By Megan Brooks
NEW YORK (Reuters Health) - Women who suffer from migraine headaches appear to be at much higher risk of developing multiple sclerosis (MS) than women in the general population, according to research released in advance of the American Academy of Neurology Annual Meeting to be held in Toronto in April.
However, it remains unclear whether migraine is a risk factor for developing MS or if it is a condition that occurs at the same time as MS.
Moreover, in an email to Reuters Health, study investigator Dr. Ilya Kister emphasized that "over 99% of migraineurs will not develop MS, since MS is a rare disease, while migraines are quite common; about one in 5 women in the US will have a migraine over the course of a year."
The study involved over 116,000 women who were part of the Nurses' Health Study II (NHS-II). At enrollment in 1989, about 18,000 women in the NHS-II had been diagnosed with migraine. During 16 years of follow up, 375 women in the study developed MS, including 82 in the group with physician-diagnosed migraine at the outset.
The study found that women with physician-diagnosed migraine at the beginning of the study were 47 percent more likely to develop MS than women without a diagnosis of migraine.
There are a number of reasons why migraine might be more common in people with MS. "One explanation is that migraine can, in some cases, be viewed as a symptom of MS," said Kister who is with New York University School of Medicine. "Alternatively, higher frequency of migraine could be due to an intermediate variable, such as depression, as both migraine and MS are associated with higher rates of depression, or to an MS medication, (particularly interferons), which may have migraine as a side effect."
However, it's also possible that migraine is one of the factors that predispose a person to develop MS, the researcher added.
What causes MS is unknown, but research has revealed a number of possible genetic and environmental risk factors. "Our work suggests that migraine may be another risk factor for multiple sclerosis," Kister told Reuters Health.
The researcher would like to see closer study of the relationship between migraine and MS. One outstanding question is whether migraine affects the course of MS, Kister said.
In the meantime, because migraine is common in MS patients, often disabling, overlooked and yet potentially treatable, Kister suggests that doctors elicit a "headache history" from all MS patients.