Objective: To investigate REM density in patients with isolated REM sleep without atonia.

Background: Isolated RSWA (iRSWA) is regarded as a prodromal phase of REM sleep behavior disorder and subsequently of an underlying synucleinopathy (e.g. Parkinson’s disease) [1]. Defining a polysomnographic phenotype of iRSWA patients, with the focus on prodromal PD variables, is important for improving RSWA diagnosis. One of the polysomnographic variables is REM density: the number of Rapid Eye Movements per hour during REM sleep. REM density is typically decreased in PD [2] and increased in patients with major depression [3] and narcolepsy [4]. In this study, we have evaluated REM density in iRSWA patients.

Method: We compared REM density in 50 iRSWA patients with 40 control individuals. All subjects underwent a classic video polysomnography and a clinical assessment. RSWA and other sleep parameters were scored according to the AASM manual. REM density was calculated automatically (REM/hour). Differences between groups were calculated using a univariate GLM, adjusted for age and gender. Correlations between REM density and both phasic and tonic RSWA percentage were calculated with Pearson’s correlation coefficient, adjusted for age and gender.

Results: Mean REM density was 343.9 ± 112.5 in the iRSWA group and 266.5 ± 92.1 in the control group (p=0.001). Furthermore, we found a positive correlation between REM density and phasic RSWA (r=0.36, P=0.001) as well as tonic RSWA (r=0.23, P=0.032).

Conclusion: These findings suggest that an increase in RSWA is associated with an increase in REM density and both variables probably share an overlapping pathophysiology.

References: [1] B. Högl, A. Stefani, A. Videnovic. Idiopathic REM sleep behaviour disorder and neurodegeneration — an update.Nat Rev Neurol 14 (2018) 40–55. [2] L.A. Schroeder, O. Rufra, N. Sauvageot, F. Fays, V. Pieri, N.J. Diederich. Reduced Rapid Eye Movement Density in Parkinson Disease: A Polysomnography-Based Case-Control Study. Sleep 39 (2016) 2133–2139. [3] F.G. Foster, D.J. Kupfer, P. Coble, R.J. McPartland. Rapid eye movement sleep density. An objective indicator in severe medical-depressive syndromes. Arch Gen Psychiatry 33 (1976) 1119–1123. [4] J. Vanková, S. Nevsímalová, K. Sonka, N. Spacková, K. Svejdová-Blazejová. Increased REM density in narcolepsy-cataplexy and the polysymptomatic form of idiopathic hypersomnia. Sleep 24 (2001) 707–711.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rem-density-in-isolated-rem-sleep-without-atonia/