US researchers have recently confirmed the findings of an earlier smaller study they published last year that suggested women with a history of migraine are likely to have a lower risk of developing breast cancer. They estimated that among both premenopausal and postmenopausal women with a clinical diagnosis of migraines, the risk of getting breast cancer was 26 per cent lower compared to women without a history of migraines.
The new research was led by Dr Christopher I. Li, a breast-cancer epidemiologist and associate member of the Public Health Sciences Division of the Fred Hutchinson Cancer Research Center in Seattle, Washington. As first author, Li and colleagues from other research centers in the US, have published the work as a paper in the July issue of Cancer Epidemiology, Biomarkers and Prevention, a journal of the American Association for Cancer Research.
The authors noted that both migraine and breast cancer are diseases that involve hormones, and therefore it is not unreasonable to hypothesize that the two could be linked. However, to date only one small study, the one they published last year, has investigated this, and it was unable to explore the link in sufficient detail, especially in terms of menopausal status and triggers for migraine that are known risk factors for breast cancer, such as alcohol and hormone therapy.
For this study, Li and colleagues used data covering nearly 10,000 women, half of whom had breast cancer and the other half were controls, who were taking part in a multicenter population-based case-control study in the United States where any history of migraine was recorded in structured interviews (as opposed to self-reports or filling in questionnaires).
This time their findings showed that the reduction in risk was much the same for pre- and postmenopausal women, and was independent of how old sthey were when migraine was diagnosed or what type of prescription drugs they used. They also found that avoiding migraine triggers such as alcohol, smoking and hormone replacement therapy (HRT) made no difference to the risk.
The main differences between this study and the earlier one that suggested the link are:
* Much bigger group: more than four times the size (the earlier one had about 2,000 participants).
* The group was more geographically diverse: the data came from women living in five metropolitan areas instead of only one.
* The group's age range was wider: from 34 to 64 years old as opposed to 55 to 74 in the earlier study. This helped the researchers better estimate pre- and postmenopausal effects.
* Researchers were better able to study migraine triggers from data on the women's lifestyles.
Regarding the triggers, which the earlier study had not been able to look at properly, and left the researchers wondering if avoiding migraine triggers might also reduce a woman's chances of developing breast cancer, this study helped them to eliminate that factor.
"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.
However, what is still a mystery is how a history of migraine protects women against developing breast cancer.
"We know that migraine is definitely related to hormones and that's why we started looking at this in the first place," said Li said.
"We have different ideas about what may be going on but it's unclear exactly what the biological mechanisms are," he added.
Li and colleagues have now started a follow up investigation in the same group to find out if type, timing, intensity and severity of migraine makes a difference.
In the meantime the researchers are about to publish a third study that showed the link between migraine and breast cancer risk was unaffected by whether the migraine sufferers took non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen. Other studies have suggested these drugs are linked to reduced risk of breast cancer. Thank you for reading :)
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