Characterization of Sleep Structure and Autonomic Dysfunction in REM Sleep Behavior Disorder

Abstract

Goal: REM Sleep Behavior Disorder (RBD) is a REM parasomnia that is associated to high risk of developing α-synucleinopathies, as Parkinson's disease (PD) or dementia with Lewy bodies, over time. This study aims at investigating the presence of autonomic dysfunctions in RBD subjects, with and without PD, by assessing their sleep structure and autonomous nervous system activity along the different sleep stages. Methods: To this aim, an innovative framework combining a sleep transition model, by Markov chains, with an instantaneous assessment of autonomic state dynamics by statistical modeling of heart rate variability (HRV) dynamics through a point-process approach, was introduced. Results: In general, RBD groups showed lower HRV than controls across all sleep stages, as well as higher probabilities of transitioning towards lighter sleep stages. Subjects also affected by PD present an even lower HRV, but better sleep continuity. Conclusions: RBD patients suffer from sleep fragmentation and overall autonomic dysfunction, mainly due to lower autonomic activation across all sleep stages. Coexistence of PD seems to improve sleep quality, possibly due to a sleep-related relief of their symptoms.

Keywords: Autonomous nervous system; Markov chains; REM sleep behavior disorder; heart rate variability (HRV); point process.

Fig. 1.

Results for variance , power in the low frequency band , normalized low frequency , power in the high frequency band , normalized high frequency , and sympathovagal balance for the three populations analyzed (CG, iRBD, PD-RBD) across the four sleep stages. For the sake of clarity, results are reported in restricted ranges. For , the range is [0, 1050], outliers up to 3380 msec² are not depicted. For , the range is [0, 1050], outliers up to 2060 msec² are not shown. For , the range is [0, 400] and the outliers up to 980 msec² are not reported. For , the range is [0, 25] and the outliers up to 82 are not depicted. , , and the are unit-less due to their computations. Significance for the within-group analysis is represented as follows: ^*:p<0.05; ^**:p<0.01. In each box, the median of the distribution is represented by the central line, while the 25^th and the 75^th percentiles are the bottom and top edges of the box, respectively. Extreme values that are still considered to fall into the distribution are represented by the whiskers, while outliers are indicated by the circles.