Researchers have affirmed that migraine headaches are associated with more than twofold higher chances of ischemic stroke. Ischemic stroke is the most common kind of stroke and occurs when blood supply to the brain is suddenly cut off by the buildup of plaque or a blood clot.

The researchers from Johns Hopkins pooled results from studies involving 622,381 men and women. Study participants were between the ages 18 and 70, and none had suffered a stroke prior to enrollment.

The risk of stroke for those with migraines is 2.3 times more than those without, and for those who experience aura, the sighting of flashing lights, zigzag lines and blurred side vision along with migraines, the risk of so-called ischemic stroke is 2.5 times higher, and in women, 2.9 times as high.

Senior study investigator Saman Nazarian says the team's latest analysis, believed to be the largest study of its kind on the topic, reinforces the relationship between migraine and stroke while correcting some discrepancies in previous analyses. For examples, a smaller combination study in 2005 by researchers in Montreal showed a bare doubling of risk, yet mixed together different mathematical measures of risk, while the Hopkins study kept them separate, pooling together only like measures. As well, another half dozen recent and smaller studies from Harvard University yielded mixed results, some showing a link between migraines and ischemic stroke, while one did not show a tie-in.

Nazarian says that while nearly 1,800 articles have been written about the relationship between migraine and ischemic stroke, the Hopkins review was more selective, combining only studies with similar designs and similar groups of people, and more comprehensive, including analysis of unpublished data.

"Identifying people at highest risk is crucial to preventing disabling strokes," says Nazarian. "Based on this data, physicians should consider addressing stroke risk factors in patients with a history or signs of light flashes and blurry vision associated with severe headaches."

Prevention and treatment options for migraine range from smoking cessation to changes in diet. Stopping use of oral contraceptives or hormone replacement therapy may be recommended in women with migraines,

Use of hormone-controlling drugs may explain why women with migraines have such high risk of ischemic stroke, says Nazarian. Contraceptives and other estrogen therapies are both known to contribute to long-term risk factors for cardiovascular diseases and stroke, such as high blood pressure and increased reactivity by clot-forming blood platelets.
References:
1. Saman Nazarian, et al. Migraine headache and the risk of ischemic stroke, a systemic review and meta-analysis of observational studies. Johns Hopkins Medical Institutions.