Binge drinking has become nearly synonymous with college students, but a study out Monday shows a significant, worrisome level of binge drinking among those age 50 to 64 as well.

Working with the National Survey on Drug Use and Health, Duke University researchers report that 22 percent of men and 9 percent of women ages 50 to 64 engaged in binge drinking - five or more drinks at a time - within the past month of the survey. The research, based on a survey of 11,000 men and women that took place in 2005 and 2006, is reported in the American Journal of Psychiatry.

The survey also found that 19 percent of the men and 13 percent of the women had two or more drinks a day, considered heavy or "at-risk" drinking under American Geriatric Society guidelines for older people.

Dan Blazer, the study's lead author and a professor of psychiatry and behavioral science at Duke, says that level of drinking places the older group at more of a health risk than younger counterparts.

"They don't metabolize alcohol as quickly, they may be on medications, or they may have some health problems that alcohol may contribute to," Blazer says. "On average, if a young person drinks five beers and an older person drinks five beers, the older person is almost certainly going to have more difficulty."

The survey also found binge drinking in those over 65: 14 percent of men and 3 percent of women.

In the past, binge drinking has been overlooked by physicians as a health risk because they have been focused on the excessive drinking of young people. But adults in the baby boomer generation could be putting themselves at a greater risk of more serious problems such as stroke, cardiovascular disease, liver disease, neurological damage and poor diabetes control, the Duke research says.

"We typically think of binge drinking as something that occurs with young people such as college students, and here we have examples of older closet drinkers," Blazer says. "Because we don't expect older people to binge-drink, this can be missed by a person's doctor because they are not asking."

The nationally representative study, Blazer says, also found that people don't tend to change such behavior as they get older.

"We may see some younger people's patterns continue and become even more problematic," he says. "You may think that you are more tolerant and your health is just as good or better than it was 20 or 30 years ago, but it's not."