Restless legs syndrome, the name given to the considerable discomfort people feel in their lower limbs, accompanied by an irresistible urge to move them, more frequently affects multiple sclerosis (MS) patients than the general public, and significantly impacts sleep quality, a case control study shows.
While the type of MS treatment used was not associated with this syndrome’s presence, it was found to be more likely in patients with greater physical disability and spinal lesions.
The study “Restless Legs Syndrome in Multiple Sclerosis: risk factors and effect on sleep quality – a case-control study,” was published in the journal Multiple Sclerosis and Related Disorders.
Sleep issues, which can affect quality of life, disease severity, and flares, are common in MS patients. Although the precise causes of troubled sleep and increased fatigue are not known with certainty, scientists believe that restless legs syndrome — which typically is felt most while at rest and in the evenings — may play an important role.
A team of researchers at the Medical University of Vienna investigated the prevalence of restless legs syndrome in MS patients being treated at their institution, compared to people without this disease serving as a control group. The team also assessed MS risk factors, and evaluated the influence of disease-modifying therapies (DMTs) on restless legs syndrome.
A total of 117 MS patients (mean age 36.3, 67.5% female), recruited at the MS Clinic of the Department of Neurology between October 2014 and December 2019, and 118 controls (mean age 30.9, 73.1% female), all staff or relatives of workers at the Vienna university, were enrolled.
Patients had a median disease duration of 7.3 years, and most (89.8%) had relapsing-remitting MS, followed by primary progressive MS (6.8%) and secondary progressive MS (3.4%). Their median score on the Expanded Disability Status Scale (EDSS) was 1.5, indicating no evident disability but symptoms are affecting functional abilities; their score range was 0 to 7, spanning from “normal” to wheelchair reliant.
Participants were asked to fill out a number of questionnaires, including the International Restless Legs Syndrome Study Group Rating Scale (IRLSSG), whose 10 questions assess the syndrome’s severity; the Pittsburgh Sleep Quality Index (PSQI), which looks at sleep quality and habits over the previous month; and the Epworth Sleepiness Scale (ESS), which evaluates the likelihood of daytime sleepiness.
Overall, about one quarter of these patients reported restless legs syndrome (23.9%), a proportion seven times higher than that seen in the control group (3.4%). Its intensity was rated as mild for most (79%) of these people.
Excessive daytime sleepiness and poor quality of life were not more common in patients than in controls, the team noted. But scores for these two factors were higher and significantly more common in MS patients with restless legs syndrome than in patients without it — 78.6% vs. 21.3% for impaired sleep; and 32.1% vs. 15.7% for excessive daytime sleepiness.
Patients with restless legs syndrome also had more disability, as reflected in higher the EDSS scores, and a higher frequency of spinal lesions on MRI scans.
Statistical analyses also demonstrated that higher EDSS scores (greater disability) and the presence of MRI lesions were both risk factors for restless legs syndrome in MS patients. But DMT choice had no impact on the severity of restless legs syndrome, daytime sleepiness, or sleep quality.
Among limitations to their study’s findings, the researchers wrote, were data obtained from a single hospital and a relatively small sample size, and the lack of age matching between patients and controls. Patients in this study were also of a younger age with relatively mild disease disability levels, as seen in EDSS scores.
“This may explain the high rate of mild RLS [restless legs syndrome] in our study population, whereas a higher rate of moderate to severe RLS is likely to be found in more advanced MS,” they wrote, adding that research indicates the prevalence of restless legs syndrome doubles every 20 years, peaking around age 65 in patients.
“RLS [restless legs syndrome] should be kept in mind when managing MS patients to avoid delayed diagnosis, misdiagnosis and delayed treatment of both, MS and RLS, thus impeding improvement of quality of life. Moreover, RLS should be considered in each MS patient complaining on chronic fatigue to guarantee the best available symptomatic therapy,” the researchers concluded.
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