Joan Smith: The male-female divide gets worse as you grow older

New research suggests men can expect a longer sex life than women

Wouldn't you know it? Just as the popular press is getting up to speed with the idea that older women enjoy sex – a notion so scary that some have been dubbed "cougars" – a new piece of research suggests that men can expect a longer and more satisfying sex life than women.

You can relax, guys: according to the online BMJ, studies in the US show at least twice as many men as women in the 75-85 age group are still sexually active. And they're said to be enjoying it more.

"Sexual activity, good quality sex life, and interest in sex were higher for men than for women and this gender gap widened with age", the researchers conclude.

Now there's a surprise: a woman who has reached her late 70s or early 80s would have grown up before the sexual revolution and the Pill, both of which drastically changed women's expectations about sex. There are always exceptions, but most of the pre-Second World War generation became wives and mothers at a time when women lacked a language to talk about what they liked and didn't like in bed. Maybe some read The Hite Report and caught up, but my guess is that lots of them didn't.

Then the baby boomers came along and set about deconstructing not just sexual mores but expectations about behaviour at every stage in their lives; the idea that people are elderly in their 60s or early 70s no longer holds, which is why I'm not sure that these studies tell us much about the sexual prospects of people who are currently a lot younger.

Take a high-profile couple like France's President Sarkozy and his glamorous wife Carla Sarkozy-Bruni, for instance: according to the research, Ms Sarkozy-Bruni at 42 has fewer years of active sex life ahead of her than a man of the same age. By the time she reaches 55 (her husband's current age) the gap will be around four years; the President can expect to go on having sex until he is 70 whereas his female peers face a sexual drought at the age of 66.

As it happens, rumours sweeping Paris this week suggest that the marriage of this sexually-adventurous couple is in trouble: Ms Sarkozy-Bruni is said to have found herself a younger man, a 37-year-old musician, while her husband's new love interest is supposedly a 40-year-old female minister in his own Government.

Whether there is a shred of truth in the rumours is unclear; since the French press abandoned its reputation for Gallic restraint, it seems to have become as obsessed with the private lives of celebrities and politicians – the Sarkozy marriage conveniently offers both – as any British red-top.

What is clear is that Ms Sarkozy-Bruni is magnificently unconcerned about her age, appearing at an official function last week in a dress which technically covered her whole body while revealing every curve. She didn't look like a woman who intends to retire from the sexual arena any time soon or indeed at any time at all.

Why should she? Unlike one shame-faced British footballer after another, she has never pretended to value monogamy; she belongs to a generation which seized women's new-found sexual confidence with both hands, at a time when it hadn't yet become fashionable to complain endlessly about young women looking too sexy.

Indeed she should be cheered by another finding from the two studies reported in the BMJ, which is about the impact of good health on older people of both sexes. "Men and women reporting very good or excellent health were more likely to be sexually active compared with their peers in poor or fair health", the researchers found.

At one level, it's a statement of the obvious. Obesity, lack of exercise and poor diet age the body prematurely, predisposing it to cardiovascular disease which damages sexual capacity. Such physical problems affect men more than women, yet it's the latter who are assumed to become less interested in sex as they get older, leading to a dearth of representations of sexually confident older women.

Meryl Streep and Alec Baldwin play for laughs in It's Complicated, Nancy Meyers's film about a divorced older couple having a fling, but there's a striking asymmetry between Baldwin's impish self-mockery and Streep's shyness in revealing her 60-year-old body.

In any case, men can always use Viagra, and the fact that traditionally they choose younger partners works to their advantage. Many women in their 70s and 80s have been widowed, which means that sex is simply no longer an option. You can mock Madonna (51) for her punishing exercise regime and younger boyfriends, but she may be the smart one after all.