NEW YORK -- A new study found that erectile dysfunction is common among older American men -- even men who do not have prostate cancer.

The study, which was published in this week's Annals of Internal Medicine, suggests older men with a healthy lifestyle and no chronic disease have a lower risk for erectile dysfunction. The new study examined data on more than 31,000 men aged 53 to 90.

"In our research, we defined erectile dysfunction, or ED, as the inability to have or maintain without treatment, an erection adequate for intercourse," said Dr. Eric Rimm from the Harvard School of Public Health. "In our study, the largest of its kind, we found that men under age 60, almost three-quarters of these men had adequate function. Yet as men aged, that decreased, and we found that men 85 or older, only 10 percent of them still had adequate function."

According to the study, about one-third of all men over age 50 in the United States will experience erectile dysfunction. The study also showed that many aspects of sexual function, including desire and overall ability, decrease more each decade after age 50.

But the study suggests that men can reduce their risk for erectile dysfunction by increasing their exercise and spending less time watching TV, by losing weight if overweight, quitting smoking, and drinking alcohol moderately.

"We found a wide range of the ability to have good erectile function of men into their mid-80s to early 90s, and those men that maintained the best function were those that exercised, did not smoke, maintained a healthy weight and also had very little sedentary activity, that is did not watch television that much," Rimm said.

While some lifestyle modifications may help lower the risk for erectile dysfunction, there are some risk factors that cannot be modified.

"Risk factors for ED that can't be modified are aging, diabetes or other chronic diseases like cancer or stroke," Rim said. "However, what we found is that if you maintain a healthy lifestyle, your risk of ED as you age can be strongly modified."