People with migraines may also be more likely to develop blood clots in their veins, according to a study published in the September 16, 2008, issue of Neurology®, the medical journal of the American Academy of Neurology.

In the condition, called venous thrombosis or thromboembolism, blood clots form in a vein, which can limit blood flow and cause swelling and pain. Those clots can then dislodge from the vein and travel to the heart and the lungs, which can be fatal.

For the study, 574 people in Italy age 55 and up were interviewed to determine whether they had a history of migraine or migraine at the time of the evaluation and their medical records were reviewed for cases of venous thrombosis. The arteries in their necks and thighs were scanned with ultrasounds to check for atherosclerosis, or hardening of the arteries.

Of the participants, 111 people had migraine. A total of 21 people with migraine also had one or more instances of venous thrombosis, or 19 percent. In comparison, 35 people without migraine had the condition, or 8 percent.

Researchers do not know why migraine and venous thrombosis are linked. One theory is that the blood of people with migraine may be more prone to clotting.

The study also found that people with migraine are not more likely to have hardening or narrowing of the arteries, which is contrary to a current theory.

"The thinking has been that because people with migraine are more likely to have strokes and other cardiovascular problems, that they would also have more severe and early atherosclerosis," said study author Stefan Kiechl, MD, of Innsbruck Medical University in Austria. "This study is the first to use high-resolution ultrasound to examine this theory, and it provides solid evidence to refute it."