Restless Legs Syndrome Prevalent in IPF Patients, Study Finds

A significant proportion of people with idiopathic pulmonary fibrosis (IPF) were found to have the sleep disorder restless legs syndrome (RLS), compared to a control group, according to new research.

The data also showed that having RLS lowered sleep quality in IPF patients.

The study, “Restless legs syndrome: A new comorbidity in idiopathic pulmonary fibrosis,” was published in the journal Respiratory Medicine.

Though IPF mainly affects the lungs, there are several known comorbidities — or co-occurring conditions — that are associated with the disease.

In previous studies, poor sleep quality has been reported in IPF patients, and conditions such as sleep apnea, nocturnal hypoventilation, and disrupted sleep architectures were identified as causes among these patients.

RLS is a neurological disorder defined by an urge to move the legs. It is considered to be a sleep disorder because the urges occur primarily in the evening and can be triggered by trying to sleep.

Researchers at the Fondazione Policlinico Universitario Agnostico Gemelli IRCCS in Rome, Italy, noted that several IPF patients reported poor sleep quality and an urge to move the legs at night. So, they investigated whether RLS also was a comorbidity of IPF.

“The prevalence of RLS in IPF is unknown, and so is whether it may represent as a significant comorbidity in these patients,” the researchers wrote.

The team compared data from 50 IPF patients (mean age 72 years) registered at their Interstitial Lung Disease (ILD) clinic with data from a control group of 283 people (mean age 69.1 years) referred to the Sleep Disorder Centre at the same hospital.

Patients at the Sleep Disorder Centre were chosen for a control group because detailed information about their clinical sleep conditions and sleep quality was available. These patients were matched to the IPF group by age and gender.

To determine the prevalence of RLS in each group, a validated five-item RLS criteria list was used to diagnose RLS. All diagnoses of RLS in IPF patients were confirmed by a sleep specialist.

Results showed that 12 of the 50 IPF patients (24%) had a confirmed clinical diagnosis of RLS. In the control group, RLS was diagnosed in 31 of 283 people (10.9%).

“As such, the prevalence of RLS was approximately 2.5 [times] higher in IPF patients as compared to the controls,” the researchers wrote.

RLS was found to be of moderate severity in IPF patients, based on the self-rated International Restless Legs Syndrome Study Group (IRLSSG) severity rating scale.

Researchers also found that IPF patients with RLS had significantly reduced sleep quality compared to IPF patients without RLS. This was assessed using the Pittsburgh Sleep Quality Index (PSQI) rating system, a self-rated questionnaire in which a higher score indicates worse sleep quality, and any score of 5 or greater is considered to be poor sleep quality.

Researchers found that a majority of all IPF patients (76%) in the study had poor sleep quality. They also found that the group of IPF patients with RLS reported significantly higher scores (mean 10.6) compared to IPF patients without RLS (mean 6.9).

“Our findings provide first evidence that RLS is a frequent comorbidity in IPF and concurs to further deterioration of sleep quality in these patients,” the researchers wrote.

The team noted that the study was limited to a small number of patients, so the results need to be confirmed in a larger population.

Nevertheless, the study provides evidence that RLS is prevalent in people with IPF, and suggests that “treatment of RLS in patients with IPF could ameliorate [improve] sleep quality and, in turn, quality of life,” the researchers concluded.