A clinical research of rapid eye movement sleep without atonia in patients with narcolepsy

Abstract

Objective To quantitatively research the chin electromyography (EMG) increasing level of narcolepsy in rapid eye movement(REM) period, and analyze its association with clinical features and rapid eye movement sleep without atonia (RSWA). Methods Sixty-six patients with narcolepsy underwent video-polysomnography (video-PSG) and multiple sleep latency test (MSLT), and were grouped by quantitative research of the chin EMG levels during overnight REM (patients with elevated level belongs to RSWA group(n=31)). The data from general clinical data, video-PSG and MSLT and neuro-psychological assessment (Epworth Sleepiness Scale (ESS) and Montreal Cognitive Assessment) were analyzed statistically. Results Compared with narcolepsy without RSWA group (n=35), narcolepsy with RSWA group showed higher ESS score (17.9±4.1 vs 15.4±4.9, t=2.236, P=0.029), longer average time (min) per drowsiness (38.3±28.4 vs 19.2±11.2, t=2.931, P=0.030), higher incidence of cataplexy (58.1%(18/31) vs 28.6%(10/35); χ2=6.281, P=0.012). In the polysomnography parameters, narcolepsy with RSWA group had shorter sleep latency (2.00(0.50, 3.50) min vs 3.00(1.75, 9.50) min; Z=3.007, P=0.003), higher total arousal index (31.4±14.4 vs 22.9±13.1; t=2.368, P=0.021), and micro arousal index ((13.0±7.19)/h vs (9.2±6.5)/h; t=2.080, P=0.042) and spontaneous arousal index((11.9±7.1)/h vs(8.1±5.4)/h; t=2.500, P=0.015). There was no significant difference in sleep structure between the narcolepsy with RSWA group and narcolepsy without RSWA group. In MSLT parameters, shorter average REM sleep latency (min) appeared in narcolepsy with RSWA group(3.5±1.7 vs 5.3±4.5, t=-2.190, P=0.027). Logistic regression analysis showed that the phase of the chin EMG (OR=1.103, 95% CI 1.008-1.207, P=0.033) and tension chin EMG (OR=1.339, 95% CI 1.111-1.615, P=0.002)were significantly associated with cataplexy. Conclusions Narcolepsy with RSWA group showed sleep fragmentation, severer daytime sleepiness, and higher risk of cataplexy. Therefore, narcolepsy patients with high chin EMG had a higher prevalence of cataplexy. Key words: Narcolepsy; Electrophysiology; Polysomnography; Rapid eye movement sleep without atonia