According to the Migraine Research Foundation, around 39 million children and adults in the United States are affected by migraine, a disorder characterized by the recurrence of moderate or severe throbbing pain on one or both sides of the head.
Around 25 percent of people with migraine experience aura, which is a set of neurological symptoms that accompany headache.
Neurological symptoms include visual disturbances, such as colored spots or temporary blindness, dizziness, numbness or tingling on one side of the body, and speech difficulties.
For the new research, co-author Dr. Maria Lantz - of the Department of Clinical Neuroscience at Karolinska Institutet in Sweden - and colleagues investigated whether familial factors might play a role in the possible link between migraine and stroke, as few studies have controlled for this factor.
Stroke risk increased by 27 percent
Dr. Lantz and colleagues analyzed data from the Swedish Twin Registry, identifying more than 53,000 twins who were born between 1935 and 1958 or between 1959 and 1985.
Using data collected from headache questionnaires, the researchers found that a total of 8,635 twins experienced migraine, of whom 5,082 had migraine without aura and 3,553 had migraine with aura.
Over an average 12 years of follow-up, there were 1,297 stroke incidents among the twins.
Compared with twins who did not experience migraine, twins who experienced migraine with aura were 27 percent more likely to have had a stroke during follow-up.
No increased stroke risk was found for twins who had migraine without aura, they report. These findings remained after accounting for a number of stroke risk factors, including blood pressure and smoking status.
Familial factors may exacerbate link
Interestingly, on conducting a twin-pair analysis, the researchers identified familial factors - such as environment during childhood and hereditary factors - that appeared to exacerbate the link between migraine with aura and stroke risk.
Dr. Lantz and colleagues say that their findings support previous studies claiming that migraine with aura may raise stroke risk, and they help to shed light on the factors that might contribute to this risk.
On the other hand, the results may also bring some reprieve to people who experience migraine without aura.
The authors write:
"In conclusion, we observed no increased stroke risk related to migraine overall but there was a modestly increased risk for stroke related to migraine with aura, and within-pair analyses suggested that familial factors might contribute to this association."