A new study has found that women with a history of migraines have a significantly lower risk of breast cancer.
"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 Christopher I. Li, a breast-cancer epidemiologist and associate member of the Hutchinson Center’s Public Health Sciences Division.
A history of migraines appeared to reduce the risk of the most common subtypes of breast cancer: estrogen-receptor and/or progesterone-receptor positive.
While not knowing the biological mechanism between migraines and breast cancer, Li and his colleagues guess that it has to do with fluctuations in levels of circulating hormones.
"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.
Pregnancy - a high-estrogen state - is linked with a significant decrease in migraines. "By the third trimester of pregnancy, 80 percent of migraine sufferers do not have these episodes," he said.
In this study, Li and his team combined data from two population-based, case-control studies of 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, which served as a comparison group.
This study is the first of its kind to link migraines and breast cancer, but Li and his researchers have date from two other studies that appear to confirm these findings. "While these results need to be interpreted with caution, they point to a possible new factor that may be related to breast-cancer risk. 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," he said.