Women who experience vision loss as a symptom of migraine have a 70 percent increase in risk of stroke compared to women who don’t have migraines, researchers reported at the American Stroke Association’s International Stroke Conference 2005.
A separate study also reported found that migraines contribute to stroke in young people, independent of the stroke risks presented by alcohol, cigarettes or oral contraceptives.
The first study investigates migraine auras. Migraines are often preceded by aura, a sensory phenomenon such as visual or hearing abnormalities. Migraines with visual aura have been associated with ischemic stroke, but researchers say it is not clear whether a particular type of visual disturbance is more closely linked with increased stroke risk.
Using data from The Stroke Prevention in Young Women Study conducted at the University of Maryland School of Medicine in Baltimore, researchers investigated whether migraine accompanied by visual loss, versus migraine accompanied by lines and spots in the visual field, increased the likelihood of ischemic stroke compared to women without visual symptoms.
Our study found that women who suffer migraines with loss of vision or partial loss of vision were 1.7 times more likely to have stroke compared with women who do not have a history of migraines, said study author Wayne H. Giles, M.D., M.S., associate director for science in the Division of Adult and Community Health at the Centers for Disease Control and Prevention (CDC) in Atlanta.
The study included 963 women, between ages 15 and 49; 542 of them had suffered strokes.
Researchers found that women with migraines without visual symptoms did not have an increased stroke risk. Women who see spots and lines during or just before migraine had a 25 percent increased risk of stroke over women without migraines. But women who experience vision loss during or before migraine had a 70 percent higher risk. This may indicate that vision loss is more likely to represent transient cerebral ischemia than seeing spots and lines.
The prevalence of migraine in general is about 17 percent in women, and the prevalence of migraine with aura, is about 5 percent in women, Giles said. Of those with aura, more than 90 percent of patients report visual symptoms, such as light sensitivity; seeing lines or spots; seeing flashes of light or temporary loss of vision, he said.
Other case-control studies had shown that migraine with aura was more strongly associated with stroke, but ours is the first to examine the type of aura symptom and the likelihood of stroke, Giles said.
These findings need independent confirmation from other investigators, but they indicate that women with migraine and aura should address all other stroke risk factors, particularly smoking. Women with migraine and aura should also be aware that oral contraceptives may increase their risk of stroke, and they should discuss the risk/benefit ratio of these agents with their doctors, Giles said.
Giles emphasized that migraine sufferers who experience new neurological symptoms, including transient loss of vision, should be evaluated by a doctor to exclude other causes such as transient ischemic attack (TIA). A TIA, which is caused by reduced blood flow in the brain, can result in a temporary loss of vision and can occur independent of migraine, he said.
In another study, Italian researchers investigated whether migraine (with or without aura) could be a risk factor for ischemic stroke in patients ages 16 to 44.
Examining data from 238 male and female stroke patients, and an equal number of control subjects (average age 35), researchers recorded participants’ use of contraceptive pills, wine and cigarettes as well as blood pressure, migraine history and cardiac rhythm. Sixty-three stroke survivors had experienced migraines and 33 people in the control group had experienced migraines. Contraceptive pill use, wine intake and smoking habit were not different between the groups.
Analysis showed that those with migraine had 2.7 times the risk of stroke compared to the controls. When migraine was combined with high blood pressure, the stroke risk increased nine-fold, said Massimo Camerlingo, M.D., head of the neurologic unit at Policlinico San Marco in Osio Sotto (Bergamo), Italy. The study was large enough statistically to make assertions regarding stroke in young adults, but it was not large enough to extend those results to all people with migraine.
The role of migraine in precipitating a stroke in young adults appears to be independent from the usual risk factors and from the consumption of wine, cigarettes and the contraceptive pills, he said.