We’ve all heard that men reach their sexual peak at 18 and women reach theirs at 28 – so what does that mean for people who are in their 70s and 80s?

Results of a new survey may surprise you.

Researchers at the University of Chicago studied 3,000 elderly American men and women who lived at home and not in nursing homes. What they found was that more than three-quarters of men and half of women between the ages of 75 to 85 are still interested in sex, Reuters reported.

"It's not age per se; that when you get to 80 it's all over with," sociologist Edward Laumann, said in a telephone interview with the news agency.

"It's driven by more proximate factors such as if you become obese, or you're smoking too much, or you contract diabetes. Medications can depress sexual interest. The aging process itself is not a major factor driving these results.”

A non-existent sex life should also serve as a warning sign, Laumann said.

"If sexual health goes to hell, it may be a canary in the mine shaft. It may be a sign of health problems.”

And there’s always the issue of finding a partner to have sex with – which can be especially hard for the elderly.

Among women aged 70 and older, 70 percent have outlived or are separated from their spouses. Among men in that age group, 35 percent have lost a long-time partner, according to the report.

But, there is some good news on this front. Last month, Swedish researchers reported that 70-year-olds of both sexes are having more sex than they did 30 years ago.

Click here to read more about this story from Reuters.