A NEW STUDY from University College London is bound to raise some eyebrows. The researchers focused on the USA’s Study of Women’s Health Across the Nation (SWAN). The investigators examined data collected from nearly 3,000 women. The study is the largest and most diverse longitudinal study available for looking at menopause transition.
Researchers conducted interviews with participants at age 45. On average, the women had two children, and nearly 80 percent were married or in a relationship. The women volunteered whether they had sex with their partner in the past six months, sex frequency (including intercourse, touching, or caressing), and whether the subject engaged in self-stimulation in the prior six months. Sixty-four percent reported weekly sexual activity.
While none of the participating women had entered menopause, nearly half (46 percent) were in early perimenopause. These women had begun to have menopausal symptoms such as changes in their menstrual cycles and hot flashes.
The researchers conducted interviews over ten years. Forty-five percent of the women had natural menopause, at an average age of 52 years. The scientists controlled for estrogen level, body mass index, education level, race, smoking habits, age at the first occurrence of menstruation, overall health, and age at the first study interview.
Here are the striking findings: Women who engage in sexual activity weekly or monthly have a lower risk of entering menopause early than those reporting some form of sex less than monthly.
Numerically, the more sexually active women were nearly one-third (28 percent) less likely to have experienced menopause at any given age. Women who had sex monthly were 19 percent less likely to experience menopause at any given age compared to those who had sex less than monthly.
First author and Ph.D. candidate Megan Arnot observes this:
“The findings of our study suggest that if a woman is not having sex, and there is no chance of pregnancy, then the body ‘chooses’ not to invest in ovulation, as it would be pointless. There may be a biological energy trade-off between investing energy into ovulation and investing elsewhere, such as keeping active by looking after grandchildren.
“The idea that women cease fertility to invest more time in their family is known as the Grandmother Hypothesis. This hypothesis predicts that menopause originally evolved in humans to reduce reproductive conflict between different generations of females and allow women to increase their inclusive fitness through investing in their grandchildren.”
The study authors also note that there is impairment of a woman’s immune function during ovulation, making the body more vulnerable to disease. Pregnancy is unlikely with less sexual activity. It may not be beneficial to allocate more energy to the costly process of menstrual cycles (especially if an alternative is to invest more resources into helping a relative with shared genetics.
Too often, writers do not make clear the bright line that divides association and causality. In this context, I want to point out that this piece in no way establishes causality. Perhaps women having early perimenopausal symptoms such as vaginal dryness were less likely to have sex. Still, I find the association interesting.