New research from Seattle’s Fred Hutchinson Cancer Research Center suggests women who experience migraines are at 30% less risk of developing breast cancer than women who don’t suffer this type headache. Estrogen is thought to be the link between the two.

Epidemiologist Christopher I. Li, PhD, says migraines often occur when a woman’s natural estrogen levels drop, such as during her menstrual cycle, menopause, or a pregnancy. Migraine-prone pregnant women frequently report fewer migraines during pregnancy, with as much as an 80% drop in migraine occurrences during the final trimester.

Women who have high levels of estrogen are at greater risk of developing breast cancer. Li says women who report migraines are more likely to have low levels of estrogen, a factor thought to reduce the risk of breast cancer.

In the Li study, published in the November issue of the journal, Cancer Epidemiology, Biomarkers & Prevention, 3,412 postmenopausal women were studied, 1,938 of whom had breast cancer while the remaining 1,474 had no breast cancer history. Each woman reported her experience with migraines.

According to Li, migraine sufferers enjoyed a 30% reduced risk of developing breast cancer than the women who never had migraines.

Critics of the Li study include Dr. Ellen Drexler, who says the complexity of both migraines and breast cancer makes it difficult to accept the estrogen link alone. She cites other issues, including genetics, as likely contributing factors and says there is no conclusive evidence that female migraine sufferers have lower estrogen levels than women without migraines. Drexler is associate director of the Maimonides Medical Center’s Division of Neurology in Brooklyn.

Another critic, Dr. Stephen Silberstein, considered a migraine expert who works from the Jefferson Headache Center, Thomas Jefferson University Hospital, Philadelphia, takes issue with the self-reporting of migraines by the women in the Li study. He feels a more scientific method of determining the presence of migraines is needed before any conclusions can be reached.