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Background: Circadian symptom manifestation in the evening and night is one of the main characteristics of restless legs syndrome (RLS). Although the inverse temporal course of corticosteroid rhythm and RLS symptom severity is obvious [lower cortisol level associated with increased RLS severity], this relationship has yet to be studied.

We investigated the effect of late-evening application of exogenous cortisol (hydrocortisone) on sensory leg discomfort (SLD), one of the main complaints of patients with RLS.

Methods: Ten untreated patients with idiopathic RLS participated in the study. Change of SLD was rated on a visual analogue scale during the 60 minutes resting period of the so-called Suggested Immobilization Test. Patients received either hydrocortisone 40 mg or placebo (saline) IV in random order in a double-blind crossover design, with 1 week between the experiments.

Results: Severity of SLD was lower during hydrocortisone infusion than during placebo (p = 0.032). Though blind to the experimental condition, 5 of the 10 patients experienced improvement in symptoms during hydrocortisone administration, but no patient felt an amelioration during the placebo condition.

Conclusions: Our data indicate a probable physiologic relationship between evening and early night hour restless legs syndrome symptom increase and low cortisol level. [Cortisol levels are typically cyclical - higher in early morning and lower at night.]

Source: Neurology. 2008 Apr 29;70(18):1620-2. PMID: 18443313, by Hornyak M, Rupp A, Riemann D, Feige B, Berger M, Voderholzer U. Center for Sleep Research and Sleep Medicine, Department of Psychiatry and Psychotherapy, University Medical Center, Freiburg, Germany. [E-mail: magdolna.hornyak@uniklinik-freiburg.de]