Association of Short-Term PM2.5 with Hospital Readmissions in Heart Failure Patients in North Carolina, USA

Abstract

Background/Aim: Short-term changes in ambient fine particulate matter (diameter ≤ 2.5 μm, PM2.5) air pollution increase the risk for hospital admission and readmission. Additional research is needed to understand these risks in individuals with underlying cardiovascular disease. Here, we measure the PM2.5-realted readmission risk in heart failure (HF) patients and examine how this risk varies with respect to time following discharge. Methods: The study cohort included 17,674 HF patients (49,835 inpatient hospitalizations) admitted to a University of North Carolina-affiliated hospital between July 2004 and December 2016. Daily ambient PM2.5 was estimated using a neural network with 1km resolution. Time-dependent Cox proportional hazards models estimated the association between daily ambient PM2.5 and the risk of a 30-day readmission (any cause) after adjusting for sex, race, age, prior hospital visits, temperature, relative humidity, length of stay, and discharge day. Time-dependent readmission risk was addressed by examining two time windows: early (1-7d) and late (8-30d) readmissions. Results are expressed as the hazard ratio per 10 μg/m3 increase in same day PM2.5. Results: The 30-day readmission risk associated with a 10 μg/m3 increase in same day PM2.5 was on average increased by 2.8% (95% CI: -0.9-6.6%), but varied based on the time since discharge. PM2.5-realted readmission risks were greatest during the early time period (1-7d), where a 10 μg/m3 increase in PM2.5 was associated with a 6.2% (95% CI: 0.03-12.4%) increased readmission risk. Readmissions occuring 8-30 days after discharge had weaker associations with PM2.5 that included the null (2.8%, 95% CI: -1.4-7.5%). Conclusions: Elevated daily PM2.5 is associated with increased risk of a 30-day hospital readmission, particularly in the first week following hospital discharge. Our results suggest that reducing exposure to PM2.5 could reduce the burden of frequent readmissions on patients and the healthcare system. This abstract does not reflect EPA policy.