Weather has long been considered a potential migraine trigger, but a new study links lightning, specifically, to their onset.
Based on headache logs and weather data for Ohio and Missouri, researchers found that people were 28% more likely to experience a migraine on days when lightning struck within 25 miles of their home.
"We're very surprised and very happy with the results in that this is the first study to link lightning to migraines," said Dr Vincent Martin, the study's senior author from the University of Cincinnati College of Medicine in Ohio.
Previous research has also found links between migraines and barometric pressure, temperatures, and humidity.
Most of the past studies looking at weather and migraines, however, relied on an individual's observations and did not always account for other, possibly unseen, local weather conditions, the researchers wrote online in Cephalalgia.
For the new study, they used information collected from three sensors that track lightning near Cincinnati, Ohio, and five sensors near St. Louis, Missouri.
They also used the headache diaries from two previous studies, in which 90 migraine sufferers in those areas recorded their headaches for three to six months.
After comparing the weather data with the headache journals, the researchers found that a lightning strike within 25 miles of a person's house was linked to a 31% increased risk of any kind of headache, and a 28% increased risk of the more severe migraine headache.
Dr Martin said that could mean an extra one to three migraines per month for an individual, but he added that it depends on the person and the weather.
As for how lightning might affect migraine occurrences, Dr Martin said it could be that the electromagnetic waves and ozone created by the lightning have something to do with it.
"The other theory is that when these thunderstorms roll in they can create more allergy spores in the environment," he said, which could create a problem for some people. But the researchers cannot say for certain that lightning causes migraines, even though they used a computer model to account for other meteorological changes that occur during a thunderstorm.
In an editorial, Dr Hayrunnisa Bolay of Gazi University in Ankara, Turkey, cautioned that the study had limitations, including its failure to account for participants' own individual risk factors."In brief, one can only conclude that weather conditions associated with lightning have the potential to induce headache in migraine patients," she wrote.
(Andrew M. Seaman, Reuters Health, January 2013)