In other words, there may be a common underlying cause for the restless legs syndrome and the higher death rate observed in those with the condition.
"This study suggests that individuals with restless legs syndrome are more likely to die early than other people," said study author Dr. Xiang Gao, an assistant professor at Harvard Medical School and an associate epidemiologist at Brigham and Women's Hospital in Boston. "This association was independent of other known risk factors."
Gao and his team are studying a group of women with the syndrome; he said he doesn't know if the findings from the study of men will be similar in women.
But Gao went on to caution: "[T]his is an observational study," not one that establishes a definite cause-effect relationship. The findings were published online June 12 in the journal Neurology.
The findings corroborate a 2007 study, which found that people with the syndrome were twice as likely to have a stroke or heart disease compared, and the risk is greatest in those with the most frequent and severe symptoms.
39% higher risk
Gao and colleagues studied nearly 20,000 men and found that those with restless legs syndrome had a 39 percent higher risk of an early death than did men without the condition.
Restless legs syndrome is a common condition that causes people to feel an uncomfortable sensation in their legs when lying down, according to the U.S. National Institute of Neurological Disorders and Stroke (NINDS). The feeling may be a throbbing, pulling or creeping sensation. Restless legs syndrome makes it hard to fall asleep and stay asleep.
While the exact cause is unknown, it does tend to run in families, suggesting that there may be a genetic factor.
The condition has been linked to medical conditions including kidney disease and peripheral neuropathy.
Gao noted that many people with restless legs syndrome have low iron levels but he cautioned that consumers should check with their doctor before taking iron supplements, as too much iron can be dangerous, especially in men.
The study followed 18,500 men for eight years. The average age at the start of the study was 67 and at the beginning of the study, none of the men had kidney failure, diabetes or arthritis.
During the study, nearly 2,800 men died. Comparing those with restless legs syndrome to those without, it was found that those with the condition were 39 percent more likely to have died.
Men with restless legs syndrome were more likely to take antidepressant drugs and to have high blood pressure, cardiovascular disease or Parkinson's disease.
Common condition
Restless legs syndrome is a condition that produces an intense, often irresistible urge to move the legs and is a major cause of insomnia and sleep disruption. It affects approximately 10 percent of the U.S. population and about one percent of school-aged children.
In 2007, an international team of researchers identified the first gene associated with the condition.
"We now have concrete evidence that RLS is an authentic disorder with recognizable features and underlying biological basis," David Rye, MD, PhD, professor of neurology at Emory University School of Medicine, director of the Emory Healthcare Program in Sleep, and one of the study's lead authors, said at the time.