Many people in the UK are having sex from their teens into their seventies, according to a major lifestyle survey.
Researchers who questioned more than 15,000 adults aged 16 to 74 found that for a large proportion sex is now an almost lifelong activity.
The latest National Survey of Sexual Attitudes and Lifestyles (Natsal) survey investigated the sex lives of older individuals in their seventies for the first time.
Among other findings:
- One in six pregnancies in the UK are unplanned.
- At least four out of 10 men and women have had a recent sexual problem, but only a 10th of those interviewed were distressed or worried about their sex lives.
- Lack of interest in sex is one of the most commonly reported problems, and one not confined to women. Around 15% of men had experienced loss of libido.
- Since the last Natsal survey in 2000 people have become more accepting of same-sex relationships but less tolerant of cheating spouses.
- One in 10 women and one in 70 men say they have experienced non-consensual sex.
The survey, the third in the series, was conducted between September 2010 and August 2012.
Professor Dame Anne Johnson, from University College London, who led the research published in The Lancet medical journal, said: "By taking a robust scientific approach to assessing the sexual health and lifestyles of people from across Britain in 2010, and in previous Natsal surveys, we now have a much greater understanding of the role that sex plays over the course of a person's lifetime.
"This new information will help to guide the sexual health and education services that people may need at different stages of their lives. Although our results show that we are improving the uptake of some services, there are other areas where people may need more support and advice on health and sexual problems.
"Positive sexual experiences are related to health and well-being throughout the life course, and it's time for this to be given wider recognition by health workers, educators, and society as a whole.
"We need to do more to create an environment in which it is easier for people to discuss sexual well-being as an integral part of the conversation we have with people about our health."
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Co-author Professor Kaye Wellings, from the London School of Hygiene & Tropical Medicine, said: "The Natsal studies, along with others, reveal major changes in sexual behaviour over the last century, including earlier onset of sexual activity, increasing numbers of older people who are sexually active, a closing of the gap between men and women, and weakened links between sex and reproduction.
"These changes now need to be reflected in research, clinical practice, and education. 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.
"Improving the quality of people's sexual experiences and their relationships will not just improve the effectiveness of sexual health programmes, but is also something that is important in its own right."
Genevieve Edwards, from the family planning services provider Marie Stopes International, said: "Through our services, we meet thousands of women who haven't had access to effective contraception or been given the skills to enjoy the sex lives they want.
"A key insight from the survey is that people are having sex earlier and having children later, which means that, on average, women in Britain spend about 30 years of their life needing to avert an unplanned pregnancy, yet many are not being informed about or offered the full range of services.
"Long-acting contraceptives, for example, can be extremely effective and convenient but too many are never offered the choice."
Paul Ward, acting chief executive of the Terrence Higgins Trust HIV/Aids charity, said: "With more opportunities to have sex than ever before, and more types of sex in our repertoires, we need to make certain that young people have the facts they need to have safe, fulfilling sex lives.
"Sex education in this country is a relic of the last century. Teaching a teenager to put a condom on a banana is no bad thing, but it won't tell them how to deal with being pressured into sex before they're ready, the do's and don'ts of online friendships, or that what they see in porn is not necessarily what a partner wants in the bedroom.
"A decent programme of sex and relationships education, embedded in the curriculum and fit for the 21st century, can help young people have the best, safest sex at the time that's right for them."