The recent study is a follow-up to research published in 2008 that also found migraine headache sufferers have a significantly reduced risk of getting breast cancer. The newer study has thousands more participants from a wider age range than did the previous one.
"It does appear that migraines may protect women from breast cancer, and that it's equally protective for both younger and older women," says Christopher Li, MD, PhD, the lead author of both studies and a breast cancer epidemiologist and associate member of the Fred Hutchinson Cancer Research Center's Public Health Sciences Division in Seattle.
"We see a 26% reduction in risk associated with migraine," he tells WebMD. The study is published in Cancer Epidemiology, Biomarkers & Prevention.
Migraines and Breast Cancer Risk: Study Details
In the previous study, the researchers had evaluated 1,938 women with breast cancer and 1,474 healthy women, all ages 55 to 79, and found up to a 33% reduced risk of breast cancer among the migraine sufferers.
In the newest study, Li and his colleagues compared more than 4,500 women with breast cancer (who had been diagnosed between 1994 and 1998) with more than 4,500 healthy women, all ranging from 35 to 64 years old. The new study also draws from a more diverse geographic area than the old study.
All the women answered the same questions about migraine history, reproductive history, use of hormone therapy or birth control pills, menopausal status, body mass index, alcohol use, and smoking status.
Those women who reported a history of migraine headache that had been diagnosed by a doctor had a 26% decreased risk of breast cancer compared to women without a migraine history, Li found.
The risk reduction remained, Li found, regardless of a woman's menopausal status, age at which migraines were diagnosed, use of prescription migraine medications, or whether she avoided established migraine "triggers" -- including alcohol intake and hormone replacement therapy -- which are also linked with increased breast cancer risk.
The new research rules out many of the other explanations for why women with migraines may have a lower risk of breast cancer, Li says, such as migraine sufferers being less likely to drink or use hormones. "Migraine may in fact be an independent predictor of breast cancer reduction risk," he tells WebMD.
Migraines and Breast Cancer Risk: Why?
It's not known why having migraine headaches appears to lower breast cancer risk, Li says.
Fluctuations in reproductive hormones are thought to explain the link, with migraines often occurring when estrogen drops, Li writes in the study. It's known, for instance, that women on oral contraceptives have more frequent migraines during their hormone-free week, when hormones decline. When women who have migraines get pregnant, many have relief by the third trimester, when estrogen levels rise substantially, he writes.
Migraines and Breast Cancer Risk: Perspective
While the study is well done and there may be an association between migraine and breast cancer risk reduction, "the real connection is unclear," says Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society in Atlanta.
"Could it be hormones? Yes," he says, but adds that it could be other factors as well.
"Postmenopausal women who are obese are at higher risk for breast cancer," he says. "That is thought to be related to the higher circulating estrogen levels." But he says more research is needed to figure out the association between migraines and breast cancer risk reduction.
The potential link between migraines and reduced breast cancer risk does make sense, says Scott Maul, MD, a medical oncologist in Milwaukee who also reviewed the study for WebMD. Higher lifetime exposure to estrogen is a known risk factor for breast cancer, he notes, and some migraines seem to be associated with a drop in estrogen. "But not all migraines are due to hormone fluctuations," he tells WebMD.
"It's hardly a conclusive study," he says. Limitations of the study include the self-report method, which is always subject to participants' less-than-perfect memories.
And migraines are among a multitude of risk factors associated with breast cancer that are under study, he says.
Migraines and Breast Cancer Risk: What's Next
Li agrees that more research is needed. Next, his team will focus on the underlying biology of how migraines may reduce breast cancer risk, hoping the discovery will help them figure out how to reduce risk for non-migraine sufferers as well.
Meanwhile, women with migraine headaches should follow the same preventive breast health steps recommended for women without migraines, Li says. "It really should not change the way they approach breast cancer screening," he says.
Lichtenfeld agrees, noting that women at average risk of breast cancer should begin annual mammograms at age 40.