An unprecedented study of sex and seniors in the United States finds that many older people are surprisingly frisky. Sex and interest in it do fall off when people are in their 70s, but more than a quarter of those up to age 85 reported having sex in the previous year. More than half of those aged 57 to 75 said they gave or received oral sex, as did about a third of 75- to 85-year-olds. Women of all ages were less likely to be sexually active than men. But they also lacked partners; far more were widowed. Half of the people having sex reported at least one related problem. Most common in men was erection trouble (37 %); in women, low desire (43%), vaginal dryness (39%) and inability to have an orgasm (34%). The survey had a remarkable 75% response rate. Only 2% to 7% did not answer questions about sexual activities or problems, although a higher percentage declined to reveal how often they masturbate.