"Many of the triggers of migraine in women are known to be hormonally related, and also are important in the development of breast cancer," Christopher Li, MD, of the Fred Hutchinson Cancer Research Center in Seattle, tells WebMD. "We now see a plausible relationship between hormones and migraines and breast cancer."
The study, published in the November issue of Cancer Epidemiology, Biomarkers & Prevention, shows that women with a history of migraines have a 30% lower risk of breast cancer than women not diagnosed with the headaches.
Li, the lead author of the study, says the biological mechanism behind the association is not fully known, but it likely has to do with fluctuations in the 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," he says. "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."
But pregnancy, a high estrogen state, is associated with a significant decrease in migraines, he tells WebMD. And estrogen, he adds, is known to stimulate the growth of hormonally sensitive breast cancer.
The researchers combined data from two studies of 3,412 postmenopausal women (aged 55 to 79 years old) in the Seattle area, including 1,938 who'd been diagnosed with invasive breast cancer and 1,474 women without breast cancer. Information on migraine history was limited to cases diagnosed by health professionals.
"Women who reported a clinical diagnosis of migraine had a 33 percent reduced risk of IDC [invasive ductal carcinoma ] and a 32 percent reduced risk of ILC [invasive lobular carcinoma ] compared with women with no history of migraine," the authors write. "These reductions in risk did not vary substantially by age at migraine diagnosis or by history of ever using prescription migraine medications."
Li says the conclusions of the study, the first to look at a possible connection between migraines and breast cancer, should be interpreted with caution, but in an optimistic light.
"This potentially points to new mechanisms that may be related to breast cancer prevention ," he tells WebMD. "If we can uncover what those are, it may lead to new ways to treat breast cancer."
Role of Migraine Medication
Another possible reason women with migraines seem at reduced risk for breast cancer is medications they take to control headache pain , Li says.
"These women may be more frequent users of NSAIDs [nonsteroidal anti-inflammatory drugs]," he says "There is evidence that use of NSAIDs is protective against breast cancer, so part of this reduction could be related to use of that medication, though it is unlikely to account for the whole reduction."
That doesn't mean women should start taking NSAIDs, which include aspirin and ibuprofen , Li says, but further research will explore that possibility.
Len Lichtenfeld, MD, deputy chief medical officer of the American Cancer Society, says the study supports the link between estrogen and hormone-sensitive breast cancer.
"You can't absolutely say for sure that what the researchers are measuring is in fact responsible for higher or lower risk of breast cancer," Lichtenfeld tells WebMD.
The study, he says, points out that postmenopausal women, who are known to have lower levels of estrogen, also have a lower frequency of migraines. "What they are saying here is: this is not just postmenopausal. If you have migraines, it may indicate that you have lower estrogen levels throughout your life. This may explain the findings in this study that women with migranes have a lower risk of breast cancer."
Lichtenfeld says obesity also is related to increased risk of breast cancer after menopause because fat cells produce estrogen. "Some researchers say the higher estrogen levels in the blood are the reason there is an increased breast cancer risk in overweight and obese postmenopausal women."
Li says researchers "were surprised by the magnitude of the reduction in breast cancer" in women with migraines and that the study "is good news in that it identified a potential new protective factor."
For now, he says, women "should just continue their regular screenings."
By Bill Hendrick
Reviewed by Louise Chang
©2005-2008 WebMD, LLC. All rights reserved