Decreased sleep spindle density in patients with idiopathic REM sleep behavior disorder and patients with Parkinson's disease

Objective: To determine whether sleep spindles (SS) are potentially a biomarker for Parkinson's disease (PD). Methods: Fifteen PD patients with REM sleep behavior disorder (PD + RBD), 15 PD patients without RBD (PD - RBD), 15 idiopathic RBD (iRBD) patients and 15 age-matched controls underwent polysomnography (PSG). SS were scored in an extract of data from control subjects. An automatic SS detector using a Matching Pursuit (MP) algorithm and a Support Vector Machine (SVM) was developed and applied to the PSG recordings. The SS densities in N1, N2, N3, all NREM combined and REM sleep were obtained and evaluated across the groups. Results: The SS detector achieved a sensitivity of 84.7% and a specificity of 84.5%. At a significance level of alpha = 1%, the iRBD and PD + RBD patients had a significantly lower SS density than the control group in N2, N3 and all NREM stages combined. At a significance level of alpha = 5%, PD - RBD had a significantly lower SS density in N2 and all NREM stages combined. Conclusions: The lower SS density suggests involvement in pre-thalamic fibers involved in SS generation. SS density is a potential early PD biomarker. Significance: It is likely that an automatic SS detector could be a supportive diagnostic tool in the evaluation of iRBD and PD patients. (C) 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.