Summary: A new UCL study finds that women who are sexually active at least monthly have a lower risk of entering menopause early compared with women who report sex less frequently.
Source: UCL
Weekly or monthly sexual activity is linked to a later age of natural menopause compared with sexual activity less than monthly, according to a new study using data from the Study of Women’s Health Across the Nation (SWAN).
Researchers found that women reporting weekly sexual activity were 28% less likely, at any given age, to have reached menopause than women reporting sexual activity less than monthly. For the purposes of the study, sexual activity included sexual intercourse, oral sex, sexual touching and caressing, and self-stimulation.
The research, published in Royal Society Open Science, uses data from SWAN — the largest and most diverse longitudinal cohort available for studying the menopausal transition in the United States. The study examined how sexual frequency relates to the timing of natural menopause and tested competing explanations for observed differences in menopausal timing.
Lead author Megan Arnot (UCL Anthropology) explains: “If a woman is not having sex and pregnancy is unlikely, the body may reduce investment in ovulation because ovulation is costly and unnecessary in the absence of conception. This could reflect an energetic trade-off in which the body reallocates resources that would otherwise support ovulation toward other activities, such as caregiving.”
The idea that ceasing fertility can free women to invest in kin is related to the Grandmother Hypothesis. That hypothesis proposes menopause evolved in humans to reduce reproductive conflict between generations of females and to increase inclusive fitness by enabling post-reproductive women to help raise grandchildren.
Because ovulation temporarily alters immune function and increases susceptibility to infection, the physiological cost of continued ovulation may outweigh its benefits when the chance of pregnancy is low. In such cases, delaying or ending ovulation may be advantageous if those resources can support survival or investment in relatives.
The SWAN analysis drew on 2,936 women who formed the baseline cohort in 1996–1997. At the first interview the average participant age was 45. The sample was ethnically diverse but included a plurality of non-Hispanic white women (48%). Most participants had education beyond high school, an average of two children, and a majority were married or in a relationship (78%) and living with their partner (68%).
At baseline none of the women had yet reached menopause. Forty-six percent were in early peri-menopause, showing initial menopause-related symptoms such as changes to menstrual cycles and hot flashes, while 54% were pre-menopausal with regular cycles. Participants reported sexual behaviours and frequency, including whether they had sex with a partner in the past six months, the frequency of sexual intercourse, oral sex, touching or caressing, and whether they had engaged in self-stimulation over that period. The most common frequency reported was weekly (64%).
Over ten years of follow-up, 1,324 (45%) of the cohort experienced natural menopause at an average age of 52. Time-varying Cox models assessed the relationship between sexual frequency and age at natural menopause. Women reporting weekly sexual activity had a hazard ratio of 0.72, while women reporting monthly sexual activity had a hazard ratio of 0.81, both relative to women reporting sexual activity less than monthly. In other words, weekly sexual activity was associated with a 28% lower likelihood of experiencing menopause at any given age, and monthly activity with a 19% lower likelihood, compared with less-than-monthly activity.
The analysis controlled for multiple potential confounders, including oestrogen levels, education, body mass index (BMI), race, smoking status, age at menarche (first menstrual period), age at the first interview, and overall health.
The study also tested whether simply living with a male partner — used as a proxy for exposure to male pheromones — affected menopause timing. No relationship was found between cohabiting with a male and later menopause, which provides no support for the pheromone hypothesis in this dataset.
Senior author Professor Ruth Mace (UCL Anthropology) noted: “Menopause is an unavoidable life stage, and there is no behavioural intervention that will prevent reproductive cessation. Still, our results suggest the timing of menopause may be partly responsive to the likelihood of becoming pregnant, indicating a potential biological flexibility in reproductive ageing.”
Funding: The research received support from the Economic and Social Research Council and the Biotechnology and Biological Sciences Research Council.
Source:
UCL
Media contacts:
Natasha Downes – UCL
Image source:
Image adapted from the UCL news release.
Original research: Open access. Title: “Sexual frequency is associated with age of natural menopause: results from the Study of Women’s Health Across the Nation.” Authors: Megan Arnot and Ruth Mace. Published in Royal Society Open Science.
Abstract
Sexual frequency is associated with age of natural menopause: results from the Study of Women’s Health Across the Nation
Previous observations have shown married women tend to experience a later age of natural menopause (ANM) than unmarried women, but the reasons for this association have not been clear. This study tested whether sexual frequency could mediate the link between marital status and ANM by influencing the body’s investment in continued ovulation in response to the likelihood of conception. The analysis used data from 2,936 women across 11 waves of SWAN, employing time-varying Cox regression. The study found no evidence supporting a pheromone-based explanation but did find that women reporting weekly sexual activity were 28% less likely to reach menopause than women reporting sexual activity less than monthly, suggesting that ANM may be somewhat facultative in response to pregnancy likelihood.