Women with physician-diagnosed restless legs syndrome (RLS) have a higher risk of dying from cardiovascular causes than their healthy counterparts, a study published this month in Neurology states.

RLS affects anywhere between 5 and 10 percent of the adult population, corresponding author Xiang Gao, MD, PhD, and colleagues wrote in the study, and involves an incessant urge to move the legs while at rest. Since this scratch can only be itched through activity, RLS can affect patients’ sleep patterns and quality of rest, particularly at night.

Previous research has linked RLS and cardiovascular disease (CVD) risk in the past, Gao et al. said, but those trials suffered from small population samples and information gaps. And though RLS is more prevalent in women than in men, the only study exploring a potential link between CVD mortality and RLS recruited solely male patients.

Gao and his team used information from the Nurses’ Health Study (NHS) cohort, which was established in 1976 and has been active for decades. With more than 121,000 patients enrolled, the database encompasses nurses between the ages of 30 and 55 from 11 U.S. states. The researchers focused on a group of 57,417 women without cancer, renal failure or CVD at the trial’s baseline in 2002, and 2 percent of the group reported physician-diagnosed RLS before the study began.

During a follow-up period of a decade, Gao and co-authors reported, the team documented 6,448 deaths in the sample population. Of these mortalities, 1,125 were caused by CVD, 1,943 were cancer-related and 3,380 were due to varying causes.

In an age-adjusted model, the researchers initially found women with RLS had a higher total risk of mortality when compared to those without the condition, but adjusting for additional potential confounders like antidepressant use, vitamin supplements and history of chronic disease all but eliminated that association.

What remained strong throughout the study was the tie between CVD mortality and RLS—women with RLS had a 43 percent higher risk of CVD than those without it, and that statistic held true, with the link strengthening the longer a woman reported experiencing RLS.

Female patients living with RLS were more likely to be white, older, have a higher BMI and have a greater prevalence of chronic disease like hypertension and diabetes, according to the research. These women were also more likely to suffer from sleep disorders and use antihypertensives and antidepressants.

The authors wrote they aren’t sure of why the link between RLS and CVD exists, but they don’t believe it’s due to presence of RLS comorbidities like snoring, short or prolonged sleep duration, Parkinson’s disease, diabetes mellitus or arthritis.

“The mechanisms by which RLS may predispose to CVD and cardiovascular-specific mortality remain unknown,” they said. “RLS-related poor sleep quality and duration may increase the activation of inflammatory cytokines such as serum C-reactive proteins, which contribute to CVD development and have been observed to be related to higher blood pressure, CHD and CVD mortality.”