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By Denise Mann

WEDNESDAY, March 10, 2010 (Health.com) — Some might call it a fair trade: Women tend to live longer than men, but men have longer—and better—sex lives in their later years, new research shows.

Older men are more likely than their female counterparts to be sexually active, to have a good sex life, and to crave sex, according to a study based on two large national surveys that included more than 6,000 people.

Although both men and women become less sexually active as they age, women appear to do so at a faster rate. Thirty-nine percent of men between the ages of 75 and 85 said they were having sex, compared to 17% of women in the same age bracket, the study showed.

In the same age group, 41% of men and 11% of women said they were "interested in sex." Men of all ages also rated the quality of their sex life higher than women did.

Staying healthy seems to be the key to keeping the fire alive in your golden years. The healthier older men and women are, the more sex they are likely to have and the more years they will have it, according to the study, which was published in the British Medical Journal.

“This is a good reason to stay healthy and keep your partner healthy,” says lead researcher Stacy Tessler Lindau, MD, an associate professor of obstetrics and gynecology at the University of Chicago. “Sex is a really important issue, but we don’t take it into account when measuring quality of life. Now we can.”

Dr. Lindau and her colleagues developed a new statistic, "sexually active life expectancy," which is exactly what it sounds like: how many years of sex you've got left. They calculated the measure by combining survey data on age, reported level of sexual activity, and how healthy the respondents considered themselves to be.

When it comes to sex, the normal life-expectancy patterns are reversed, the researchers found. At age 55, men have 15 more years of sexual activity to look forward to, on average, while women have just 10.6 years.

There is some good news: As with your overall life expectancy, healthy living can add years to your sex life. Men over age 55 who stay in very good or excellent health gain five to seven extra years of sexual activity, while women who stay healthy gain up to six years, Dr. Lindau and her colleagues estimated.

“People in relationships should continue to have sex until the age of 99,” says Ruth Westheimer, better known as Dr. Ruth, the sex therapist, radio and TV personality, and author of books including Dr. Ruth's Sex After 50. “The older generation has to be reeducated that sex at later ages is not dirty or something to be laughed at, but to be cultivated."

Next page: Women tend to outlive their partners

One reason why older women are less sexually active than men may be because they don’t have a partner, or because their partner is no longer healthy enough to have sex. “Women outlive their marriages and their relationships,” Dr. Lindau says.

She and her colleagues found that as women aged, they were far less likely than men to be married or living with a partner. In one of the surveys the authors used, just 58% of the women ages 65 to 74 had a partner, compared to 79% of men in the same age bracket. Among 75- to 85-year-olds, 72% of men still had a partner, compared to just 39% of women.

When women did have a partner, they were almost as likely as their male counterparts to be sexually active, although they tended to give their sex lives lower marks than men did. In every age group included in the surveys, a smaller percentage of women than men described their sex life as "good" overall.

“Some women are sexually active to please their partners, and some may feel that they can’t say no,” Dr. Lindau says.

Dennis Lin, MD, a psychiatrist in the psychosexual medicine program at Beth Israel Medical Center, in New York City, says that the gender differences reported in the study may reflect cultural attitudes in addition to health or demographic factors.

“In our society, women are brought up in a way that they are not supposed to ask for or want to have sex, and this is certainly true in older women," Dr. Lin says. "So they may be reporting that they don’t want sex because they are too modest to admit that they do."

Dr. Lindau agrees that "the stigma that society attached to older women and sexuality" may have shaped the survey data. The opposite may also be true: Older men may exaggerate the amount of sex they are having.

And just because women aren't having sex with a partner doesn't mean their sexual needs aren't being met, Westheimer points out. “Some couples find it easier to masturbate rather than engage in sexual activity,” she says. “The researchers should now go back and do another study and find out about masturbation.”

Older women without a partner "should get a vibrator,” she adds.

The study was far from exhaustive. As the authors note, the study didn't follow individuals over time, and only considered heterosexual couples. Still, it drives home the fact that health and sex go hand in hand.

“Health-care providers need to assess sexual activity and the quality of the sexual activity in [their] patients,” says Dr. Lin. “If you are not sexually satisfied, doctors can make referrals to improve your sex life.”