Background: Many studies have indicated that weather can trigger headache. Here we propose a new methodological approach to assess the relationship between weather, ambient air pollution, and emergency department (ED) visits for this condition.
Objective: To examine the associations between ED visits for headache and selected meteorological and air pollution factors.
Design and methods: A hierarchical clusters design was used to study 10,497 ED visits for headache (ICD-9: 784) that occurred at a Montreal hospital between 1997 and 2002. The generalized linear mixed models technique was applied to create Poisson models for the clustered counts of visits for headache.
Results: Statistically significant positive associations were observed between the number of ED visits for headache and the atmospheric pressure for all and for female visits for 1-day and 2-day lagged exposures. The percentage increase in daily ED female visits was 4.1% (95% CI: 2.0, 6.2), 3.4% (95% CI: 1.4, 5.6), and 2.2% (95% CI: 1.4, 5.6) for current day, 1-day and 2-day lagged exposure to SO(2), respectively, for an increase of an interquartile range (IQR) of 2.4 ppb. The percentage increase was also statistically significant for current day and 1-day lagged exposure to NO(2) and CO for all and for female visits.
Conclusions: Presented findings provide support for the hypothesis that ED visits for headache are correlated to weather conditions and ambient air pollution - to atmospheric pressure and exposure to SO(2), NO(2), CO, and PM(2.5). An increase in levels of these factors is associated with an increase in the number of ED visits for headache.