According to the research, published by the Institute for Family Studies, 20 percent of married Americans, aged over 55, admit to extra-marital sex, compared to just 14 percent of those under 55, reports the Independent.
It's easy to assume that this is simply because older people are likely to have been married longer and have thus had more time to cheat - the majority were married between 20 and 30 years - but the study reveals that instances of adultery in older marriages have soared since 2000.
At the same time, the rate of extra-marital sex amongst 18-55-year-old married couples has declined, showing a divergence.
There's also the possibility that the findings reflect a rise in polyamory or "ethical non-monogamy" i.e. having sex with other people with your partner's consent.
The research, titled 'America's New Generation Gap in Extramarital Sex, was led by Nicholas H. Wolfinger, a professor in the University of Utah's Department of Family and Consumer Studies.
"No matter how many polyamorists there are today, old-fashioned adultery seems to have risen among older Americans," Wolfinger says.
The majority of people still disapprove of extra-marital sex - overall the rate has remained constant at around 16 percent of people cheating on their spouses over the last 30 years - but attitudes are relaxing.