WASHINGTON, D.C. (Reuters):

There's more bad news for those pudgy couch potatoes, junk food junkies and TV devotees - and this time it really hits them where it hurts.

A study published on Thursday found that about 18 per cent of United States men age 20 and up suffer from erectile dysfunction - and the condition is strongly linked to a sedentary lifestyle of little physical exercise, poor diet and lots of television.

Not surprisingly, the condition was most common in older men.

But there was a strikingly high prevalence in men with diabetes and high blood pressure.

"This really means that staying active - moving more and eating less - and staying healthy, in addition to being good for your cardiovascular health may also be good for your sexual health," said epidemiologist Elizabeth Selvin of Johns Hopkins University in Baltimore, who led the study, in an interview. "It's just another reason to get off the couch and exercise."

The study in the American Journal of Medicine sought to get a sense of the prevalence of erectile dysfunction, formerly called impotence, in what Selvin called "the post-Viagra era".

The U.S. government approved Pfizer Inc.'s Viagra in 1998 as the first pill for erectile dysfunction - the inability to attain an adequate penile erection for satisfactory sexual activity. The arrival of Viagra not only provided a treatment option, but boosted awareness of the formerly taboo subject and made it more acceptable to discuss.

The study estimated that 18.4 per cent of U.S. men age 20 and older - about 18 million - have the condition. Among those ages 20-39, 5.1 per cent had it; ages 40-59, 14.8 per cent; ages 60-69, 43.8 per cent; and age 70 and older 70.2 per cent.

Half of the men in the study who had diabetes also had erectile dysfunction. Nearly 90 per cent of men with erectile dysfunction had risk factors for cardiovascular disease, including diabetes, high blood pressure, poor cholesterol levels or smoking, the study found.