• Michele Terzaghi, Chiara Zucchella, Valter Rustioni, Elena Sinforiani, and Raffaele Manni.
• Sleep Medicine Unit, C. Mondino National Institute of Neurology Foundation, IRCCS, Pavia, Italy.
• Sleep. 2013 Oct 1;36(10):1527-32.

Study ObjectivesTo investigate the capacity of neuropsychological deficits in idiopathic rapid eye movement sleep behavior disorder (iRBD) to predict the development of dementia and/or parkinsonism.DesignProspective longitudinal follow-up study.SettingTertiary sleep center.PatientsTwenty patients with initial iRBD (19 males, mean age 66.1 ± 7.1) underwent a clinical and neuropsychological follow-up within a mean of 43 ± 19 months. Neuropsychological performances at baseline were compared with those of healthy controls matched for sex, age, and education.InterventionsDiscontinuation of clonazepam at least 7 days before the follow-up evaluation.ResultsAt follow-up, the Wilcoxon test showed a significant worsening of scores on Raven Colored Matrices 47 (P = 0.01), Attentive matrices (P = 0.002), phonemic (P = 0.04) and sematic (P = 0.04) fluency. Thirteen patients (65%) showed cognitive deterioration involving multiple domains. Of these, four patients (20%) maintained a stable cognitive dysfunction and nine (45%) showed a progression of cognitive dysfunction: six (30%) in constructional abilities (P = 0.03), four (20%) in short-term memory (P = NS), three (15%) in executive functions and non-verbal logic (P = NS), one (5%) in verbal fluency (P = NS), and one (5%) in long-term memory (P = NS) (McNemar test). Seven patients (35%) retained a normal cognitive profile. Mild cognitive impairment (MCI) was diagnosed at baseline in seven patients (35%). At follow-up, three of these patients showed overt dementia that was accompanied by parkinsonism in all cases; one had worsened from non-amnesic single-domain to nonamnesic multiple-domain MCI, two were stable, and one patient no longer met the criteria for MCI. Four patients (20%) without MCI at baseline had MCI at follow-up. Patients who developed MCI/dementia had an older age at disease onset (65.8 ± 5.4 versus 56.8 ± 9.3; P = 0.01) compared with those who did not.ConclusionsOur findings corroborate evidence that visuospatial abilities constitute the area most affected in idiopathic rapid eye movement sleep behavior disorder (learning as a stable deficit and copying as an evolving deficit). Cognitive deterioration, involving mainly nonverbal logic, attention, and executive functions, can be observed in rapid eye movement sleep behavior disorder follow-up, suggesting an underlying evolving degenerative process. Our data confirm that mild cognitive impairment is frequent in idiopathic rapid eye movement sleep behavior disorder. The presence of mild cognitive impairment predicts the eventual risk of developing dementia, which seemed to be associated with parkinsonism.

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