Air Pollution and Emergency Department Visits for Headache and Migraine

Background: Associations between ambient air pollution and emergency department (ED) visits for headache and migraine were examined in a multi-city study during the period of April 2004 to December 2011 in nine cities across Ontario, Canada. Objectives: Evaluate potential positive associations between air pollution and ED visits for headache. Materials and Methods: Data on ED visits for headache were retrieved from the national ambulatory care reporting system in Canada. Case-crossover design was used for this study for three diagnosis categories: migraine, headache-OS (other specified, OS) and headache-NOS (not otherwise specified, NOS). A time-stratified case-crossover technique was applied to investgate the associa- tions of ED visits for headache with ambient air pollution. Odds ratios (ORs) and their corresponding 95% confidence intervals for ED visits associated with increased levels of air pollutants were calculated by applying conditional logistic regression. Results: Among females, statistically significant positive results were observed for one unit increase in inter-quartile range (IQR) of NO2 (IQR = 9 ppb) for lag 0 days: OR = 1.015 (1.000, 1.030) for migraine and for NOS: for NO2 for lags 0 to 2, where the highest result was for lag 0: OR = 1.015 (1.005, 1.026), for SO2 (IQR = 2.5 ppb) for lag 2: OR = 1.012 (1.002, 1.021) and for PM2.5 for lags 1 and 2, OR = 1.011 (1.002, 1.021) and OR = 1.010 (1.000, 1.020) respectively among females. No significant statistically significant results were observed among males. Conclusions: Our findings support a number of statistically significant positive associations between air pollutants and the num- ber of ED visits for headache and migraine.