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

Area of Science:

• Neuroscience
• Sleep Medicine
• Neurology

Background:

• Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by dream enactment and loss of muscle atonia during REM sleep.
• RBD is considered a prodromal stage of alpha-synucleinopathies, potentially stemming from brainstem dysfunction.
• The full spectrum of REM sleep alterations in RBD remains incompletely understood.

Purpose of the Study:

• To investigate alterations in REM sleep microstructure in patients with isolated RBD and Parkinson's disease (PD) + RBD.
• To compare REM sleep features, including phasic REM sleep, sawtooth waves, and NREM/REM transitions, between patient groups and controls.

Main Methods:

• Retrospective analysis of 20 patients with isolated RBD, 20 with PD+RBD, and 20 controls.
• Manual scoring of REM sleep without atonia, rapid eye movement bursts, and sawtooth waves.
• Comparison of REM sleep microstructure parameters using a general linear mixed-effects model.

Main Results:

• Phasic REM sleep proportion was elevated in isolated RBD compared to controls and PD+RBD.
• Non-REM/REM sleep transition duration increased progressively from controls to isolated RBD to PD+RBD.
• Sawtooth wave density and duration were reduced in PD+RBD versus controls, with altered spectral content in both patient groups.

Conclusions:

• REM sleep dysregulation in RBD extends to specific electrophysiological features beyond atonia loss and dream enactments.
• Findings highlight broader microstructural REM sleep changes in RBD, including altered phasic activity and transitions.
• The observed gradient in NREM/REM transitions suggests a potential progression of sleep abnormalities in RBD.