Impact of Long-Term Cumulative Exposure to Wildfire Smoke PM2.5 on Cardiovascular Hospital Admissions Among Older Adults in the United States
Résumé
Background: As wildfires intensify in a warming climate, prolonged exposure to smoke-derived fine particulate matter (PM2.5) poses significant health risks. However, the cardiovascular impacts of long-term cumulative exposure to smoke PM2.5 remain understudied. Objectives: This study sought to investigate associations between long-term cumulative exposure to wildfire smoke PM2.5 and first cardiovascular disease (CVD) hospitalizations among U.S. Medicare beneficiaries and to assess potential effect modification by sociodemographic factors. Methods: This population-based cohort study analyzed 65.2 million Medicare beneficiaries (aged ≥65 years) across the contiguous United States from 2017 to 2022. Wildfire smoke PM2.5 was estimated with the use of a spatiotemporal model at 10 × 10 km resolution and assigned to beneficiaries' residential ZIP codes. We applied quasi-Poisson regressions to estimate relative risks (RRs) and 95% CIs of CVD hospitalizations for each decile of wildfire smoke PM2.5 concentrations, using exposures below the 1st percentile (0.08 μg/m3) as reference. Results: Three-year average wildfire smoke PM2.5 was significantly associated with increased CVD hospitalization risk. We observed a nonlinear pattern peaking at moderate exposure levels (wildfire smoke PM2.5 concentrations between 0.26 and 0.32 μg/m3) for overall CVD (RR: 1.04; 95% CI: 1.03-1.05), ischemic heart disease (RR: 1.07; 95% CI: 1.06-1.09), and arrhythmias (RR: 1.06; 95% CI: 1.04-1.07). Cerebrovascular hospitalizations showed an increasing trend across exposure levels. Beneficiaries of lower socioeconomic status were potentially more vulnerable. Conclusions: Long-term cumulative wildfire smoke PM2.5 exposure is associated with elevated CVD hospitalization risk, varying by exposure levels and individual characteristics. These findings underscore the need for targeted public health strategies to mitigate cardiovascular risks among older adults with the occurrence of wildfires.