Wildfire Smoke Exposure Linked to Severe Headache Episodes, suggests study
Researchers have found in a new case-crossover study from Alberta and Ontario that acute exposure to wildfire-related PM2.5 was associated with increased emergency department visits for migraine or other primary headache syndromes (MOPHS). The association was stronger for wildfire-sourced PM₂.₅ than for non-wildfire PM₂.₅, suggesting that wildfire smoke may precede severe headache episodes requiring emergency care. Further research is needed to better understand the relationship between wildfire smoke exposure and severe headache outcomes.
The study was published in JAMA Network Open by Robert D. and colleagues. To assess the relationship between fine particulate matter with aerodynamic diameter of PM₂.₅ and ED visits for migraines and other primary headache syndromes (MOPHS), a case-crossover study employing conditional logistic regression was done. Data analysis was performed in the period between April and December 2025, where visits to the ED registered in the National Ambulatory Care Reporting System in the wildfire season (May 1 to October 31) of 2010 to 2023 in Alberta and Ontario, Canada, were analyzed.
Case and referent days were matched based on day of the week, month, year, and forward sortation area (first 3 digits of the postal code). Seven-day lag exposures were assessed. Mean wildfire-sourced PM₂.₅ exposure was determined based on Canadian Optimized Statistical Smoke Exposure Model, where smoke plumes were identified, along with the total PM₂.₅ exceeding a predefined threshold of mean + 1.5 SD of PM₂.₅ on non-smoke days.
Key findings:
- There were 997 701 visits for migraines (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision; canada code G43) and other primary headache syndromes (code G44) in emergency departments.
- Among the 997 701 emergency department visits for MOPHS identified during the study period, involving 622 753 patients (mean age 24.62 [16.82] years; 760 795 females or 76.3%), 86.2% were due to migraines and 13.8% to other headache syndromes.
- Wildfire PM2.5 was associated with 6.07% (95% confidence interval, 5.75%-6.39%) increase in emergency department visits.
- Effects appeared diminished in the least materially and socially deprived quintile (a smaller increase in MOPHS for Material and Social Deprivation Index quintile 1 compared to quintile 5 in both provinces combined).
- On the contrary, there was no significant association between the total PM2.5 concentration on non-WFDs and ED visits (0.21%; 95% confidence interval, −0.20% to 0.62%).
Acute exposure to wildfire-related PM2.5 was significantly related to an ED visit for MOPHS; acute exposure to wildfire-related PM2.5 demonstrated larger effects than nonwildfire-related PM2.5. Considering the increased severity and geographic spread of wildfires, public health policies need to emphasize clean air advice for the at-risk population, as well as setting up shelters with cooling and filtering systems, and early neurological interventions. Increased knowledge regarding smoke-related headaches will assist patients and emergency departments in dealing with acute neurological events due to wildfires.
Reference:
Dales R, Paul N, Cleland SE, et al. Wildfire-Sourced PM2.5 and Emergency Department Visits for Migraine and Other Primary Headache. JAMA Netw Open. 2026;9(7):e2625015. doi:10.1001/jamanetworkopen.2026.25015
