Association between wildfire smoke exposure and pediatric emergency department visits for headache

The purpose of this study was to determine whether short-term exposure to wildfire smoke is associated with emergency department visits for headache in children and adolescents.

Wildfires are becoming increasingly common and are associated with numerous adverse health outcomes. However, we currently do not know how wildfire smoke exposure affects children and adolescents with primary headache disorders. Headache disorders in youth are a major contributor to frequently missed school days and youth with headache disorders have high medical care utilization and total healthcare costs. Therefore, understanding factors that may contribute to headache exacerbations and potential increases in healthcare utilization is of particular interest.

This was a time-stratified case-crossover study linking daily health data from the California Department of Health Care Access and Information to daily ZIP code-level wildfire PM_2.5 concentrations between 2006 and 2019. We included all visits for headache to emergency departments in California among youth 5-19 years old during the study period. The primary exposure was the ZIP code-level daily wildfire-specific PM_2.5 concentration, modeled as a continuous and binary (wildfire-specific PM_2.5 ≥15 μg/m³) variable. The primary outcome was an emergency department visit for headache. We identified relevant encounters according to the International Classification of Diseases, 9th/10th revision codes assigned in the first diagnostic position. To capture a potential delayed impact, we estimated odds ratios for the association for days 0 to 6 between the exposure and outcome.

We identified 206,230 unique emergency department encounters for primary headache disorders. Most visits were in female patients (61.4%) 15-19 years old (58.5%) who identified as Hispanic (48.8%) and lived in a very low-opportunity (37.7%) or low-opportunity (21.6%) neighborhood. The adjusted odds of an emergency department visit incrementally decreased per unit increase in wildfire-specific PM_2.5 concentrations from days 0 to 6 after wildfire smoke exposure (same-day adjusted odds ratio [aOR], 1.00; 95% confidence interval [CI], 0.998-1.001; day +6 aOR, 0.995; 95% CI, 0.993-0.997). Using a binary exposure, the adjusted odds of an emergency department visit incrementally decreased from days 0 to 6 after a wildfire smoke day (same day aOR, 0.99; 95% CI, 0.92-1.08; day +6 aOR, 0.84; 95% CI, 0.78-0.92).

Children are less likely to seek care in the emergency department for primary headache in the days following exposure to wildfire smoke, suggesting that healthcare utilization changes during wildfires. Clinicians should ensure youth with headache disorders who experience worsening symptoms associated with air pollution are equipped with strategies to manage their headache disorder at home during days with wildfire smoke, including effective at-home acute headache medications.