The inter-night variability of REM sleep without atonia in adult patients with central disorders of hypersomnolence.

STUDY

OBJECTIVES

Rapid eye movement (REM) sleep without atonia (RWA), the neurophysiological hallmark of REM sleep behavior disorder, is a typical feature of nocturnal sleep in patients with narcolepsy type 1 (NT1). Its reproducibility across different nocturnal polysomnographies (PSG) has never been investigated in patients with CDH. We assessed the inter-night variability of RWA.

METHODS

Two-hundred-fifty adults (45 % males) hospitalized for suspected CDH, including 92 NT1, 29 narcolepsy type 2 (NT2), 36 idiopathic hypersomnia (IH), and 93 subjective hypersomnolence (sHS), undergoing two consecutive night-PSGs, multiple sleep latency test (MSLT) and cerebrospinal fluid hypocretin-1 (CSF-HCRT1) measurement, were recruited. The inter-night variability of REM atonia index (RAI) was assessed with Wilkoxon's test, McNemar's test, Bland-Altman plots, and Cohen's kappa.

RESULTS

Compared with the other groups, NT1 patients presented lower RAI both as absolute values and frequency in the pathological range (RAI≤0.8). RAI slightly decreased from night1 to night2 only in NT1 (difference = 0.03, 95 %CI = 0.01-0.05), whereas it did not vary in other groups. In NT1, the frequency of pathological RAI≤0.8 was not different across the nights and showed good agreement (32.5 %vs.42.5 %; p = 0.09, kappa = 0.7). In NT1, after adjustment, RAI≤0.8 was independently associated with older age, lower MSLT sleep latency, more MSLT-sleep onset REM periods, higher wake after sleep onset, non-REM stage-1, and less non-REM stage-3.

CONCLUSIONS

In CDHs, RWA has low inter-night variability, which makes it a valuable marker in clinical practice and research activity. In adult NT1, RWA is associated with older age and with features suggestive of a poorer sleep quality and higher daytime sleep propensity.