Cognition, mood and anxiety in ESRD-patients with and without restless legs syndrome

Introduction: Restless legs syndrome (RLS) is a common complaint of patients with end-stage renal disease (ESRD). There is also evidence of a high prevalence of unrecognized cognitive impairment and increased levels in depression and anxiety in the dialysis population. The purpose of the current study was to examine differences in mood and cognitive performance between ESRD- patients with and without RLS.

Material and methods: Data from 122 patients regulary undergoing dialysis treatment were collected from five dialysis centers. RLS was confirmed in all patients by an expert. ESRD- patients who passed the Mini Mental State Examination with >25 were classified into three groups: Control subjects; RLS subjects without RLS medication; and RLS subjects on medication. Each patient completed several questionaires regarding sleep (PSQI, ESS), mood and anxiety (BDI, STAI, SCL 90). Neuropsychological tasks tapping planing ability (Tower of Hanoi) and verbal fluency (phonematic, semantic) were performed by every patient after a dialysis session. Medical history and standard laboratory values were obtained for all subjects.

Results: RLS was apparent in 37,1% of ESRD patients. 35 RLS patients received medications known to affect RLS symptoms. Suprisingly, treated RLS- patients showed more severe RLS symptoms than untreated RLS-patients according to the IRLS scale (IRLSG: 27.1±7.8 vs. 21.9±7.8; JHRLS 2.3±0.9 vs. 2.1±0.8). Treated RLS patients also scored higher on depression and anxiety scales than controls (BDI: 17, 3±10,7 vs. 9.9±6.8; SCL 90 depression: 0.83±0.75 vs. 0.50±0.46; STAI 1: 42.7±14.2 vs. 34.5±9.3; STAI 2: 42.7±13.5 vs. 35.2±9.7; SCL 90 anxiety: 0.77±0.66 vs. 0.25±0.29), while untreated RLS patients did not differ from the controls. For the neuropsychological tasks no systematic differences between RLS patients and controls could be detected.

Conclusion: In a sample of ESRD patients we could confirm the high prevalence of RLS in this population. Unexpectedly, treated RLS- patients suffered from more servere restless legs complaints than the untreated RLS subjects. The increased depression and anxiety scores in treated RLS patients could be related to the severity of the symptoms. Overall, there was no convincing evidence for a systematic cognitive impairment in association to RLS. However, further studies with even more sensitive cognitive tasks may be needed to clarify this issue.