Li and his colleagues interviewed 1437 postmenopausal women. Of these, 988 had previously been diagnosed with breast cancer. The women were asked to report the types of menopausal symptoms they had experienced (hot flashes, night sweats, insomnia, mood changes, irregular bleeding, etc.) as well as the duration and severity of the symptoms. Women who had experienced menopausal symptoms were up to 60% less likely to get the two most common types of breast cancer (invasive ductal carcinoma and invasive lobular carcinoma). The more severe the symptoms were, the greater the benefit.
The researchers hypothesize that it’s the same dramatic decrease in estrogen levels that both causes menopausal symptoms and protects against many types of breast cancer. I’m not sure how soothing this information will be to women in the throes of hot flashes. Once their symptoms finally end, they may be glad to have endured them.