The 2023 Canadian Wildfires and Risk of Hospitalization and Mortality Among Hemodialysis Patients in the United...

Smoke plumes from the 2023 Canadian wildfires severely impacted air quality across the Eastern and Midwestern USA. However, a comprehensive health impact assessment is lacking in this large region. We investigated the association between wildfire-related air pollutants and the risk of mortality and hospitalization among hemodialysis patients in 22 heavily impacted states in the Eastern and Midwestern USA.

We conducted a retrospective observational study using a time-stratified case-crossover analysis with a conditional quasi-Poisson model. The study included 52,995 patients with end-stage kidney disease (ESKD) receiving hemodialysis at Fresenius Kidney Care clinics during June and July 2023. The presence of wildfire smoke and fine particulate matter (with aerodynamic diameter < 2.5 microns, PM_2.5) concentrations were assessed using satellite-derived smoke polygons and ground-based monitors. Daily number of all-cause deaths, all-cause hospitalizations, respiratory disease hospitalizations, and cardiovascular disease hospitalizations were counted for each hemodialysis clinic.

The highest daily wildfire-related PM_2.5 concentration observed (251.1 μg/m³) far exceeded the National Ambient Air Quality Standard (35 μg/m³). The presence of wildfire smoke plume was associated with an 18% increase in risk of same day (lag0) all-cause mortality (rate ratio [RR]:1.18; 95% confidence interval [CI], 1.13-1.24) and a 3% increase in risk of all-cause hospitalization (RR:1.03; 95% CI: 1.00-1.07). A 10 μg/m³ increase in wildfire-related PM_2.5 was associated with a 139% increase in same day all-cause mortality (RR: 2.39; 95% CI: 1.79-3.18), and a 33% increase in all-cause hospitalization (RR:1.33; 95% CI: 1.10-1.62).

Our findings suggest that air pollution from the 2023 Canadian wildfires resulted in increased risk of mortality and hospitalization among hemodialysis patients in Eastern and Midwestern USA.