Breast Cancer and Estrogen

Breast cancer occurs when mutated cancer cells grow uncontrollably, usually in the ducts and lobules of the breast tissue. A greater lifetime exposure to estrogen increases your risk of breast cancer, so anything that increases estrogen in your body can potentially increase your risk of breast cancer.

Examples of conditions that increase estrogen exposure include:

A longer lifetime number of menstrual cycles (A longer lifetime number of menstrual cycles (starting menstruation prior to age 12 and/or menopause after age 55)Postmenopausal obesity, in which adipose or fat tissue is converted to estrogenCombined hormone therapy, which consists of both estrogen and progestin (the synthetic form of the hormone progesterone)

Migraines and Estrogen

In women, migraine occurrence often varies based on your menstrual cycle, your menopausal state, and whether or not you’re pregnant. This change in migraine frequency and severity may be related to your fluctuating estrogen levels at these times.

For example, migraine frequency often increases immediately before or during a women’s menstrual cycle, referred to as menstrual migraines, when estrogen levels have decreased. On the other hand, many women experience relief of their migraines during the second and third trimesters of pregnancy, a time when estrogen is at high levels.

Since both migraines and breast cancer are estrogen-mediated, there may be a connection between migraine occurrence and a lower risk of developing breast cancer. However, this is controversial due to conflicting evidence.

Studies Showing a Reduced Risk of Breast Cancer

One of the first studies to examine the relationship between breast cancer and migraine was performed in 2008. The researchers, whose findings were published in Cancer Epidemiology, Biomarkers, & Prevention, found that women with self-reported migraines had a 33 percent reduced risk of developing hormone-receptor-positive invasive ductal and lobular carcinoma in the postmenopausal state.

However, the study didn’t control for the use of nonsteroidal anti-inflammatory drugs (NSAIDs), a common class of medications used to treat migraines. Several studies have suggested that NSAID use may, on its own, lower breast cancer risk.

For instance, a 2016 review published in BreastCare found evidence that aspirin and possibly other NSAIDs may decrease the risk of breast cancer and may even help prevent recurrence in women who’ve already had it.

A study from 2010, published in the Journal of Clinical Oncology, also found that postmenopausal women with self-reported migraines had a reduced risk of breast cancer. This study found a 17 percent lower risk of developing invasive hormone-receptor-positive cancers. Like the 2008 study, this reduced risk was independent of NSAID use, as well as the use of alcohol and caffeine, two common migraine triggers.

Another study, this one published in Cancer Causes and Control in 2014, examined over 700 cases of breast cancer. The researchers found that compared to women without a history of migraines, women who had a history of migraines for more than 30 years had a 60 percent lower risk of developing estrogen receptor-positive ductal breast cancer.

In addition, women who had their first migraine before the age of 20 had half the risk of developing estrogen receptor-positive breast cancer (both ductal and lobular) compared to female non-migraineurs. Finally, women with migraine with aura were also about a third less likely to develop either ductal or lobular estrogen receptor-positive breast cancer.

And finally, a 2016 meta-analysis of seven studies involving 17,776 cases and 162,954 participants also found a link between migraine and a decreased risk of both estrogen receptor-positive and progesterone receptor-positive breast cancers. The authors point out that there’s no clear understanding of why, though theories include the estrogen link, a tendency of migraineurs to avoid other risk factors for breast cancer like drinking alcohol and smoking, and the use of NSAIDs to treat migraine.

On the flip side, other studies haven’t found a relationship between a history of migraines and a lower risk of breast cancer.

A 2015 meta-analysis used data from Nurses’ Health Study II participants, identifying 17,696 who reported that their doctors had diagnosed them with migraine. The researchers concluded that there was no evidence of a link between migraine and breast cancer risk, though they did acknowledge that case-control (observational) studies show an association between migraine and a reduced risk of breast cancer. However, they pointed out that prospective cohort studies, which follow people over time, don’t support this conclusion.

A 2018 study of 25,606 Taiwanese women, published in the Journal of Women’s Health, found that not only was there no association between migraines and a decreased risk of breast cancer, but women who saw a doctor four or more times a year for migraine actually had a significantly higher risk of developing breast cancer than those without migraines.

A Word From Verywell

Remember, a link implies a potential relationship or association. It doesn’t mean that one medical condition directly causes or prevents another. As for your own health, stay proactive in your health care. Discuss your risk factors for breast cancer with your physician and review how a healthy lifestyle, such as weight loss and exercise, can reduce your migraines in addition to your risk of breast cancer.