PM2.5 and 30-Day Readmission in Medicare Beneficiaries with Alzheimer's Disease and Related Dementias: Effect Modification by Neighborhood Green and Blue Space.

Abstract

Hospital readmissions are a major concern among people living with Alzheimer's disease and related dementias (ADRD), contributing to substantial burden on patients, caregivers, and health care systems. We evaluated whether short-term exposure to fine particulate matter (PM_2.5) was associated with 30-day all-cause readmission among older adults with ADRD and whether residential green and blue space modified this association. We conducted a nationwide time-stratified case-crossover study using Medicare fee-for-service inpatient claims from 2000 to 2016 in the contiguous United States. We identified 30-day all-cause readmissions following the first index admission with ADRD. Daily modeled PM_2.5 concentrations were linked to residential ZIP Codes, and exposure windows up to lag 2 days were examined. Measures of green and blue space were derived from Landsat and Google Street View data. Conditional logistic regression was used to estimate associations between PM_2.5 and readmission with interaction terms used to evaluate effect modification by levels of green and blue space. Among 6,098,836 beneficiaries with an index admission with ADRD, 759,128 (12.4%) experienced a 30-day all-cause readmission. An interquartile range (IQR; 7.2 μg/m³) increase in PM_2.5 averaged over lag 0 to 2 days was associated with a higher risk of readmission (odds ratio: 1.010; 95% confidence interval: 1.006, 1.015). Associations were higher for beneficiaries with longer intervals to readmission (>7 days). Effect modification by green or blue space was not conclusive. These findings suggest that short-term PM_2.5 exposure may increase the risk of 30-day all-cause hospital readmission among Medicare beneficiaries with ADRD. Reducing ambient PM_2.5 exposure may help prevent avoidable readmissions and lessen burden on patients, caregivers, and health care systems.