Respiratory
Impact of the 2020 ‘Gigafire’ on in-hospital mortality among respiratory failure patients in the western United States: an interrupted time-series analysis Katie Feng* Kathleen Lynch Katie Feng Mari Armstrong-Hough
Background: In 2020, the western United States experienced the most extreme wildfire season on record and produced California’s first ‘gigafire’, buring over one million acres and dispersing smoke plumes across the region. Temporal trends suggest hospital admissions coincide with peak wildfire smoke exposure, yet mortality among those with pre-existing respiratory failure remains poorly understood.
Methods: We analyzed acute respiratory distress syndrome (ARDS) and respiratory failure hospitalizations (RF) between January 1, 2017- December 30, 2020 using Premier Hospital Alliance data, and used a high-resolution wildland fire smoke dataset to estimate daily county-level PM2.5 concentrations. We applied an interrupted time-series design, defining the event as September 2020 (the gigafire’s peak smoke intensity; PM2.5 >300 µg/m³). Mixed-effects logistic regression estimated odds ratios of daily in-hospital mortality during smoke exposure and non-exposure periods, adjusting for seasonal trends (i.e., influenza, COVID-19), patient characteristics (i.e., age, race/ethnicity, gender, BMI, length of hospitalization), and insurance status.
Results: 162 hospitals were exposed to excessive wildfire smoke during the study period; those with ARDS (n=7,588) had a mortality rate (MR) of 47.3%, followed by acute RF (n=483,037; MR 13.9%) and chronic RF (n=7,884; MR 2.6%). During the gigafire smoke event, 1,666 patients (8.9%) died before discharge. In the final adjusted model, the odds of in-hospital mortality increased by 31.6% during the gigafire smoke event (OR 1.32, 95% CI 1.24–1.42) and by 13.2% after the event (OR 1.13, 95% CI 1.12–1.14).
Conclusion: The 2020 Gigafire smoke event was associated with increased in-hospital mortality among respiratory failure patients after adjusting for seasonal trends and patient characteristics, suggesting that exposure to wildfire smoke pollutants may exacerbate acute respiratory distress.