Short-term PM2.5 exposure and early-readmission risk: a retrospective cohort study in North Carolina heart failure patients

Am Heart J. 2022 Jun;248:130-138. doi: 10.1016/j.ahj.2022.02.015. Epub 2022 Mar 7.


Background: Short-term changes in ambient fine particulate matter (PM2.5) increase the risk for unplanned hospital readmissions. However, this association has not been fully evaluated for high-risk patients or examined to determine if the readmission risk differs based on time since discharge. Here we investigate the relation between ambient PM2.5 and 30-day readmission risk in heart failure (HF) patients using daily time windows and examine how this risk varies with respect to time following discharge.

Methods: We performed a retrospective cohort study of 17,674 patients with a recorded HF diagnosis between 2004 and 2016. The cohort was identified using the EPA CARES electronic health record resource. The association between ambient daily PM2.5 (μg/m3) concentration and 30-day readmissions was evaluated using time-dependent Cox proportional hazard models. PM2.5 associated readmission risk was examined throughout the 30-day readmission period and for early readmissions (1-3 days post-discharge). Models for 30-day readmissions included a parametric continuous function to estimate the daily PM2.5 associated readmission hazard. Fine-resolution ambient PM2.5 data were assigned to patient residential address and hazard ratios are expressed per 10 μg/m3 of PM2.5. Secondary analyses examined potential effect modification based on the time after a HF diagnosis, urbanicity, medication prescription, comorbidities, and type of HF.

Results: The hazard of a PM2.5-related readmission within 3 days of discharge was 1.33 (95% CI 1.18-1.51). This PM2.5 readmission hazard was slightly elevated in patients residing in non-urban areas (1.43, 95%CI 1.22-1.67) and for HF patients without a beta-blocker prescription prior to the readmission (1.35; 95% CI 1.19-1.53).

Conclusion: Our findings add to the evidence indicating substantial air quality-related health risks in individuals with underlying cardiovascular disease. Hospital readmissions are key metrics for patients and providers alike. As a potentially modifiable risk factor, air pollution-related interventions may be enacted that might assist in reducing costly and burdensome unplanned readmissions.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aftercare
  • Cohort Studies
  • Environmental Exposure / adverse effects
  • Environmental Exposure / analysis
  • Heart Failure* / chemically induced
  • Heart Failure* / epidemiology
  • Heart Failure* / therapy
  • Humans
  • North Carolina / epidemiology
  • Particulate Matter / adverse effects
  • Particulate Matter / analysis
  • Patient Discharge
  • Patient Readmission*
  • Retrospective Studies


  • Particulate Matter