By Kate Kelland, Health and Science Correspondent
LONDON (Reuters) - Britons are having sex from their teens until well into their 70s and experimenting with experiences and techniques once dismissed as deviant, according to a major series of scientific studies of sexual behaviour.
But while people may have expanded their sexual repertoire over the past decade, both men and women also told researchers they were having sex less often.
"People are working very very hard, they are very busy," said Kaye Wellings of the London School of Hygiene & Tropical Medicine, when asked why she thought people had reported a drop off in average frequency.
The studies, published in The Lancet medical journal, were based on a national survey of sexual attitudes and lifestyles, the first of its kind to get data from people up to the age of 74.
One study also found one in 10 women and one in 70 men said they had been forced to have sex against their will at least once since the age of 13 - a problem that British authorities needed to address urgently, the researchers said.
"We need to start thinking about sex differently - sexual health is not merely the absence of disease, but the ability to have pleasurable and safe sexual experiences, free from coercion," said Wellings, who co-led the series and presented the findings at a briefing in London.
Improving the quality of people's sexual experiences and relationships was also important for their broader health, the researchers added.
"Men and women who enjoy an active sex life are fitter, have lower rates of depressive symptoms and improved cardiovascular health as compared to those who do not," she and fellow researchers wrote in a commentary on the results.
The studies surveyed and analysed data from more than 15,000 people aged 16 to 74.
They also drew on similar surveys conducted in 1990 and 2000, making them among the biggest and most comprehensive examinations of sexual behaviour undertaken in a single country.
Around 57 percent of men aged between 65 and 74 said they had had vaginal sex within the past year, with 30 percent reporting having had oral sex and 3 percent having had anal sex.
A smaller proportion of women in the same age group reported having active and varied sex lives, but in younger age groups the changes in sexual behaviour were more striking among women than among men.
One of the most dramatic findings was an increase from 4 percent in the 1990 survey to 16 percent in the current survey in the proportion of women reporting ever having had sex with another woman.
This change coincides with more tolerance in general of same-sex relationships, the researchers said, although they noted that the studies also found people are becoming less tolerant of married partners having extra-marital sex.
The researchers said the surveys showed Britons in general were moving with the times in term of sex, reflecting a global context in which the separation of sexual activity from reproduction is well under way.
Sexual behaviours that are not essential to conception - including masturbation, oral and anal sex, same sex practices and sex in groups "have become easier to discuss and have gained greater acceptance," they said.
"In many cultural contexts, what was once seen as deviance or perversion is increasingly referred to as diversity."
(Reporting by Kate Kelland, editing by Andrew Heavens)