WEDNESDAY, June 15 (HealthDay News) -- Men who struggle with restless legs syndrome face a higher risk of impotence, a new study suggests.

The study, by researchers from Harvard University, builds on earlier research by the scientists that found that impotence, or erectile dysfunction, was more common among older men with restless legs syndrome -- and the more frequent the symptoms of the sleep disorder the higher the risk of impotence.

For the new study, the researchers started with more than 11,000 men, with an average age of 64 at the start of the trial in 2002, who did not suffer from impotence, diabetes or arthritis. The trial, called the Health Professionals Follow-up Study, began with the men answering a standardized set of health-related questions.

Men were considered to have restless legs syndrome (RLS) if they met four RLS diagnostic criteria recommended by the International RLS Study Group and had symptoms more than five times a month.

The researchers went on to identify 1,979 cases of erectile dysfunction. And men with restless legs syndrome were approximately 50 percent more likely to become impotent, compared to men without the syndrome, even after the researchers compensated for the participants' age, weight, whether they smoked or used antidepressants, as well as the presence of several chronic diseases.

Men who experienced restless legs syndrome symptoms up to 14 times a month were 68 percent more likely to struggle with erectile dysfunction, the study found.

The research was presented at SLEEP 2011, the annual meeting of the Associated Professional Sleep Societies, in Minneapolis. Because the study was presented at a medical meeting, the conclusions should be viewed as preliminary until published in a peer-reviewed journal.

In the Jan. 1, 2010, issue of the journal Sleep, the same researchers reported that erectile dysfunction was more common among older men with restless legs syndrome than those without RLS, and the link was stronger among men with a higher frequency of restless legs symptoms.

"The mechanisms underlying the association between RLS and erectile dysfunction could be caused by hypofunctioning of [the brain chemical] dopamine in the central nervous system, which is associated with both conditions," study lead author Dr. Xiang Gao, an instructor at Harvard Medical School and an associate epidemiologist at Brigham and Women's Hospital in Boston, said at the time.

According to the U.S. National Library of Medicine, restless legs syndrome triggers a powerful urge to move the legs, which become uncomfortable when lying down or sitting. Some people describe it as a creeping, crawling, tingling or burning sensation. Moving makes your legs feel better, but the relief doesn't last. Typically, there is no known cause for restless legs syndrome. In some cases, it can be caused by a disease or condition, such as anemia or pregnancy. Caffeine, tobacco and alcohol may make symptoms worse.

More information

To learn more about restless leg syndrome, visit the U.S. National Institutes of Health.