Reported August 10, 2007

DALLAS - Recent migraine headaches with visual symptoms often known as "aura" dramatically raise a woman's risk of stroke, researchers reported on Thursday in a study that adds to a growing body of evidence linking the two.

The risks were significantly magnified if women who suffered from migraines with visual problems also smoked or used oral contraceptives, although for young women in this category the chances of a stroke remain small.

"Women with migraines with visual symptoms were at a 1.5 fold increased risk compared to women without migraines," said Dr. Steven Kittner of Baltimore Veterans Affairs Medical Center, who worked on the study.

"However, if the migraine with visual symptoms was within the past year they had a sevenfold increased risk compared to women without migraine," he said in a telephone interview.

Visual symptoms associated with a migraine include zig-zag lines, flashing lights and dark holes that increase in size.

Writing in the American Heart Association journal Stroke, Kittner's team said they looked at 386 women 15 to 49 years old with a first ischemic stroke -- caused by a blot clot blocking blood flow to the brain -- and 614 women of similar ages and ethnicities who had not suffered from a stroke.

Their responses to questions saw the women divided up into three groups: having no migraine; probable migraine without visual symptoms, or probable migraine with visual symptoms.

"Women in this study were young so the absolute risk of stroke was about 20 per 100,000 ... So even if you increase it sevenfold it is still a very small absolute risk," Kittner said.

"So women with migraines with visual symptoms should not become unduly alarmed. However they should reassess all their cardiovascular risk factors such as smoking," he added.

The heart association said migraine and stroke had some risk factors in common, including high blood pressure and patent foramen ovale or PFO.

"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," the AHA said.

Migraines have long been linked to stroke. But the heart association said few studies have addressed the possible reasons, including the potential role of the heart defect.