Migraines May Increase Stroke Risk
But Birth Control Pills, Smoking Increase Risk Much More
Dec. 14, 2004 -- Migraine sufferers have double the risk of strokes, a new study shows. And those who also take birth control pills have about eight times the risk, say researchers.
However, people should not get too upset - unless they smoke, the researchers say.
"I have been receiving emails from people who are concerned about this. But they should definitely not get alarmed," says Mayhar Etminan, PhD, an epidemiologist at Royal Victoria Hospital and McGill University in Montreal. His study appears in this week's issue of the British Medical Journal.
"To put the results into perspective, for people under age 45, the risk of stroke is extremely low," Etminan tells WebMD. "There are other risk factors for stroke that further increase the risk, like smoking or taking birth control pills. But even when you factor those in, and double that risk, it's still low."
Some studies have found a nearly similar pattern -- that for women, migraines with aura (visual changes that precede migraine) increase the risk of transient ischemic stroke. These strokes are caused by blood clots in arteries to the brain. One study published two years ago found up to 10 times the risk for these women.
Priscilla Potter, MD, a neurologist and migraine specialist at the University of Miami School of Medicine, takes issue with these claims. "It is an overestimation of the risk," she tells WebMD. "What really increases stroke risk is clot formation. You get clots with birth control pills, with migraine headaches, with smoking. If you have all those, your risk of stroke can actually be pretty high."
Migraines and Stroke Risk
In his report, Etminan analyzed 14 of these smaller studies to get the bigger picture. He found higher stroke risk among all migraine sufferers.
- Men and women with migraines had twice the risk -- whether or not they had aura -- as non-sufferers.
- Women under age 45 who were taking birth control pills had a nearly ninefold increased risk. However, this finding is at odds with other studies, so more research is needed, says Etminan.
The study helps reveal the mechanism that connects migraines and stroke, Etminan says. It's believed that reduced blood flow to the brain, as usually happens during migraines, increases the risk of strokes. Also, some migraine sufferers' blood may have a higher tendency to clot. "But we really don't know why," says Etminan. "More research has to be done."
"We know from other studies that migraine with aura is an increased risk of stroke," Potter tells WebMD. "Birth control pills increase that risk, but not as much as these researchers say. I personally advise patients to not take birth control pills. But if they do, take aspirin since aspirin inhibits clot formation. Also, they should not smoke."