A few days ago The North American Menopause Society (NAMS) issued a press release entitled “Persistent Hot Flashes May Lead to Increased Risk of Breast Cancer” issuing the results of an 18-year study by the Women’s Health Initiative which studied the “association between persistent vasomotor symptoms and breast cancer incidence and mortality.”
“In this large group of women who were not users of hormone therapy, persistent hot flashes and night sweats for 10 or more years were associated with a slight but significant increase in breast cancer incidence,” says Dr. JoAnn Pinkerton, NAMS executive director. “Other risk factors included an elevated body mass index of more than 30 and current alcohol use. More studies are needed in women who have persistent hot flashes to understand their cardiovascular and cancer risks.”
The long-term study was comprised of nearly 25,499 postmenopausal women aged 50-79 years old. Of those women, 1,399 were diagnosed with breast cancer. Those who had persistent vasomotor symptoms (VMS), which include hot flashes, flushes, and night sweats, had a higher incidence compared to those who never experienced such postmenopausal symptoms.
The increased risk is slight, but statistically significant. The results of the study say women with persistent VMS have a hazard ratio of 1.13. But what does that mean in layman terms?
A hazard ratio of 1 means that the two groups being studied have an equal likelihood of an event occurring, in this case breast cancer. If the risk of breast cancer were twice as likely, the hazard ratio would be 2.
The silver lining is that persistent VMS at least doesn’t appear to affect the survival rate. The hazard ratio for breast cancer survival was 1.02, which is slight, but statistically insignificant.
An important part about this study is that it studied women who were not using hormone therapy. Breast cancer is specifically influenced by the hormones estrogen and progesterone, so current and former users already have an increased risk. By studying those who were not using hormone replacement therapy, they eliminated this variable from influencing the study.
The exact mechanism by which the menopausal depletion of estrogen causes hot flashes is not yet fully understood. Normally the body stays within a small range, fluctuating in a circadian rhythm, but during a hot flash the body thinks it is suddenly hotter than it is and does its best to cool itself off. The more superficial veins (those closer to the surface of the skin) dilate to increase the blood flow and allow heat to dissipate via sweating and consequently the body cools.
How these vasomotor responses are connected with an increased risk of breast cancer is not yet known, but if you are experiencing long-term menopausal symptoms, talk to your doctor and be aware of any other risks you may have.