Friday January 25 2013
Environmental migraine triggers include changes in temperature
Lightning could cause headaches and migraines, The Daily Telegraph reports, with the Daily Mail adding that the number of migraines rises by a third during thunder and lightning storms.
The idea that environmental factors can trigger the symptoms of migraine is nothing new. Previously reported triggers include bright lights, changes in temperature and a stuffy or smoky environment.
This study looked at a sample of 90 migraine sufferers who were taking part in two separate US trials investigating different treatments for migraine. These people kept headache diaries, and the researchers looked at how their reporting of headaches corresponded to weather reports in their local areas. They found that overall, participants were around a third more likely to report a headache or migraine on a day when there was lightning compared to a day when there was no lightning.
However, the findings do not prove that lightning was the direct cause of the headaches of people in this study.
Also, the small number of people taking part in these two select US trials of migraine treatments may not be representative of all people who suffer from migraines.
As the researchers responsibly conclude, until replicated by further study, their results ‘should be interpreted cautiously’.
Even if you choose to take the media’s reporting of this study at face value, there does not seem to be much practical advice you can take from it, unless you have the means and opportunity to move to somewhere where lightning storms are rare.
Where did the story come from?
The study was carried out by researchers from the University of Cincinnati College of Medicine, Ohio, and other centres in the US and was funded by the drug company GlaxoSmithKline (as no drug treatments for migraine or headaches were discussed in this study there does not appear to be any potential conflict of interests).
The study was published in the peer-reviewed journal Cephalagia: An International Journal of Headache.
The media’s reporting is generally representative of the findings of the study, but doesn’t mention its limitations – most importantly that this small study does not prove that lightning was the cause of these headaches.
What kind of research was this?
This was an observational study that used data obtained from two previous headache trials. The current analysis was trying to examine whether lightning could have a role in provoking migraine. They wanted to see whether, in people who suffer from migraine, their headaches were more common on days where there was lightning, compared to days where there wasn’t.
Migraine is a severe headache that is often accompanied by nausea and vomiting as well as an aversion to light and sound. Migraine with aura is when the headache is preceded by neurological symptoms, most often visual symptoms such as seeing flashing lights. Migraine may be triggered by different things in different people, such as something you eat or drink, stress, exercise, menstruation in women, or other factors.
In some cases, possible environmental triggers have been reported, such as high temperature and humidity, as well as thunderstorms.
The difficulty is in proving that the weather events observed were the direct cause of migraine in people in this study; and even if lightning may contribute to triggering a migraine in some, it may not do so in all migraine sufferers.
What did the research involve?
Two previous trials had been conducted in Cincinnati, Ohio, and St. Louis, Missouri – two states in the American mid-west where thunder and lightning storms tend to be more common than in the UK.
The Cincinnati trial investigated the effect of medical oophorectomy (using a hormone medication to stop the ovaries functioning) on migraine in female sufferers.
The St. Louis trial investigated the effect of patient education (for example; which triggers to avoid or which medications to use to stop the headache). Participants in each of the trials had completed a daily headache diary for three to six months, including documenting the presence or absence of headache, how severe the headache was (rated on a ten-point scale), and the associated symptoms such as nausea, vomiting, and aversion to light and noise.
Weather data was collected from a company that had data on the location, current, and polarity (whether the electricity released during the strike was positively or negatively charged) of all cloud-to-ground lightning strikes around the Cincinnati and St. Louis areas during the study periods. They also collected hourly data on surface weather variations such as changes in temperature, humidity, wind speed and direction, air pressure and precipitation. They also looked at measures of the stability of the weather pattern.
For each participant, the nearest post office in their home zip (post) code area was used as a reference point. The distance of all lightning strikes from that location was assessed. The researchers used statistical methods to examine the odds of a person reporting a headache on days when there was lightning in their area (within 25 miles of their zip code) compared to no lightning.
What were the basic results?
The study included 90 participants – 23 from the Cincinnati trial and 67 from the St Louis trial. The average age of all 90 participants was 44 and 91% were female. Participants suffered from non-migraine headaches an average of 11.7 days per month, and migraines on 6.6 days per month. Thunderstorms were similarly common in the Cincinnati and St Louis regions, and occurred, on average, 21.5% of days during the study periods (266 days).
Compared to days without lightning, on a day when there was lightning, people had:
- a 31% increased odds of reporting any headache (odds ratio [OR] 1.31, 95% confidence interval [CI] 1.07 to 1.66)
- 28% increased odds of reporting a migraine (OR 1.28, 95% CI 1.02 to 1.61)
Adjusting the analyses for other weather variables, such as stability of the weather and the season, reduced the strength of the association with headache, but did not remove statistical significance.
Adjusting for some other weather factors, such as season, did make the link between lightning and migraine non-significant.
How did the researchers interpret the results?
The researchers conclude that lightning represents a trigger for headaches and migraine in sufferers, independently of other associated weather factors.
The researchers say they do not know the cause – whether lightning directly triggers headaches through electromagnetic waves or whether it could be an indirect effect through other mechanisms, such as the production of bioaerosols (such as ozone) or increases in the circulation of fungal spores. They say that their results ‘should be interpreted cautiously until replicated in a second dataset’.
This study finds that the people in these two trials were around a third more likely to report a headache or migraine on a day when there was lightning.
Migraines can be triggered by different things in different people, including food, drink, stress, exercise or other activities. Some people do report that environmental or weather factors can have an effect on their headaches. Therefore, lightning as a possible trigger for headache or migraine in some sufferers is certainly plausible. However, the findings do not prove that lightning is the direct cause of the headaches of people in this study.
Importantly, this is a very small sample of only 90 people taking part in two separate trials investigating different treatments for migraine. This small group of people may not be representative of all people who experience migraines, particularly as they are likely to have very specific characteristics that have caused them to be enrolled in the trials to start with. For example, the Cincinnati trial was investigating the effect of hormone treatment to stop the ovaries from functioning in women aged 18-45. To have been enrolled in a trial of such a radical treatment suggests that for these women, menstruation was strongly believed to be linked to their migraines.
Even for this small sample, linking the weather features in their area of residence to their reporting of headaches or migraine on that day does not prove that the weather feature was the direct cause.
The researchers also had no information about where each individual was on the day of the lightning, and therefore whether they really were exposed to it or not.
Not all people kept their headache diaries for an entire year, so some of the differences seen could be due to different people being assessed during seasons when lightning was more likely than when lightning was less likely.
Overall, as the researchers responsibly conclude, until replicated by further study, their results ‘should be interpreted cautiously’.
Learning to recognise potential migraine triggers – such as stress, alcohol, or hunger – and then taking steps to avoid them is an important part of living with the condition.
However – if lightning does trigger migraines in some people – there does not seem to be much people could do to avoid exposure to it.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.