How our number of sexual partners changes as we age

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A new study involving UCL that aims to inform mathematical models of sexually transmitted infections shows how the number of sexual partners we have changes as we age, with some surprising findings.

A team from the UCL Institute of Health Informatics, the University of East Anglia (UEA) and King’s College London surveyed more than 5,000 people aged 18 years and older during the 2022 mpox (previously known as "monkeypox") outbreak.

The researchers wanted to better understand how sexual behaviours change with age, so that mathematical models of sexually transmitted infections can be made more accurate. Key findings included in the paper, published today in the journal PLOS ONE, show that many gay and bisexual men over age 70 continue to have a sex life with multiple partners, while straight women become less sexually active after age 50.

Co-author Professor Henry Potts (UCL Institute of Health Informatics) said: " It’s not just about the average person, but about the range of behaviour we see. People of all ages and sexualities can have different sex lives. We need to make sure that this is reflected when we are modelling what can happen in a public health context and when we’re planning healthcare "Or there might be an assumption that young people have the most sex. But the answer is more nuanced, and it partly depends on people’s sexuality."

The study is based on a survey of 5,164 British people, including 3,297 sampled from the general population and 1,036 men who have sex with men (MSM) recruited via Facebook and Instagram. A further 831 people responded to adverts on the gay dating app Grindr.

"The 2022 mpox cases spread mostly among men who have sex with men, so we particularly surveyed this group," explained Dr Brainard.

The participants were asked for their gender, sexual identity (gay, bisexual or heterosexual) and how many sexual partners they had had in the last three weeks and in the last three months. The answers were divided into the three largest groups that each had more than a thousand responses: women who have sex with men, men who have sex with women, and men who have sex with men.

The team focused on the relationship between sex partner counts in last three weeks and respondent age, using statistical models to see how much a person’s age was linked to their recent partner count.

Key findings:

About 65% of heterosexual women reported having one partner in the last three weeks consistently until they were 50 - after which there was a steep climb in reporting no partners. 79% of women age 70+ who identified as heterosexual or had any male partners in last 3 months, had had no male partners in the last three weeks.

Of the heterosexual men surveyed (all age groups), 50% reported having one partner in the last three weeks. But they were increasingly likely to report no partners as they got older. 50% of men age 70+ who were heterosexual or had had sex with any women in last three months, didn’t have a female partner in the most recent three weeks, compared to just 44% of men having heterosexual sex who had no recent female partners when age under 70.

Partner concurrency - which is more than one recent sex partner - was uncommon in the general population, but common among the social media samples. 42% of MSMs recruited on Facebook or Instagram and 52% of Grindr respondents had at least two recent male partners.

Partner concurrency declined among older people, with least decline among social media respondents. Seventy-seven men who have sex with men, age 70+, answered the survey. 17% of them reported more than one recent partner in the most recent three weeks. 25% of the MSM age 70+ recruited via social media had concurrent partners.

Dr Brainard said: "Models of disease spread shouldn’t assume that young people are necessarily most at risk or that having multiple partners just stops happening at a strict age threshold."

The information about age profiles and sexual habits is useful because it helps to tailor safe sex messages at the right demographics and using media channels that best reach these subgroups.

Research Fellow Dr Louise Smith from King’s College London coordinated the survey in autumn 2022 to collect "Further research into other minority sexualities and gender identities could be beneficial to better understand the granularity of sexual behaviour and optimal public health messaging suited to different groups of people in the UK."

Mark Greaves

E: m.greaves [at] ucl.ac.uk
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