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| New studies have shown that women who have a history of migraine preceded by visual disturbances can be at a 10 time higher risk for stroke when compared to women without migraine. |
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September 2007
Migraine has long been regarded as a risk factor for ischaemic stroke, but only few studies have addressed the potential reasons for an association between migraine and stroke.
In the "Stroke Prevention in Young Women Study" published in the American Heart Association’s journal "Stroke" a team headed by Dr Leah MacClellan reviewed data collected on 386 women (15–49 years) with first ischaemic stroke and 614 age- and ethnicity-matched controls in a population-based case-control study.
"Women with onset of probable migraine with visual symptoms (PMVA) in the previous 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 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 headache without aura, however, was not demonstrated to be a risk factor among the same study group.
"Young women with probable migraine with visual symptoms can reduce their risk of stroke by stopping smoking and finding alternatives to the use of oestrogen-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.
As alarming as the findings sound, the chance that a woman in the 15-to-49-age group will have an ischaemic 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 minimise 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 ischaemic 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."
The elevated risk of ischaemic stroke in women with migraine and visual aura was also discussed in the same issue of “Stroke” in an editorial written by Dr. Tobias Kurth, who has concentrated his research within the same area and found that migraine with aura alone was the most common risk factor for stroke in women under the age of 55.
His interpretation of the data collected by MacClellan and colleagues is that neither oral contraceptive use nor smoking alone substantially increased the odds ratio of ischaemic stroke among women with PMVA, but that the combination of both resulted in a 10-fold increased risk of stroke when compared with women without migraine who did not smoke and did not use oral contraceptives.
With regard to stroke subtypes, the proportion of lacunar infarction and stroke of undetermined origin was higher in women with PMVA but not atherosclerotic and cardioembolic strokes which differs from nonmigraine stroke patients in whom the latter two stroke subtypes are more frequent.
According to Dr. Kurth, very few of women with PMVA are at high risk of ischaemic stroke, but smoking increases this risk substantially, especially if the women also use oral contraceptives. Continued efforts are needed to communicate these scientific findings to patients.
Reference:
Stroke 2007; 38 (9): 2438–2445.
Stroke 2007; 38 (9): 2407–2408.
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