Weather and migraine: Can so many patients be wrong?

A migraine trigger is a factor which temporarily increases the probability that a migraine headache will occur, and many individuals with migraine blame certain weather conditions for initiating at least some of their migraine attacks (1,2). Some consider weather changes to be their most important headache trigger and even go so far as to refer to themselves as ‘human barometers’. A large, recent, clinic-based study of patient perceptions has indicated that 53% of migraine patients perceive that weather triggers their headaches at least occasionally, and 11% felt that weather triggered at least two-thirds of their headache attacks (2). The perception that weather can trigger headaches is not limited to patients with migraine; a substantial proportion of patients with tension-type headache also report weather as a headache trigger (3,4). While it might be argued that patient self-report of headache triggers from surveys based on memory of past events might be unreliable, data based on patient diaries where patients recorded the factor they felt was responsible for their headaches on a daily basis have given similar results (5). A population-based diary study in France performed in this manner indicated that 35% of migraine sufferers felt that weather had triggered at least some of their attacks. Of interest, similar to a clinic-based study (3), it was found that weather was reported as a headache trigger by a higher proportion of migraine patients as compared to patients with other headache types (35% vs 18%; P< 0.05) (5). On the other hand, in another clinic-based survey study of relatively severely affected headache patients, 45.5% of migraine patients listed weather changes as a headache trigger, and this was not different from patients with tension-type headache (48%) (6). In patients drawn from the general population, Rasmussen (4) found, perhaps surprisingly, that a higher proportion of people with tension-type headache reported weather as a headache trigger than did individuals with migraine. Clearly, when it comes to weather, many patients including both those with migraine and those with tension-type headache consider it to be a factor in triggering their attacks. Yet a very sophisticated recent study by Zebenholzer et al. (7) was unable to show any major connection between weather conditions and migraine occurrence. Although some association was shown between wind speed and day-to-day change of daily sunshine duration and migraine occurrence, none of these associations remained statistically significant after correcting for multiple testing by means of a Bonferroni correction (only P-values of <0.0018 were considered significant). The conclusion of the authors was that: ‘The influence of weather factors on migraine and headache is small and questionable’. Some previous studies which tried to identify weather factors as migraine triggers have also been negative (8,9). Others have shown at least some associations between certain weather conditions and migraine occurrence (10–15), but no consistent picture of which weather-related factors are important migraine triggers has emerged. Can so many migraine patients be wrong? Or is there another reason why research to date has been unable to measure the apparently robust association between weather and migraine attacks that so many of our patients tell us exists? Is the problem with the patients or with the research? Pertinent to this discussion is that a number of studies have found little correlation between whether patients think they are weather sensitive, and whether they actually are based on research results. Although Prince et al. (10) found that 50.6% of patients in their study were weather sensitive, there was no significant difference in the degree of weather sensitivity found