When the weather forecast foretells a coming storm, some get out not only their umbrella and wellies but also the Advil. The weather has been blamed for ailments from arthritis flare-ups to coughs, but is it culpable when it comes to headaches?
Studies looking into the headache-weather connection tend to fall into one of two types: observational studies, where participants self-report their headaches, or retrospective looks at hospital records. Both approaches have their strengths, weaknesses, and biases, but together can they tell us anything about how the weather affects headaches?
With the first type of study, the results tend to show associations between weather and cephalalgia (the formal name for headaches), but not tremendously strong ones. For example, Prince et al. reviewed calendar data for 77 subjects with migraine and found 50.6% were sensitive to at least one weather factor. Zebenholzer et al. meanwhile reviewed 90-day calendar data in winter from 238 subjects with migraine and found no statistically significant association. A 2018 study used daily reports on health symptoms from 4548 individuals over one month in Japan and correlated them to local weather data. Despite finding a statistically significant relation between weather and various physical symptoms, all the effect sizes were so small that the authors conclude, "in large, weather effects on human’s mood appear insignificant".
As Maini and Schuster write, "Multiple studies have been performed with inconsistent results regarding the directionality of the association between atmospheric pressure changes and triggering of primary headache disorders, chiefly headaches."
A lot of smartphone studies have looked at this query. A web and smartphone study in Germany found an increased rate of migraine reports on days of significant weather changes, especially a 5 °C temperature increase. A new smartphone study was published in 2023 in which researchers examined 4375 users with 336,951 hourly headache events and weather data from December 2020 to November 2021. They conclude, "low barometric pressure, barometric pressure changes, higher humidity, and rainfall were significantly associated with headache occurrence."
The hospital studies, meanwhile, show similar levels of disagreement. Mukamal et al. looked at 7054 patients seen for headaches in the Emergency Department and reviewed meteorological data for the days prior to their visit. They found that visits for headaches or migraine were more frequent during days of higher mean temperatures in the 24 h before the visit. Yilmaz et al. reviewed 3491 patients admitted to the Emergency Department for migraine and found significant associations with high temperatures and low humidity, whereas Villeneuve et al., on the other hand, found no significant relationship between 4039 ED visits for migraine and any weather condition.
Despite a plethora of attempts to investigate this question, the matter still needs to be definitively solved. What's the problem here?
A big part of the confusion is due to the many individualized factors that can cause, worsen and attenuate a headache. Certain smells, a lack of caffeine, being overheated, specific sounds, too much caffeine, not eating, cold ears, muscle tension, the list of potential headache triggers is long. All of these factors complicate understanding how weather affects headaches. How do we know if someone's reported headache was due to a weather change, or their hormones, lack of sleep or new hairstyle?
Even within the very concept of "weather" causing headaches, what do we mean? Pressure? Temperature? Precipitation? Wind? Humidity? What about air-borne contaminants like bacteria, dust, or sand?
The evidence seems to have adequately correlated headaches to changes in the weather, even potentially with periods of low barometric pressure such as precedes stormy weather, but the question of mechanism, of how weather can make our heads ache remains to be answered.
Scientists have some theories, mostly involving sinus pressure or the sympathetic nervous system, but nothing definitive. Even if we know the mechanism, there's nothing we can do to stop weather-induced headaches. But that isn't likely to stop the researchers from investigating this topic. I'll keep an eye out for any new publications about it.