Rating of daytime and nighttime symptoms in RLS: validation of the RLS-6 scale of restless legs syndrome/Willis–Ekbom disease

Abstract Background The International Restless Legs Scale (IRLS) is the most widely used of the scales rating the severity of restless legs syndrome/Willis–Ekbom disease (RLS/WED). It has been well validated and is the primary end point for most of the therapeutic and nontherapeutic studies of RLS/WED. It has excellent psychometric properties, although it does not capture the severity of RLS under a wide variety of circumstances and times of day. Moreover, the IRLS has a large placebo effect. Methods The Restless Legs Syndrome-6 Scale (RLS-6), however, takes another potentially valuable approach. Six items are rated on a 0–10 scale from no symptoms at 0 to very severe at 10. In addition to questions on satisfaction with sleep and sleepiness, the scale rates the severity of RLS for the past week under four separate circumstances: while falling asleep, during the night, during the day while sitting or lying, and during the day when moving around. The purpose of the current study is to report the validation of the RLS-6 under baseline and therapeutic conditions. Results The RLS-6 seems to be an acceptable, reliable, precise, valid, and responsive instrument for the assessment of RLS severity in a specific and pragmatic manner. Conclusions At present, we view the RLS-6 not as a replacement for the IRLS but as a supplement, as each scale provides information not captured by the other.