 30.4%), diesel (9.9% increase; 95% confidence interval = 1.7%, 18.7%), and secondary organic carbon (SOC; 20.4% increase; 95% confidence interval = 8.3%, 33.9%) PM2.5. Associations were stable in sensitivity analyses, and most consistently observed among Black and female study participants as well as those in lower income areas and those diagnosed with heart failure at an earlier age. Concentration-response curves indicated a linear association for diesel and SOC and while there was some non-linearity in the gasoline concentration-response curve only the linear component was associated with 30-day readmissions. In conclusion, there appear to be source specific associations between PM2.5 and 30-day readmissions particularly for traffic-related sources. These associations potentially indicate unique toxicity of some sources for readmission risks that should be further explored.