In the United States, between 5 and 15 percent of the population is living with the lifelong condition, which currently has no cure.
The illness tends to affect women and elderly adults more than the rest of the population.
A new study, led by Xiang Gao — an associate professor of nutritional sciences at Pennsylvania State University in State College — investigates the link between RLS and mortality related to cardiovascular disease (CVD) among women.
CVD is the leading cause of death among both men and women, with 1 in 4 deaths in the U.S. being related to a condition of the heart.
Women with RLS at 43 percent higher risk
Gao and colleagues examined data on 57,417 women, which was available from the Nurses' Health Study, a prospective study of women's health.
The women were aged 67, on average, and did not have any cancer, renal failure, or CVD at the beginning of the study. They were clinically followed for a period of 10 years.
Every 2 years during this time, the women were administered questionnaires inquiring about RLS, other medical conditions, and lifestyle factors.
During this follow-up period, 6,448 deaths were recorded. The team applied the Cox proportional hazards model in order to calculate the heart-related death risk while adjusting for age, chronic illness, and other factors that could influence the results.
The analysis revealed that women who had been diagnosed with RLS had a higher risk of CVD-related mortality. Specifically, over the 10-year study period, women with RLS were around 43 percent likelier to die from a heart condition than with those without RLS.
Additionally, the longer the women had had RLS for, the higher was their risk of CVD-related death.
No links were found between RLS and mortality caused by other conditions, such as cancer.
The authors conclude, "Women with RLS had a higher CVD mortality rate, which may not be fully explained by common co-occurring disorders of RLS."
Risk independent of co-occurring illnesses
So, to eliminate the possibility that these co-occurring conditions may be responsible for CVD death rather than the sleep disturbance itself, Gao and team excluded women with these conditions from their study.
This made the statistical effect of RLS on heart-related death even stronger. Gao says, "People with RLS are at elevated risk of CVD and other chronic conditions, but previous studies of all-cause mortality in people with RLS have reported inconsistent results."
"Our research clarifies how restless leg[s] syndrome affects cardiovascular disease-related mortality in older women, specifically."
"This study suggests that RLS could be a novel risk factor for CVD-related death," adds Gao.