Neurology 2000 00, 54: 2, 302-7
OBJECTIVE: To determine the effects of chinook weather conditions on probability of migraine headache onset.
BACKGROUND: Many migraineurs believe weather to be a trigger factor for their headaches; however, there is little supportive evidence in the literature. Migraineurs in the southern part of the Canadian province of Alberta frequently report that chinooks, warm westerly winds specific to the region, trigger their headaches.
METHOD: Weather data from Environment Canada were used to designate each calendar day during the study period as a chinook, pre-chinook, or non-chinook day. Headache data were collected from 75 patient diaries from the University of Calgary Headache Research Clinic. Individual and multiple logistic regression models were used to determine if the weather conditions affected the probability of migraine onset. Results: The probability of migraine onset was increased on both pre-chinook days (odds ratio 1.24; 95% CI 1.08 to 1.42) and on days with chinook winds (1.19; 1.02 to 1.39) compared with non-chinook days. Analysis of chinook wind velocities revealed that for chinook days, the relative risk of migraine onset was increased only on high-wind chinook days (velocity > 38 km/h) (odds ratio 1.41; 95% CI 1.06 to 1.88). A subset of individuals was sensitive to high-wind chinook days, and another subset was only sensitive to pre-chinook days. Only two patients were sensitive to both weather conditions, and the majority of patients was not sensitive to either. Neither weather condition had a protective effect. Increasing age was associated with high-wind chinook sensitivity (p = 0.009) but not pre-chinook sensitivity (p = 0.389).
CONCLUSIONS: Both pre-chinook and high-wind chinook days increase the probability of migraine onset in a subset of migraineurs. Because few subjects were found to be sensitive to both weather types, the mechanisms for these weather effects may be independent. This is supported by the presence of an age interaction for high-wind chinook days but not for pre-chinooks day.