Migraines (search), which are most common in young women, have long been considered a possible indicator of stroke risk. The latest research indicates that those who experience grayed or blacked-out vision are at almost double the risk of stroke.

Those who see spots, lines or flashing lights for several minutes also had more risk.

Overall, women in this study who didn't have vision problems with their migraines were at no greater risk for stroke, although previous studies reached a different conclusion.

An estimated 24 million to 32 million Americans have migraines, and researchers have long been interested in examining the link between the two.

The latest research, based on a study of 1,000 women between ages 15 to 49, was presented Thursday at a meeting of the American Stroke Association by Dr. Steven Kittner, a neurology professor of at the University of Maryland School of Medicine and a researcher at the VA Medical Center in Baltimore.

He and his colleagues emphasized that stroke is rare among people under age 50, whether they have migraines or not. Women aged 15 to 49 make up only about 2 percent of the 700,000 U.S. residents who have strokes each year.

In a telephone interview, Wayne H. Giles of the Centers for Disease Control and Prevention, who worked with Kittner, cautioned that mini-strokes called transient ischemic attacks also can have symptoms such as fuzzy, blacked-out vision. "We need to be sure what we're looking at is a symptom related to migraine rather than a transient ischemic attack," he said.

Dr. Larry Goldstein, director of Duke University's stroke center, echoed that, saying all the vision symptoms can have other causes which should be investigated rather than assuming they are caused by migraines.

Kittner and other doctors said that small though the stroke risk is, people who have migraines with any vision problem should reduce other stroke risks by avoiding cigarettes, exercising and making sure their diet is healthy.

An Italian study also presented at the conference found that migraine sufferers were almost twice as likely to have strokes as those without the headaches. It didn't distinguish between those with vision problems and those without. However, researcher Massimo Camerlingo, head of the neurologic unit at Policlinico San Marco in Osio Sotto, Bergamo, noted that all the migraine sufferers in his study did experience some vision problems.

An article published last month in the British Medical Journal looked at 14 studies of migraine and stroke. That analysis found that, overall, migraines doubled the risk of stroke and migraines with vision problems almost tripled it.