By Matt McMillen
WebMD Health News
Reviewed by Laura J. Martin, MD
Jan. 23, 2013 -- Worrying about what may trigger a migraine attack adds to the discomfort of many people with migraines. But according to a new study from Denmark, much of that worry may be unfounded.
The researchers studied the effect of light and exercise -- both commonly believed by patients to trigger migraine with aura -- and demonstrated that neither caused attacks in most of the people enrolled in the study.
"There are a lot of things about headache and migraine that are accepted as true but that remain untested," neurologist Peter Goadsby, MD, Dsc, says of triggers. "The results of this study may surprise some patients."
Goadsby, director of the University of California, San Francisco Headache Center, co-authored an editorial that accompanied the Danish study. In his clinical practice, he sees many patients whose quality of life suffers as a result of both their migraines and their efforts to avoid triggers that they believe will lead to attacks. In addition to light and exercise, other proposed triggers include stress, emotions, and certain foods.
But there's little evidence that any of these things really do trigger attacks, says Goadsby. He hopes that, in addition to the current study, there will be much more research on triggers.
"There are tens of millions of people with migraine," says Goadsby, "and all they have to go on are tales handed down about what triggers them."
Trying to Cause a Headache
To investigate the impact of light and exercise, researchers at the University of Copenhagen recruited 27 people who had migraine with aura, a condition in which headaches are preceded most often by other symptoms, such as blind spots and light flashes. Nausea, excessive yawning, and numbness are among the other possible aura symptoms. About 1 in 5 people with migraines has migraine with aura.
The study participants -- 17 women and 10 men whose average age was 40 -- all said that light or exercise, or a combination of the two, triggered their attacks. To test their claims, the researchers exposed each of the participants to their triggers.
In 30- to 40-minute sessions, one of three different types of stimulation was used to mimic the light that patients said triggered their migraines. The exercise portion of the study was also intense. Participants went running or pedaled on a stationary bicycle until they reached 80% of their maximum heart rate. Afterward, the researchers monitored the participants for three hours for symptoms.
Overall, only three of the 27 participants had an attack of migraine with aura: one after exercise alone and two following a combination of light and exercise. Another three participants had a migraine without aura. None of the participants had an attack after being exposed to light alone.
An Unnecessary Burden
The researchers conclude that exercise may be a real trigger of migraine with aura, at least among a small percentage of people, but they don't know exactly why. What clinicians do know is that too many people may be scared to exercise, which can have unhealthy consequences.
"I can't tell you how many of my patients say they won't exercise because they think they'll get headaches," says neurologist Jason Rosenberg, MD, director of the Johns Hopkins Headache Center in Baltimore. He reviewed the study for WebMD.
Rosenberg says that many people with migraines obsessively avoid certain foods, wear sunglasses indoors and outside, and engage in other burdensome, socially isolating behaviors.
"And once they decide what their triggers are," he says, "it is very difficult to change their minds."
The study authors, who did not respond to requests for comment, advise people to keep track of their headaches and whether avoiding certain triggers really makes a difference. If three months pass with no change in frequency, they write, it's likely safe to say that what they are avoiding is not a trigger after all.
While this study looked at only two potential triggers, it helps to "poke holes in urban legends in medicine," says Rosenberg.
"Avoiding exercise, sunlight exposure, and foods that are supposed to trigger migraines: None of these things have actually been tested," he says. "Studies like this will help me nudge patients in the right direction."
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