Lightning Triggers Headaches in Migraineurs
Lightning is associated with an increased risk for headache in patients with migraine, a new study shows.
Researchers report that on days with lightning compared with nonlightning days, the overall frequency of headache in their study was increased by 31% and that of migraine by 28%. In addition, the study showed that new-onset headache and migraine on lightning days increased by 24% and 23%, respectively.
"Therefore, lightning appears to be associated both with the presence of headache on a given day as well as the transition from a headache-free day to a headache day," the authors, led by Geoffrey V. Martin, BS, Department of Internal Medicine, University of Cincinnati College of Medicine, Ohio, write.
The observational cohort study was published online January 24 in Cephalalgia, a journal of the International Headache Society.
Headache Data
Researchers used headache data from 2 prior trials: a randomized, double-blind, placebo-controlled trial from Cincinnati, Ohio, that investigated the effects of medical oophorectomy on the frequency and severity of migraine headaches in premenopausal migraineurs and a trial from St. Louis, Missouri, comparing the frequency and disability of headaches in patients with migraine randomly assigned to patient education or to usual care.
The study included 90 participants (23 from Cincinnati and 67 from St. Louis). The cohort was mostly women (91%), with a mean age of 43.6 years.
Study patients recorded daily headache activity in a diary. Each patient had at least 90 days of data collection. The mean headache and migraine frequencies were 11.7 and 6.6 days per month, respectively.
For this study, the migraine outcome measure required the presence of moderate to severe headaches along with migraine-associated symptoms. The less stringent headache outcome measure included all headaches regardless of their characteristics.
"We believe that both outcome measures likely reflected migraine headaches as all our patients were migraineurs, and even the headache days that did not fulfill migraine criteria may have simply represented a migraine attack that was early or late in its course and therefore lacked migraine characteristics," the authors write. They add that early treatment with an abortive medication may have prevented the development of migraine symptoms with some attacks.
Lightning Data
Weather data included the location, current, and polarity of all cloud-to-ground lightning strikes around the Cincinnati and St. Louis areas during the study periods. Surface weather variables included temperature, relative humidity, wind speed, wind direction, barometric pressure, and precipitation. Insolation, a measure of solar radiation, was also measured hourly.
As well, the researchers used data from 2 weather instability indices: convection available potential energy (CAPE) and lifted index . These are used to predict unstable weather patterns, such as severe thunderstorms, hail, and tornados.
A lightning day was defined as 1 or more lightning strike occurring within 25 miles of a patient's postal zip code, an area in which patients were deemed most likely to reside throughout a day.
Using quantitative lightning data strengthened the study because it allowed the precise determination of the location and timing of lightning strikes. "This allowed us to accurately identify which days were truly lightning days for each individual patient in the study," the authors write.
The researchers found that the unadjusted odds ratios (ORs) for the frequency of headache and migraine on lightning days compared with nonlightning days were 1.31 (95% confidence limits [CL], 1.07 -1.66) and 1.28 (95% CL, 1.02 - 1.61), respectively.
After adjustment for the previous 2 days of headache or migraine activity, the ORs of headache and migraine on lightning days were 1.24 and 1.23. This lag analysis provided evidence for the frequency of new-onset headache and migraine.
Importantly, the study showed that the weather instability indices were associated with an increased frequency of headache and migraine. Controlling for CAPE did not significantly change the ORs, and after adjustment for lifted index, the OR of lightning was only reduced to 1.18 for headache and to 1.20 for migraine.
"An advantage of using instability indices as predictors of headaches as opposed to the presence of lightning is that these variables can be forecast days in advance," said the authors. "If validated in future studies these indices could be used to predict headache and/or migraine in weather-sensitive migraineurs."
It's not clear how lightning or its associated meteorologic factors might trigger headache. However, according to the authors, possible mechanisms could relate to sferics, the low-frequency electromagnetic waves that emanate from electrical storms; positive air ionization from electrical storms; or the production of irritable aerosols, such as nitrogen oxides and ozone, and allergenic fungal spores.
A limitation of the study was that each patient did not record headache data for an entire 12 months. As well, the results may not apply to persons with relatively infrequent headaches or to those living in other regions of the country.
Possible Mechanisms
In an accompanying editorial, Hayrunnisa Bolay, MD, PhD, Gazi University, Department of Neurology and Neuropsychiatry Centre, Turkey, outlined other limitations, including the facts that most patients in the study were women and that the study did not evaluate other trigger factors along with weather. As well, Dr. Bolay stressed that the study was not corrected for multiple comparisons because lightning and weather variables are highly intercorrelated.
In her editorial, Dr. Bolay also outlined the events that occur during lightning. Colliding particles of rain, ice crystals, or snow and their strong movements increase the electrical imbalance and negative charge of the lowermost part of storm clouds. The electrical discharge results from imbalance between negatively charged storm clouds and positively charged objects on the ground.
"Lightning produces enormous power and heat, and each strike can contain several hundred million volts of electricity," Dr. Bolay writes. "Such an energy outbreak induces rapid change in the chemical composition of the atmosphere."
One of the important components of complex atmospheric weather is dust, the presence of which increases the probability of cloud-to-ground lightning flashes, said Dr. Bolay.
What's required, she concluded, is a detailed prospective clinical study that explores "every single item including dust, microorganism, and bacterial and fungal spores, charged ions, sferics, NOx [nitrogen oxides], nanoparticles, bio-available iron content in the weather besides other well-known parameters such as pressure, temperature, humidity, rain, and lightning."
The study was not supported by external funding. Dr. Martin and Dr. Bolay have disclosed no relevant financial relationships. For conflict of interest information on other authors, see original article.
Cephalalgia. Published online January 24, 2013. Abstract Editorial
Medscape Medical News © 2013 WebMD
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