Migraine is the most common form of headaches in young adults, especially women. The headaches are thought to affect as many as 25 percent of all women in their mid- to late 30s. Some studies have suggested that adults with a history of migraines could also be at risk for stroke. One explanation could relate to decreased blood flow to the brain seen with migraines, which is also a factor when artery blockages cut off blood to the brain resulting in a stroke. Millions of women also take oral contraceptives, and some evidence suggests that the pills could also raise stroke risk, especially in women who smoke. If migraines and strokes are related, migraines earlier in life could help predict potentially debilitating or fatal strokes later on.

What the researchers wanted to know: Are adults who suffer from migraines at a greater risk for strokes later on? Do different kinds of migraines carry different levels of risk? Does the use of oral contraceptives add to stroke risk in women with migraines?

What they did: Researchers analyzed 14 studies of stroke in migraine sufferers conducted between 1975 and 2004. Most of the studies had hundreds of participants, though three had only a few dozen stroke patients for comparison.

What they found: Overall, people who suffered migraines were 2.16 times more likely to have strokes later than those who did not have the headaches. Those who routinely suffered visual blockages called auras along with their headaches had slightly higher stroke risk, while those without auras had a slightly lower risk. Three studies suggested that migraine suffers using oral contraceptives could have nearly a nine times higher stroke risk than controls, though other studies have put the risk closer to two times.

What the study means to you: Migraines could be a risk factor for later strokes in adults, especially in women who also take oral contraceptives.

Caveats: The connection between oral contraceptives and stroke in migraine sufferers could be important to millions of women but needs much more study, the researchers said.

Find out more: The National Institute for Neurological Disorders and Stroke has information on stroke and its risk factors. The National Headache Foundation has fact sheets on migraines and stroke.

Read the article: Etminan, Mayhar, et al. "Risk of Ischemic Stroke in People With Migraine: Systematic Review and Metaanalysis of Observational Studies." British Medical Journal. Published online Dec. 13, 2004.