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Updated: Oct 26, 2026

Measuring Neural Mechanisms Underlying Sleep-Dependent Memory Consolidation During Naps in Early Childhood
Published on: October 2, 2019
Modified sleep stage sequence analysis based on the stage immediately preceding each REM sleep period during
Midori Mashita1, Hiroyoshi Adachi2, Yoshimasa Mamiya1
1Department of Psychiatry, Graduate School of Medicine, The University of Osaka, Suita, Japan; Sleep Medicine Center, The University of Osaka Hospital, Suita, Japan.
Objectives:
To evaluate whether a modified sleep stage sequence (SSS) method based on a single epoch immediately preceding each rapid eye movement (REM) sleep period during nocturnal polysomnography (nPSG) could help identify candidates for further narcolepsy workup.
Methods:
This study retrospectively analyzed 204 participants: 39 with narcolepsy type 1 (NT1), 63 with narcolepsy type 2 (NT2), 62 with idiopathic hypersomnia (IH), and 40 healthy controls (HC). In nPSG, REM periods were classified by the single 30-s epoch immediately preceding their onset, excluding sleep-onset REM periods (SOREMPs). The participant-level SSS(W/N1) ratio was the proportion of remaining REM periods preceded by wakefulness or N1. Decision trees distinguished NT1/NT2 from IH/HC using REM sleep latency (REML) alone or with this ratio, with 50 stratified 70/30 hold-out splits for internal validation.
Results:
In pooled multiple sleep latency test SOREMPs, the proposed method showed the same between-group ordering as conventional SSS. In pooled nocturnal REM periods excluding SOREMPs, the frequency of SSS(W/N1) was highest in NT1 and showed a stepwise numerical gradient across NT1, NT2, IH, and HC. Adding the SSS(W/N1) ratio to REML increased the median validation area under the receiver operating characteristic curve from 0.64 [interquartile range, 0.63-0.67] to 0.70 [0.68-0.74]. Two rounded high-specificity rules were derived: Rule A (REML-based), REML < 40 min; and Rule B (SSS-enhanced), SSS(W/N1) ratio ≥ 0.4 with REML < 125 min. Median sensitivity/specificity were 23%/98% and 37%/97%, respectively.
Conclusions:
A modified pre-REM SSS measure derived from routine nPSG may help prioritize patients for further narcolepsy workup.
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