Impact of air pollution exposure on headache onset in migraine patients

Abstract text (incl. figure legends and references)

Question: Air pollution has a clear impact on people health"s increasing the risk of suffering from several diseases. We aimed to analyze whether if ambient air pollution triggers migraine attacks

Methods: This is a prospective longitudinal study. Headache daily status (headache free vs headache day) and GPS coordinates were collected using a custom-developed Smartphone App. Patients with migraine diagnosis seen in the Headache Clinic were recruited. Daily maximum 1-hour nitric oxide (NO), carbon monoxide (CO), sulfur dioxide (SO2), fine particulate matter (PM10) and ozone (O3) levels in the previous four days before headache onset were considered as possible explanatory variables for a binary outcome variable describing the potential daily headache status. A mixed-effects logistic regression model was performed. The model was adjusted by patient characteristics at baseline and meteorological parameters (daily mean temperature, relative humidity, accumulated precipitation, radiation and wind speed levels). It was validated using repeated 10-fold cross-validation.

Results: Sixty-six patients (80.3% women, mean age 48.7±9.2 years) contributed to 12,233 days of data, from which 1,668 days (13.6%) were headache days. Statistically significant differences in levels of daily maximum 1-hour NO (p=0.041), SO2 (p=0.010) and O3 (p=0.010) were found over the previous four days before headache onset. An increase in daily maximum 1-hour levels of NO2 of 35 µg/m³ (0.5·IQR, Interquartile Range) in the previous 48 hours was found to increase a 5.6% the probability of a headache onset (p=0.035). The presence of an attack on previous days was also associated with potential headache risk.

Conclusions: Headache onset in migraine patients might be influenced by greater air pollution on previous days. Air pollution, combined with other external and individual internal factors, has an impact on health status and might contribute to triggering migraine attacks.