TUESDAY, Jan. 5 (HealthDay News) -- Men with restless leg syndrome are more likely to have erectile dysfunction, new research suggests, but it's not clear how the two conditions are related.
"There is an association, but we don't know which one comes first," said study author Dr. Xiang Gao, an instructor in medicine at Harvard University School of Public Health. If researchers do discover how they're connected, it could lead to more effective treatments, he said.
Restless leg syndrome "afflicts a significant portion of our population and in a minority of cases can cause insomnia and other important consequences," said Dr. Robert Vorona, an associate professor at Eastern Virginia Medical School in Virginia who studies sleep disorders.
Its causes remain a mystery, Vorona said, but some evidence suggests it's related to reduced levels of iron and the neurotransmitter known as dopamine in the brain. Those who have the neurological disorder complain of an almost irresistible urge to move their legs.
In the new study, published Jan. 1 in the journal Sleep, Gao and colleagues examined responses from 23,119 medical professionals, including physicians, veterinarians and pharmacists, who were asked questions about restless leg syndrome in 2002.
Of the men surveyed, 395 reported having restless legs at least 15 times a month. They were more likely than the other men to use antidepressants and more likely to smoke.
After researchers adjusted their statistics to reduce the effect of age on the results, they found that those with the most restless leg syndrome symptoms were about twice as likely to suffer from erectile dysfunction. The rate was still higher after the researchers adjusted their figures to account for the effects of other factors, such as antidepressant use and smoking.
The research doesn't prove that one of the disorders causes the other. And something else -- perhaps a third disease that boosts the risks of both -- could explain the link.
"There is an association between these two conditions, but we still don't know the exact mechanism," Gao said. His team said further research is warranted.
Vorona said another sleep disorder -- sleep apnea -- also has been linked to erectile dysfunction. And patients with erectile problems appear to do better when their sleep apnea is treated, he said.
As for the current study, Vorona said it makes sense that the two conditions might be linked "on a physiological basis," perhaps through dopamine.
Indeed, dopamine has been linked to both restless leg syndrome and erectile dysfunction, Gao said. "Dopamine plays an important role in many aspects of human health," he added.
Learn more about restless leg syndrome from the National Institutes of Health.
SOURCES: Xiang Gao, M.D., Ph.D., instructor, medicine, Harvard University School of Public Health, Boston; Robert Vorona, M.D., associate professor, Eastern Virginia Medical School, Norfolk; Jan. 1, 2010, Sleep