Poor Test–Retest Stability of Nocturnal REM Sleep Onset Markers in Narcolepsy Type 1
Alexandre Derre, Claire Denis, Séverine Beziat, Isabelle Jaussent, Lucie Barateau, Yves DauvilliersAbstract
Study Objectives
To assess the test–retest stability of nocturnal sleep-onset REM periods (nSOREMPs) in untreated patients with narcolepsy type 1 (NT1), and of nocturnal direct REM (nDREM) transitions and their clinical and biological correlates
Methods
We included consecutive children and adults with NT1 diagnosed according to ICSD-3-TR criteria based on excessive daytime sleepiness, cataplexy, multiple sleep latency test (MSLT) findings, or CSF hypocretin-1 deficiency, without using nSOREMPs for diagnosis. All patients underwent two untreated overnight polysomnographic (PSG). nSOREMP was defined as REM sleep within 15 minutes of sleep onset, and nDREM as direct transition from wakefulness or N1 to REM sleep without intervening N2 or N3 sleep
Results
Among 227 patients (108 males; mean age 31.6 years (SD=14.8)), nSOREMPs were present on both PSGs in 41.8%, on one only in 35.7%, and absent on both in 22.4%, yielding poor test–retest agreement (κ=0.26, 95% CI 0.14–0.39, McNemar test p=0.10). Persistent nSOREMPs were associated with younger age, shorter sleep latency, more SOREMPs on the MSLT, and lower hypocretin levels, but not with PSG interval, symptom severity, or medication history. nDREM was present on both PSGs in 15.9%, on one PSG in 37.4%, and absent on both in 46.7%, with poor stability and persistence associated with younger age, shorter MSLT sleep latency, and lower CSF hypocretin levels.
Conclusions
nSOREMPs and nDREMs showed limited test–retest stability in untreated children and adults with NT1. Their association with age, MSLT findings, and hypocretin levels suggest variable REM dysregulation rather than stable individual traits. Absence of nSOREMP even on two PSG should not exclude NT1.