Probabilistic sleep staging in MSLTs across hypersomnia disorders

Study Objectives: This study aimed to identify novel markers of narcolepsy type 1 (NT1) using between-nap opportunity periods (“lights on”) and in-nap opportunity periods (“lights off”) features of Multiple Sleep Latency Test (MSLT) recordings. We hypothesized that NT1 could be identified both from sleep–wake instability and patterns of sleepiness during wakefulness. Further, we explored if MSLTs from NT1 and narcolepsy type 2 (NT2) patients could be distinguished despite having the same diagnostic thresholds. Methods: We analyzed “lights on” and “lights off” periods of the MSLT, extracting 163 features describing sleepiness, microsleep, and sleep stage mixing using data from 177 patients with NT1, NT2, idiopathic hypersomnia (IH), and subjective hypersomnia (sH) from three sleep centers. These features were based on automated probabilistic sleep staging, also denoted as hypnodensities, using U-Sleep. Hypersomnias were differentiated using either or both features from “lights on” and “lights off.” Results: Patients with NT1 could be distinguished from NT2, IH, and sH using features solely from “lights on” periods with a sensitivity of 0.76 and specificity of 0.71. When using features from all periods of the MSLT, NT1 was distinguished from NT2 alone with a sensitivity of 0.77 and a specificity of 0.84. Conclusions: The findings of this study demonstrate microsleeps and sleep stage mixing as potential markers of sleep attacks and unstable sleep–wake states common in NT1. Further, NT1 and NT2 could be frequently distinguished using “lights off” features.