Change of International Restless Legs Syndrome Study Group Rating Scale subscales with treatment and placebo: a pilot study

Abstract

Background:

In 2003, the 10-question International Restless Legs Syndrome Study Group Rating Scale (IRLS) was developed as a means of assessing the severity of restless legs syndrome. Two subscales were identified: symptom severity (SS 1) and symptom impact (SS 2). Only one study has investigated the subscales’ responsiveness to a 12-week treatment with ropinirole. This current study was undertaken to assess the impact of a 4-week, non-pharmaceutical treatment on the two subscales and to explore whether or not both subscales were impacted by the observed placebo effect.

Methods:

The pooled data from questionnaires of 58 patients (41 from both treatment groups and 17 from the sham treatment control group), who participated in two clinical studies, were reviewed. Their change in score over a 4-week trial was computed. The average change in both subscales in both groups was computed and t-tests were performed.

Results:

In the treatment group, the average scores of both subscales changed significantly from baseline to week 4 (P<0.005 for both). Compared to the control, SS 1 changed (P<0.001), but not SS 2 (P=0.18). In the sham treatment group, the scores for SS 1 changed significantly (P=0.002), but not for SS 2 (P=0.2).

Conclusion:

This study corroborated findings from an earlier study in which both subscales changed with a 12-week drug treatment. It also showed that the observed placebo effect is attributed to a small but significant change in symptom severity, but not symptom impact.

Keywords::

• restless legs syndrome
• RLS severity scale
• IRLS subscales
• symptom impact
• symptom severity

Author contributions

UHM: research project conception, organization and execution; statistical analysis execution, review, and critique; manuscript preparation: writing of first draft, review, and critique. SCH: research project organization; statistical analysis review and critique; manuscript preparation: writing of first draft, review, and critique.

Disclosure

The authors declare no conflicts of interest in this work.

Supplementary materials

Figure S1 International restless legs syndrome questionnaire.

Note: Adapted from Sleep Medicine, Vol 4, Hening WA, Allen RP, Restless legs syndrome (RLS): the continuing development of diagnostic standards and severity measures, 95–97.¹ Copyright © 2003, with permission from Elsevier.