Heart Rate Variability During Sleep-Related Wake Phases in REM Sleep Behavior Disorder

Autonomic dysfunction can be observed in people with neurodegenerative diseases. This study explores heart rate variability (HRV) in idiopathic rapid eye movement (REM) sleep behaviour disorder (iRBD), RBD patients with Parkinson's disease (PD-RBD), and control group (CG). The focus is on wake states before and after sleep, acquired during overnight polysomnography. A total of 18 CG, 20 iRBD, and 20 PD-RBD subjects, underwent polysomnographic exams with at least 6 hours of sleep. A 5-min ECG signal was obtained during the two awake phases, and analysed for time, frequency, and nonlinear indexes. Non-parametric statistical analysis was employed to evaluate intra-group behaviours. Significant differences were found in time and frequency domain indexes, in PD-RBD and iRBD groups, associated with an increased HRV in the wake after sleep compared to wake before sleep onset (p<0.05 to p<0.0001). Similarly, in the same groups, a significant reduction in nonlinear indexes was found during the last wake stage (p<0.01), but not in CG. As such, RBD may cause an increase in parasympathetic activities in both phases, regardless the presence of Parkinson's disease.