Acute Environmental Triggers and Intermediate-Term Modulators of Emergency Migraine-Related Health Care Encounters

Migraine activity is shaped not only by the biological vulnerability but also by environmental factors that may influence susceptibility and contribute to fluctuations in migraine occurrence, although the evidence remains inconsistent. We aimed to evaluate the intermediate-term and short-term effects of environmental exposures on migraine activity and to examine a conceptual layered model comprising biological vulnerability, intermediate-term environmental modulators, and acute triggers.

We conducted a population-based case-crossover study among patients with migraine identified from the Negev Migraine Cohort (2000-2023), using electronic medical records from Clalit Health Services and Soroka University Medical Center. Eligible participants were adult patients (≥18 years) residing in Be'er Sheva, Israel, with migraine diagnoses or triptan prescriptions. Daily exposure to air pollutants and meteorologic conditions were obtained from fixed monitoring stations. Outcomes were emergency migraine-related encounters as a marker of triggered events and quarterly triptan use as a marker for disease activity. Intermediate-term modulators were defined as weekly climatic conditions hypothesized to modify the short-term effects of daily exposures. Associations were evaluated using conditional logistic and Poisson regression.

The analysis included 7,032 adult patients with migraine residing in Be'er Sheva. Short-term exposure to nitrogen dioxide (NO₂) (odds ratio [OR] 1.41; 95% CI 1.13-1.77) and solar radiation (OR 1.23; 95% CI 1.07-1.42) was associated with an increased risk of emergency migraine-related encounters. Cumulative exposure to NO₂ was associated with a higher triptan use (incidence rate ratio [IRR] 1.10; 95% CI 1.00-1.21), as was cumulative particulate matter ≤2.5 µm (PM_2.5) exposure during the preceding quarter (IRR 1.09; 95% CI 1.00-1.19). Weekly climatic conditions modified short-term effects: high temperatures and low humidity during summer amplified NO₂-related risk (OR 2.18; 95% CI 1.06-3.30), whereas cold and humid winter weeks intensified the effect of PM_2.5 (OR 3.78; 95% CI 1.74-5.82).

Short-term and cumulative exposure to ambient air pollution and climatic factors were associated with increased migraine activity. Although these findings support a layered model of environmental modulation of migraine activity, their generalizability is limited by the use of emergency health care encounters as a proxy outcome, underscoring the need for further research using complementary measures.