Women with recent onset of probable migraine with visual symptoms (within the prior year) were almost seven times more likely to have a stroke compared to women with no history of migraine," said Steven Kittner, M.D., M.P.H., senior author of the study and staff physician at Baltimore Veterans Affairs (VA) Medical Center. "Eight percent of stroke cases had onset of probable migraine with visual symptoms in the prior year compared to one percent of controls.
"Second, and probably the most important finding, women who had probable migraine with visual symptoms who also smoked and used oral contraceptives had seven times the risk of stroke than women who had probable migraine with visual symptoms alone."
Migraine and stroke share some common risk factors, including high blood pressure and patent foramen ovale (PFO); both have a hereditary basis. While a baby grows in the womb, he or she has a normal opening between the heart's left and right atria (upper chambers). If this opening doesn't close naturally soon after the birth, the hole is called PFO.
Furthermore, migraine has long been regarded as a risk factor for ischemic stroke (stroke caused by a blot clot blocking blood flow to the brain). Few prior studies have addressed the different potential reasons for an association between migraine and stroke.
Researchers analyzed stroke incidence among 386 women 15-to 49-years-old with a first ischemic stroke and 614 women of similar ages and ethnicities who had not had stroke. Based on their responses to a questionnaire, the women were classified into three categories: having no migraine; probable migraine without visual aura; or probable migraine with visual aura.
Kittner and colleagues also reported that, compared to women with no history of migraine, women with probable migraine with visual symptoms had a 1.5 greater risk of ischemic stroke.
"Young women with probable migraine with visual symptoms can reduce their risk of stroke by stopping smoking and finding alternatives to the use of estrogen-containing contraceptives," said Kittner, who is also professor of neurology at the University of Maryland School of Medicine and director of the Maryland Stroke Center in Baltimore, Md.
As alarming as the findings sound, the chance that a woman in the 15-to-44-age group will have an ischemic stroke is very low — one-to-two for every 10,000 people each year, Kittner said.
However, neurologists and other doctors should encourage their patients who have migraine with associated visual symptoms to minimize other stroke risk factors, he said.
"More work is also needed regarding whether patent foramen ovale mediates the association between probable migraine with visual symptoms and ischemic stroke," Kittner said. "We did not find evidence that this was the case, but had limited data to address this question.
"Other investigators should confirm our findings of an increased risk of stroke associated with recent onset of probable migraine with visual symptoms."