Americans have a wide sexual repertory and enjoy sex well into their golden years even if the older crowd sometimes take more risks, a major new study revealed Monday.

Those the biggest survey in decades of sexual behavior in the United States was compiled by researchers at the University of Indiana, who documented the sexual experiences and condom use by 5,865 Americans aged 14 to 94.

Pulling together all the information gleaned from their online survey, the researchers found a gender gap and a generation gap in the sex lives of Americans.

Although Americans remain sexually active "well into old age (80+)" only one in five men and one in four women over the age of 50 uses a condom, according to the study, which was published in a special edition of the Journal of Sexual Medicine.

Teenagers, meanwhile, are much more vigilant about condom use, if they are having sex at all - which a majority of US teens are not.

Among sexually active teens, boys said they used a condom 79 percent of the time the last 10 times they had intercourse with a girl, while teen girls reported their partners used one 58 percent of the time, the study found.

Having grown up in the era of HIV/AIDS, teens see condoms as a means of protection against sexually transmitted diseases (STDs) and pregnancy, said Michael Reece, director of the Center for Sexual Health Promotion at the University of Indiana and a lead researcher on the study.

Most Americans over 50, on the other hand - and certainly those who are well into old age - no longer have to worry about pregnancy and see STDs differently to youngsters.

"To many older Americans, STDs are something soldiers returning from war picked up from a prostitute. They're not acknowledged as such a social epidemic," said Reece.

But times have changed and not only are older folks more active sexually, thanks in part to the availability since 1998 of easy-to-take medications like Viagra for erectile dysfunction, but STDs are also more prevalent, he said.

"We may need to re-educate older people because as their relationships end or their partners die, if they're dating and have multiple partners, there may be no danger of pregnancy, but the STD risk is certainly present," Reece told AFP.

As for the teens, Reece said they were "a public health success" and hoped that they would continue to use condoms as they get older.

In addition to the data on condom use, the study found that Americans have become inventive in the bedroom, with study participants reporting a total of 41 combinations of behaviors at their most recent "sexual event," as the study likes to call it.

It also found a gender gap in US adults' sex lives to go with the generation gap in condom use.

For instance, 85 percent of men believed their partner had an orgasm during their most recent "sexual event," but only 64 percent of women said they actually did.

Men also said they were more aroused, had greater pleasure during sex, fewer problems with erectile function, and less pain when they were with their usual partner. Women felt more aroused with a non-relationship partner.

As for masturbation, American men do it "strikingly more" than women, the study found.

But the big news from the study was that masturbation was finally being talked about openly in the United States, former US surgeon general Joycelyn Elders said in a commentary piece published with the study.

"Now it is time to include sex and sexuality as pleasurable and natural in open frank conversation about the human condition," she said.

The study comes 60 years after Alfred Kinsey, also of the University of Indiana, published a groundbreaking survey about sex and nearly 20 years after a nationwide study, published in 1994.

Reece hopes a follow-up study will be done before another 20 years have elapsed, but said it all depends on funding. The current study was funded by a condom maker.