Isolated rapid eye movement sleep behavior disorder and cyclic alternating pattern: is sleep microstructure a predictive parameter of neurodegeneration?

Abstract

Objective To evaluate the role of sleep cyclic alternating pattern (CAP) in patients with isolated REM sleep behavior disorder (IRBD) and ascertain whether CAP metrics might represent a marker of phenoconversion to a defined neurodegenerative condition. Methods Sixty-seven IRBD patients were included and classified into patients who phenoconverted to a neurodegenerative disease (RBD converters: converter REM sleep behavior disorder [cRBD]; n = 34) and remained disease-free (RBD non-converters: non-converter REM sleep behavior disorder [ncRBD]; n = 33) having a similar follow-up duration. Fourteen age- and gender-balanced healthy controls were included for comparisons. Results Compared to controls, CAP rate and CAP index were significantly decreased in IRBD mainly due to a decrease of A1 phase subtypes (A1 index) despite an increase in duration of both CAP A and B phases. The cRBD group had significantly lower values of CAP rate and CAP index when compared with the ncRBD group and controls. A1 index was significantly reduced in both ncRBD and cRBD groups compared to controls. When compared to the ncRBD group, A3 index was significantly decreased in the cRBD group. The Kaplan-Meier curve applied to cRBD estimated that a value of CAP rate below 32.9% was related to an average risk of conversion of 9.2 years after baseline polysomnography. Conclusion IRBD is not exclusively a rapid eye movement (REM) sleep parasomnia, as non-rapid eye movement (non-REM) sleep microstructure can also be affected by CAP changes. Further studies are necessary to confirm that a reduction of specific CAP metrics is a marker of neurodegeneration in IRBD.

Commonalities and Differences in NREM Parasomnias and Sleep-Related Epilepsy: Is There a Continuum Between the Two Conditions?

“…However, the numerous commonalities suggest that DoA and SHE share basic NREM sleep-related pathogenetic mechanisms. Accordingly, the high amounts of CAP rate found in both DoA and SHE patients are opposed to the reduced levels of CAP rate in REM sleep parasomnias (52).…”

Incidence and Progression of Rapid Eye Movement Behavior Disorder in Early Parkinson's Disease

“…Recent studies on the cyclic alternating pattern (CAP) have shown significant changes in CAP rates implying dysfunction of sleep regulatory mechanisms detectable in micro-sleep analysis before the macrostructure of sleep is altered, with a significant influence of disease duration on CAP rate in the course of the disease. 29,30 Two study limitations need to be mentioned. First, the relatively high loss of valid vPSGs during the study resulted in only 31 PD patients with RBD at some time point and valid vPSG data at every investigational time point.…”

“…The absence of RBD in the majority of de novo PD patients, as well as the failure to detect any significant difference in macro‐sleep structure based on conventional sleep staging, 9,29 implies that sleep pathology in PD does not follow an “all‐or‐nothing” principle but rather represents a gradual transition process. Recent studies on the cyclic alternating pattern (CAP) have shown significant changes in CAP rates implying dysfunction of sleep regulatory mechanisms detectable in micro‐sleep analysis before the macrostructure of sleep is altered, with a significant influence of disease duration on CAP rate in the course of the disease 29,30 …”

Case Report: Parasomnia Overlap Disorder Induced by Obstructive Sleep Hypopnea Apnea Syndrome: A Case Report and Literature Review

“…Obstructive sleep apnea hypopnea syndrome patients have increased CAP measures ( Korkmaz et al, 2018 ); therefore, they are more conditioned to suffer from nightmares and other parasomnias. Changes in the CAP, a biomarker of arousal instability in NREM sleep, are noted in NREM parasomnias ( Parrino et al, 2012 ) and some neurodegenerative diseases ( Melpignano et al, 2019 ).…”