In an odd twist of fate, women who suffer migraines are at significantly lower risk for breast cancer, a new study finds.
Researchers don't know why this would be the case, but they suspect it has to do with hormone fluctuations. Estrogen, for example, was already known to stimulate the growth of hormonally sensitive breast cancer. And migraines have been tied to changes in hormone levels.
"We found that, overall, women who had a history of migraines had a 30 percent lower risk of breast cancer compared to women who did not have a history of such headaches," said Dr. Christopher I. Li, a breast-cancer epidemiologist and associate member of the Hutchinson Center's Public Health Sciences Division.
The study is detailed in the November issue of the journal Cancer Epidemiology, Biomarkers and Prevention.
In particular, migraine headaches reduced the risk of the most common types of breast cancer, in which tumors have estrogen and/or progesterone receptors, or docking sites, on the surface of their cells, which makes them more responsive to hormone-blocking drugs than tumors that lack such receptors.
"Migraines seem to have a hormonal component in that they occur more frequently in women than in men, and some of their known triggers are associated with hormones," Li said. "For example, women who take oral contraceptives — three weeks of active pills and one week of inactive pills to trigger menstruation — tend to suffer more migraines during their hormone-free week," he said.
Conversely, pregnancy — when estrogen levels are high — is associated with a significant decrease in migraines.
"By the third trimester of pregnancy, 80 percent of migraine sufferers do not have these episodes," he said.
While this study represents the first of its kind to look at a potential connection between migraines and breast cancer, Li and colleagues have data from two other studies that in preliminary analyses appear to confirm these findings, he said.
"While these results need to be interpreted with caution, they point to a possible new factor that may be related to breast-cancer risk," he said. "This gives us a new avenue to explore the biology behind risk reduction. Hopefully this could help stimulate other ideas and extend what we know about the biology of the disease."
The study involved 3,412 Seattle-area postmenopausal women, 1,938 of whom had been diagnosed with breast cancer and 1,474 of whom had no history of breast cancer. Information on migraine history was based on self-report and was limited to migraines that had been diagnosed by a physician or other health professional.
The research was funded by the National Cancer Institute.