Lightning has a unique effect on headache that is unrelated to other meteorologic factors, according to researchers.
WASHINGTON, DC—The frequency of headache and migraine is increased by 31% and 28%, respectively, among patients with migraine on days when lightning occurs compared to days without lightning, according to research presented at the 53rd Annual Scientific Meeting of the American Headache Society.
“To our knowledge, this is the first study to report that lightning represents a significant trigger for the development of headache in migraineurs,” reported Vincent Martin, MD, Clinical Professor in the Department of Internal Medicine, University of Cincinnati College of Medicine, and colleagues. “After adjusting for the meteorologic factors associated with thunderstorms, there still remains an increased frequency of headache on lightning days. This suggests that lightning has a unique effect on headache that cannot be explained by other meteorologic factors.”
Weather and Headache
The study included 90 patients from two datasets (91% female; mean age, 43) who had recorded headache diaries for at least 90 days and up to six months. All patients were living in Cincinnati or St. Louis and had had at least one migraine per month, according to the International Headache Society Diagnostic Criteria for Migraine. Overall, patients had an average of 11.7 headache days per month, and 6.6 migraine days per month.
Dr. Martin’s group obtained information regarding the location, amperage, and polarity of lightning strikes that occurred in the area of study participants. Data were also gathered regarding nonlightning-related weather variables, including temperature, barometric pressure, insolation (eg, a measure of solar radiation), and weather instability factors, which are indices used by meteorologists to predict when conditions are favorable for stormy weather. Weather values were assigned to each participant based on the weather value that was closest to the participant’s home zip code.
The primary outcome measure was presence of headache, and the secondary outcome measure was presence of migraine. The investigators defined migraine days as those with a peak headache severity score of 4 or greater on a scale of 10, along with the presence of either nausea or vomiting or both photophonia and phonophonia. Lightning days were defined as days when one or more lightning strikes occurred within 25 miles of a patient’s home zip code.
Generalized estimating equations were used to determine the odds ratio of headache and migraine on lightning days versus nonlightning days. The study authors also devised a propensity model to predict the probability of the presence of lightning using a logistic regression with surface weather factors as predictors. The propensity score was later added as a separate variable in their logistic models to determine if lightning had a unique effect on headache after controlling for the common meteorologic factors associated with a lightning day.
A Trigger for Headache
Participants recorded a total of 11,193 diary days, and headache occurred on 36% of these days. About 53% of the headache days were likely migraine, according to the researchers. Lightning occurred on 13% of the total days.
Dr. Martin and colleagues found that the group odds ratio of headache on lightning days was 1.31, and the odds ratio for migraine on lightning days was 1.28. After adjusting for propensity and instability factors, the researchers found that the effect of lightning on headache and migraine was lessened, but the results remained statistically significant. “When days were matched by similar propensity scores, headache was increased 3% on lightning days compared with nonlightning days, and migraine was increased 1%,” the authors stated. “The probability of headache on lightning days was further increased when lightning strikes had a more negative average current and when they were at least 15 miles from an individual’s home zip code.
“The weather instability indices that predict thunderstorms may be able to forecast days with an increased risk for lightning-associated headaches,” Dr. Martin and colleagues concluded.
—Colby Stong