Lindsay Friedman, USA TODAY
Insomnia is no longer the only cause for concern in restless leg syndrome victims.
Though the nuisance condition, which causes leg spasms when fatigued, has kept the sandman at bay, new research in the journal Neurology by Xiang Gao, a research scientist at the Harvard School of Public Health, shows that men with the condition faced a 40% higher risk of dying earlier than other men in the study.
"It brings recognition to RLS, which is largely unrecognized and under-diagnosed." Gao says. "It suggests the importance to further understand (the condition)."
In their study, Gao and colleagues tracked more than 18,000 men in their late 60s or older for eight years and found that among 690 with restless leg syndrome, 171, or 25% of the men with the disorder, died in that period. Fifteen percent without RLS died.
To sort out the separate impact of restless leg syndrome, researchers didn't include participants with chronic illnesses such as heart disease, high blood pressure and cancer. Doing that, they found risk of early death was 92% higher among those with RLS than those without. Factors such as weight, sleep disorders, exercise or eating habits had little effect on the initial outcome of the study. Gao says it's "unlikely those uncontrolled factors could explain such big effects."
The exact cause for the disorder or why it would raise a person's risk of dying earlier than normal has yet to be determined. That, Gao says, "is the next question to answer."
According to the National Institute of Neurological Disorders, approximately 10% of the American population may have the disorder though the majority remain undiagnosed. In prior research, Gao found men with the condition aren't the only ones facing bleak outcomes, as women are more likely to develop RLS, which is linked to a higher risk of developing heart disease.
Previous studies tell a different story. An analysis of four earlier studies in late 2012 from researchers in the USA and other nations found that RLS didn't raise the odds that someone might die earlier than normal.
One of the authors of those studies, András Szentkirályi, a research fellow at Germany's Semmel University's Institute of Behavioral Sciences, says he "questions the results," noting the previous four studies looked at a general population while Gao's study focused on a narrower group, Szentkirályi says he would "exercise caution if the most recent study is to be applied to the general population."
"Even with these differences, I was surprised that there were such strong relations between RLS and mortality," he says. "There still is no explanation for these findings or how to further treat it. ... We need more research."
Consequently, uncovering the explanation for RLS and its effects has proved tricky, especially when considering patients with multiple conditions. The answer will reveal itself only with more research and time, says William Ondo, professor of neurology at the University of Texas' Health Science Center.
"The issue with these studies is when you look for other confounding illnesses it's always problematic," he says. "It's always going to be debatable."