Women who enjoy a healthy sex life will stave off menopause for far longer than those who are less sexually active, a new study suggests.
Researchers at University College London (UCL) found middle-aged women who engaged in sexual activity weekly were 28 per cent less likely to have gone through the menopause during the 10 year follow-up than those who had sex less than once a month.
Happily for singles, sexual activity did not have to include a partner.
In fact, scientists showed that there was no link between later menopause and marriage, or the presence of a male.
Previous theories have suggested that intercourse, marriage, or being in contact with male pheromones, help push back the menopause, because the body thinks there is still an opportunity to have children.
Ovulation is costly for the body, so the expectation is that menopause kicks in as early as possible, if there is no chance of conception.
In evolutionary terms, it meant that a woman, freed from caring for her own children, could then help look after their grandchildren, ensuring the survival of family genes, a theory known as ‘the Grandmother hypothesis.’
Although the new research appears to back up that theory, it shows for the first time that it is not intercourse that is driving the effect.
Doctoral candidate Megan Arnot, of UCL’s department of anthropology, said: “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 energetic trade-off between investing energy into ovulation and investing elsewhere, such as keeping active by looking after grandchildren.
“The idea that women cease fertility in order to invest more time in their family is known as the Grandmother Hypothesis, which predicts that the 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 research is based on data collected from 2,936 women, of an average age of 45, who took part in the US Study of Women’s Health Across the Nation (SWAN) in 1996/1997.
The women were asked to respond to several questions, including whether they had engaged in sex with their partner in the past six months, the frequency of sex including whether they engaged in sexual intercourse, oral sex, sexual touching or caressing in the last six months and whether they had engaged in self-stimulation in the past six months.
The most frequent pattern of any sexual activity was weekly, with 64 per cent saying they had engaged in some form in the past seven days.
None of the women had yet entered the menopause and they were followed up for 10 years, by which time 45 per cent had gone through the change, at an average age of 52.
Those who had sex weekly were 28 per cent less likely to have entered menopause, while even those who sex once a month reduced their chance by 19 per cent.
The difference remained even when taking into account other factors that can influence early menopause, including oestrogen level, education, BMI, race, smoking habits, age at first occurrence of menstruation, and overall health.
The study also tested whether living with a male partner affected menopause as a proxy to test whether exposure to male pheromones delayed menopause.
The researchers found no correlation, regardless of whether the male was present in the household or not.
Last author, Professor Ruth Mace of UCL, added: “The menopause is, of course, an inevitability for women, and there is no behavioural intervention that will prevent reproductive cessation.
“Nonetheless, these results are an initial indication that menopause timing may be adaptive in response to the likelihood of becoming pregnant.”
The research was published in the journal Royal Society Open Science.