The number of sexual partners Britons have will change as they age, researchers have found.
The findings are part of a new study shedding light on people's sex lives as they get older.
The study found gay and bisexual men over 70 were more likely to have had more than one sexual partner recently than straight men of the same age.
It showed they continued to have sex with multiple partners, while straight men and women became less sexually active.
University of East Anglia, King's College London and University College London surveyed more than 5,000 adults during the 2022 mpox (previously known as monkeypox) outbreak, in an effort to look at how sexual behaviour changes with age, so they could develop scientific models for sexually transmitted infections.
Lead researcher Dr Julii Brainard, from UEA's Norwich Medical School, said: "Before this study, many models about sexually transmitted diseases assumed that everyone over a certain age, say 40 or 65, stopped being sexually active, or at least stopped having multiple partners.
"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."
Some 5,126 British adults were questioned, which included 3,297 sampled from the general population and 1,036 men who have sex with men (MSM) from Facebook and Instagram between 5 September of 6 October last year, with an additional 831 people responding to adverts on the gay dating app Grindr.
Women who have sex with women, and other relationship types, were discounted due to the small numbers responding.
Most people questioned had either zero or one sexual partner at any age in the preceding three weeks, with 65% of straight women saying they only had one partner in the last three weeks until they were 50, before a steep climb to no partners.
Some 79% of straight women over 70 had no male partners in the preceding three weeks.
Meanwhile, half of straight men in all age groups reported having one partner in the previous three weeks, but were more likely to report no partners as they got older.
For heterosexual men over 70 who have slept with a woman in the last three months, half did not have a sexual partner in the preceding three weeks.
That falls to 44% for straight men under 70.
Having more than one recent partner, or partner concurrency, was found to be uncommon among the general population, but common among social media respondents.
Some 42% of MSMs spoken to on Facebook and Instagram, and 52% of Grindr respondents, had at least two recent male sexual partners - with that number falling as people got older.
In MSM respondents over 70, 17% reported having more than one sexual partner in the most recent three weeks, rising to 25% for those recruited on social media.
That compares with 2% of straight people over 70 reporting the same.
Dr Brainard said: "Most people in our survey, regardless of their gender identity or sexuality, had zero or one recent partner at any age.
"We managed to collect a lot of data from MSM who practised partner concurrency.
"About 45% of them sustained partner concurrency from age 27 to 63.
"Even at age 65+ the respondents recruited via social media still tended to have more sexual contact than the general population sample at the same age.
"It would be interesting to see if these findings were replicated if we targeted heterosexuals most likely to practise partner concurrency.
"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."
Researchers will be hoping they can tailor safe sex messaging to the right groups using the correct channels in the future.
This study, published in the Plos One journal, was funded by the National Institute for Health and Care Research.