Link between migraines and reduced breast cancer risk

10 Jul 2009

Migraines associated with reduced breast cancer risk
Risk did not differ based on a woman’s age
Migraine triggers irrelevant

The relationship between migraine headaches in women and a significant reduction in breast cancer risk has been confirmed in a follow-up study to landmark research published last year. Results of this new study showed a 26 percent reduced risk of breast cancer among premenopausal and postmenopausal women with a clinical diagnosis of migraines.

The study appears in the July issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research. Christopher I. Li, M.D., Ph.D., led the first-of-its-kind study linking migraines with breast cancer risk reduction, which was published in the same journal last November. Li is a breast-cancer epidemiologist and associate member of the Fred Hutchinson Cancer Research Center’s Public Health Sciences Division, in Seattle.

This time, Li and colleagues found that the risk reduction remained statistically similar regardless of a woman’s menopausal status, her age at migraine diagnosis, use of prescription migraine medications or whether she avoided known migraine “triggers” such as alcohol consumption, smoking and taking hormone replacement. These triggers are also well-established breast cancer risk factors.

Some key differences between this study and the initial one in which Li and colleagues discovered the link include:

  • The sample size was more than four times larger this time – more than 4,500 cases and controls versus about 1,000 each in the first study – and was more diverse geographically, drawing women from five metropolitan areas instead of only one. “From an epidemiological perspective, having a larger and more diverse study in its underlying population helps in replicating the finding,” said Li.
  • The age range of women studied was wider this time, 34 to 64 years of age versus 55 to 74 years of age. “We were able to look at whether this association was seen among both premenopausal and postmenopausal women,” he said. “In breast cancer this is relevant because there are certain risk factors that are different between older and younger women. We saw the same reduction in breast cancer risk associated with a migraine history regardless of age.”
  • Researchers were able to ascertain whether women in the study had lifestyle behaviors that are known migraine triggers – alcohol consumption, smoking and taking hormone replacement therapy. They posited that perhaps women who had migraines drank and smoked less and didn’t take hormone replacements. “In this study we looked at women who never drank, never smoked and who also didn’t use hormones and found the same association within each of those groups, suggesting that the association between migraine and reduced breast cancer risk may be independent of those other factors and may stand alone as a protective factor,” said Li.

What remains unknown is why migraines are associated with lower breast cancer risk.

“We know that migraines are definitely related to hormones and that’s why we started looking at this in the first place,” said Li. “We have different ideas about what may be going on but it’s unclear exactly what the biological mechanisms are.”

In the meantime, research on migraines and breast cancer continues. Li and colleagues are conducting a follow-up investigation among the women in the first study to determine the types, timing, intensity and severity of their migraines in hopes that the data may elicit additional clues.

Joanne F. Dorgan, Ph.D., M.P.H., an epidemiologist at Fox Chase Cancer Center in Philadelphia, said that non-steroidal anti-inflammatory drugs are frequently used to treat migraine and these drugs have been associated with lower breast cancer risk in some studies. Additional research is needed to clarify the effect of non-steroidal anti-inflammatory drugs use on the observed association between migraines and breast cancer.

“Estrogen and progesterone are neurosteroids, and investigations into neuroendocrine pathways in relationship to breast cancer risk might also prove to be fruitful,” said Dorgan, who is also an editorial board member of Cancer Epidemiology, Biomarkers & Prevention.