Objective: The aim of this study was to examine the cognitive profile in a large cohort of patients with idiopathic REM sleep behavior disorder (iRBD).

Background: iRBD is a parasomnia characterized by a loss of muscle atonia during REM sleep. iRBD is considered as a major risk factor for Parkinson’s disease (PD) or dementia with Lewy bodies (DLB). Few studies have extensively measured cognitive functions in iRBD and all were done on relatively small sample of patients.

Methods: One hundred and fifty-six polysomnography-confirmed iRBD patients (age: 68.29±7.51 years; education: 13.25±3.84 years) and 155 healthy subjects (age: 67.39±7.99 years; education: 13.75±2.90 years) participated to the study. All participants underwent a comprehensive neuropsychological assessment including tests measuring five cognitive domains: 1) attention, 2) executive functions, 3) language, 4) visuospatial abilities, and 5) learning and memory.

Results: iRBD patients performed worst than healthy subjects on attention [Trail Making Test part A (p≤0.01), Digit Span (p≤0.027), and Coding (p≤0.001) subtests of the WAIS-III] and executive functions [Stroop inhibition (p≤0.002) and flexibility (p≤0.022) conditions, Trail Making Test part B (p≤0.001), letter (p=0.011) and semantic fluency (p≤0.001). iRBD patients had also worse performance than controls on verbal learning and memory [the Rey Auditory-Verbal Learning Test: sum of trials 1 to 5 (p≤0.001), list B (p≤0.001), immediate recall (p≤0.001), delayed recall (p≤0.001), and recognition (p≤0.001)]. However, no significant between-group difference was found for non-verbal memory (immediate and delayed recalls of the Rey Complex Figure Test). Moreover, Vocabulary subtest of the WAIS-III (language) revealed no significant between-group difference. Finally, visuospatial abilities, measured by the copy of the Rey Complex Figure Test, the Block Design subtest of the WAIS-III, and Bells test (number of omissions) also revealed no significant between-groups differences.

Conclusions: iRBD is characterized by impairment in attention, executive functions, and verbal learning and memory with a preservation of language, non-verbal memory, and visuospatial abilities. These results are consistent with the cognitive profiles of PD patients with mild cognitive impairment and patients with mild DLB. Future studies are needed to specify which cognitive domains could be markers of conversion to PD or DLB in iRBD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-cognitive-profile-of-idiopathic-rem-sleep-behavior-disorder/