• Ralf Kohnen, Pablo Martinez-Martin, Heike Benes, Claudia Trenkwalder, Birgit Högl, Elmar Dunkl, and Arthur S Walters.
• Posthumously, Research Pharmaceutical Services, Inc, Fort Washington, PA, USA; University of Erlangen, Nuremberg, Germany.
• Sleep Med. 2016 Aug 1; 24: 10-17.

BackgroundDue to the symptoms and the sleep disturbances it causes, Restless Legs Syndrome (RLS) has a negative impact on quality of life. Measurement of such impact can be performed by means of questionnaires, such as the Kohnen Restless Legs Syndrome-Quality of Life questionnaire (KRLS-QoL), a specific 12-item instrument that is self-applied by patients. The present study is aimed at performing a first formal validation study of this instrument.MethodsEight hundred ninety-one patients were included for analysis. RLS severity was assessed by the International Restless Legs Scale (IRLS), Restless Legs Syndrome-6 scales (RLS-6), and Clinical Global Impression of Severity. In addition the Epworth Sleepiness Scale (ESS) was assessed. Acceptability, dimensionality, scaling assumptions, reliability, precision, hypotheses-related validity, and responsiveness were tested.ResultsThere were missing data in 3.58% patients. Floor and ceiling effects were low for the subscales, global evaluation, and summary index derived from items 1 to 11 after checking that scaling assumptions were met. Exploratory parallel factor analysis showed that the KRLS-QoL may be deemed unidimensional, ie, that all components of the scale are part of one overall general quality of life factor. Indexes of internal consistency (alpha = 0.88), item-total correlation (rS = 0.32-0.71), item homogeneity coefficient (0.41), and scale stability (ICC = 0.73) demonstrated a satisfactory reliability of the KRLS-QoL. Moderate or high correlations were obtained between KRLS-QoL scores and the IRLS, some components of the RLS-6, inter-KRLS-QoL domains, and global evaluations. Known-groups validity for severity levels grouping and responsiveness analysis results were satisfactory, the latter showing higher magnitudes of response for treated than for placebo arms.ConclusionsThe KRLS-QoL was proven an acceptable, reliable, valid, and responsive measure to assess the impact of the RLS on quality of life.Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

18 keywords...

hide…