1 SLEEPJ, 2021, 1–7 doi: 10.1093/sleep/zsab153 Advance Access Publication Date: 18 June 2021 Original Article Submitted: 29 January, 2021; Revised: 5 May, 2021 © The Author(s) 2021. Published by Oxford University Press on behalf of Sleep Research Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com Original Article Objective rapid eye movement sleep characteristics of recurrent isolated sleep paralysis: a case–control study Monika Kliková 1,2, * , , Marek Piorecký 1,3, , Eva Miletínová 1,2 , Karolina Janků 1,2 , Daniela Dudysová 1,2 and Jitka Bušková 1,2 1 National Institute of Mental Health, Klecany, Czech Republic, 2 Third Faculty of Medicine, Charles University, Prague, Czech Republic and 3 Faculty of Biomedical Engineering, Czech Technical University, Prague, Czech Republic *Corresponding author. Monika Kliková, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic. Email: monika.klikova@nudz. cz. Abstract Study Objectives: Recurrent isolated sleep paralysis (RISP) is a rapid eye movement (REM) parasomnia characterized by a dissociative state with characteristics of REM sleep and wakefulness. Pathophysiology has not yet been clarifed and very little research has been performed using objective polysomnographic measures with inconsistent results. The main aim of our study was to fnd whether higher REM sleep fragmentation is consistent with the theory of state dissociation or whether signs of dissociation can be detected by spectral analysis. Methods: A total of 19 participants in the RISP group and 19 age- and gender-matched participants in the control group underwent two consecutive full-night video-polysomnography recordings with 19-channel electroencephalography. Apart from sleep macrostructure, other REM sleep characteristics such as REM sleep arousal index, percentage of wakefulness and stage shifts within REM sleep period were analyzed, as well as power spectral analysis during REM sleep. Results: No difference was found in the macrostructural parameters of REM sleep (percentage of REM sleep and REM latency). Similarly, no signifcant difference was detected in REM sleep fragmentation (assessed by REM sleep arousal index, percentage of wakefulness and stage shifts within REM sleep). Power spectral analysis showed higher bifrontal beta activity in the RISP group during REM sleep. Conclusions: The results showed an underlying persistent trait of higher cortical activity that may predispose patients with sleep paralysis to be more likely to experience recurrent episodes, without any apparent macrostructural features including higher REM sleep fragmentation. Key words: polysomnography; recurrent isolated sleep paralysis; REM fragmentation; REM pathophysiology; REM sleep; REM sleep arousal index; power spectral analysis Statement of Signifcance We conducted the frst study to investigate objective rapid eye movement (REM) sleep characteristics (both macro- and microstructural) in participants with recurrent isolated sleep paralysis (RISP). We examined the characteristics of dissociation state during REM sleep outside of sleep paralysis (SP) episodes. We found no difference in the macrostructural parameters of REM sleep and no difference in REM sleep fragmentation. Power spectral analysis revealed higher bifrontal beta activity in the RISP group during REM sleep. Our results showed an underlying persistent trait of higher cortical activity that may predispose participants with SP to be more likely to experience recurrent episodes. Downloaded from https://academic.oup.com/sleep/article/44/11/zsab153/6305144 by guest on 11 January 2023