REM sleep microstructure alterations in REM sleep behavior disorder: beyond muscle tone

These results reinforce the hypothesis that rapid eye movement sleep dysregulation in rapid eye movement sleep behavior disorder extends to rapid eye movement-specific electrophysiological features beyond loss of atonia and dream enactments. Statement of Significance This study compared rapid eye movement (REM) sleep microstructure between patients with isolated REM sleep behavior disorder (iRBD) or RBD associated with Parkinson's disease (PD + RBD), and controls. We found some altered REM sleep features in the patient groups vs. controls, as increased phasic REM sleep proportion in iRBD and reduced sawtooth waves (STW) density and duration in PD + RBD. Both groups exhibited altered STW spectral characteristics with a shift toward higher frequencies. Additionally, we observed a gradient in the duration of non-rapid eye movement/REM sleep transitions, increasing from controls to patients with iRBD and peaking in patients with PD + RBD, who exhibited the longest transitions. These findings highlight that REM sleep anomalies in RBD extend beyond atonia loss and dream enactments, encompassing broader microstructural changes.