SEATTLE (UPI) -- A history of migraine headaches is associated with a significantly lower risk of breast cancer among women, U.S.
researchers said.

Dr. Christopher I. Li and colleagues at Fred Hutchinson Cancer Research Center in Seattle report 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.

Migraine history appeared to reduce the risk of the most common subtypes of breast cancer those that are estrogen-receptor and/or progesterone-receptor positive. Such 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, Li said.

The biological mechanism behind the association between migraines and breast cancer is not fully known, but Li and colleagues suspect 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.

The findings are published in the journal Cancer Epidemiology, Biomarkers and Prevention.