Research Letter
Climate Change and Health
Excess Deaths Attributable to the Los Angeles Wildfires From January 5 to February 1, 2025
Eugenio Paglino, Rafeya V. Raquib, Andrew C. Stokes
JAMA Published Online: August 6, 2025
doi: 10.1001/jama.2025.10556
In January 2025, 2 major wildfires impacted Los Angeles County, California. Officials reported 30 direct fatalities,1but additional health impacts are likely.2
Excess mortality models have been applied to quantify the impacts of climate-related emergencies such as wildfires.3 Excess deaths from wildfires include deaths directly related to the wildfire, along with partially attributable deaths (eg, from lung or heart conditions exacerbated by smoke or stress) and indirect deaths (eg, disruptions to health systems, mental health impacts).4,5
This study estimated excess deaths attributable to the Los Angeles wildfires using an interrupted time series design.
Methods
This cross-sectional analysis was determined to be exempt from review and informed consent requirements by the Boston University Institutional Review Board, as it did not involve human participants. The study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
We extracted weekly all-cause death counts by county of residence for Los Angeles County. We adopted an interrupted time series design and used a negative-binomial generalized additive model to estimate expected deaths from January 5 to February 1, 2025 (weeks 2 through 5 of 2025). We fit our model on data from 2018, 2019, and 2024, excluding 2020 to 2023 due to the COVID-19 pandemic. We calculated excess deaths as the difference between observed and expected deaths, and population-attributable fractions as excess deaths divided by observed deaths. We computed percentile-based 95% confidence intervals and the probability of positive excess mortality. Sensitivity checks are detailed in the eMethods in Supplement 1.
Results
In Los Angeles County, weekly deaths consistently exceeded expected deaths during the period from January 5 to February 1, 2025 (Table 1). In total, 6371 deaths were observed compared with 5931 (95% CI, 5627 to 6240) expected deaths (Table 1). This indicates that 6.9% (95% CI, 2.1% to 11.7%) of the observed deaths or 440 (95% CI, 131 to 744) deaths in Los Angeles County were excess deaths.
Table 1. Estimation of Weekly and Total Excess Deaths Attributable to the California Wildfires in Los Angeles County From January 5 to February 1, 2025a
| Calendar week | Observed deaths, No. | Expected deaths, No. (95% CI) | Excess deaths, No. (95% CI) | Pr(Excess >0) | PAF, % (95% CI) |
|---|---|---|---|---|---|
| 2 | 1570 | 1484 (1357 to 1618) | 86 (−48 to 213) | 0.91 | 6.0 (−3.0 to 15.7) |
| 3 | 1592 | 1492 (1360 to 1616) | 100 (−24 to 232) | 0.94 | 6.9 (−1.5 to 17.1) |
| 4 | 1570 | 1484 (1355 to 1621) | 86 (−51 to 215) | 0.90 | 6.0 (−3.1 to 15.9) |
| 5 | 1639 | 1472 (1342 to 1597) | 167 (42 to 297) | >0.99 | 11.6 (2.6 to 22.1) |
| Total | 6371 | 5931 (5627 to 6240) | 440 (131 to 744) | >0.99 | 6.9 (2.1 to 11.7) |
Excluding selected causes of death had minimal impact on the results (Table 2). Using an alternative, controlled interrupted time series design led to slightly more conservative estimates, while including data for 2023 in the model raised the number of excess deaths. Across all sensitivity analyses for weeks 2 through 5, the probability of positive excess exceeded 0.98 (Table 2). Including 4 additional weeks (weeks 6 through 9) lowered excess deaths to 332 (95% CI, −134 to 812), with a 0.92 probability of positive excess. A placebo test performed by removing the last 5 weeks of 2024 from the training data and comparing observed and expected deaths for this period showed no significant excess mortality (Table 2).
Table 2. Results From Sensitivity Analysesa
| Specification | Observed deaths, No. | Expected deaths, No. (95% CI) | Excess deaths, No. (95% CI) | Pr(Excess >0) | PAF, % (95% CI) |
|---|---|---|---|---|---|
| Primary analysis | |||||
| All causes (2020-2023 excluded) | 6371 | 5931 (5627 to 6240) | 440 (131 to 744) | >0.99 | 6.9 (2.1 to 11.7) |
| Sensitivity analyses | |||||
| Removing influenza and pneumonia (2020-2023 excluded) | 5999 | 5612 (5344 to 5861) | 387 (138 to 655) | >0.99 | 6.5 (2.3 to 10.9) |
| Removing all respiratory diseases (2020-2023 excluded) | 5693 | 5302 (5063 to 5557) | 391 (136 to 630) | >0.99 | 6.9 (2.4 to 11.1) |
| Removing all external deaths (2020-2023 excluded) | 5965 | 5546 (5231 to 5875) | 419 (90 to 734) | >0.99 | 7.0 (1.5 to 12.3) |
| All causes CITS design (2020-2023 excluded) | 6371 | 422 (9 to 807) | 0.98 | 6.6 (0.1 to 12.7) | |
| All causes (2020-2022 excluded) | 6371 | 5815 (5547 to 6078) | 556 (293 to 824) | >0.99 | 8.7 (4.6 to 12.9) |
| All causes, weeks 2-9 (2020-2023 excluded) | 12 009 | 11 677 (11 197 to 12 143) | 332 (−134 to 812) | 0.92 | 2.8 (−1.1 to 6.8) |
| All causes placebo (2020-2023 excluded) | 6966 | 7134 (6809 to 7481) | −168 (−515 to 157) | 0.16 | −2.4 (−7.4 to 2.3) |
Discussion
While there were only 30 direct fatalities from the Los Angeles wildfires,1 this study estimates that 440 deaths from January 5 to February 1, 2025, were attributable to the wildfires. These additional deaths likely reflect a combination of factors, including increased exposure to poor air quality and health care delays and interruptions.3,5 Results from a sensitivity analysis including data up to March 1, 2025, are compatible with a selection effect, but are likely affected by incomplete reporting of deaths.
The findings from this study underscore the need to complement direct fatalities estimates with alternative methods to quantify the additional mortality burden of wildfires and of climate-related emergencies more broadly. They also highlight the need for improved mortality surveillance during and after wildfire emergencies.6
This study has limitations. First, the data are provisional and may be revised to include additional deaths. Second, additional excess deaths may have occurred beyond the period of the current study. Third, although numerous robustness tests were performed, it is possible that the estimates were affected by residual or unmeasured confounding. Future research should investigate the longer-term impacts of the Los Angeles wildfires as additional data become available and assess the specific causes of death contributing to excess wildfire-related mortality.
