Brief CommunicationInvestigating the night-to-night variability of REM without atonia in Parkinson's disease

- We examined the variability of rapid eye movement (REM) without atonia in Parkinson's disease.
- The measurement of REM without atonia was performed using the REM atonia index.
- REM without atonia was closely correlated across two nights of polysomnography.
- The REM atonia index demonstrated low variability over two nights of polysomnography.

ObjectivesRapid eye movement (REM) sleep behaviour disorder is frequently observed in Parkinson's disease and is characterized electrophysiologically by the absence of atonia during REM sleep. However, the night-to-night variability of REM sleep without atonia is yet to be determined in Parkinson's disease.MethodsUsing polysomnography, this study measured the variability of REM sleep without atonia across two consecutive nights, using the REM atonia index in 38 patients with Parkinson's disease.ResultsThe intraclass correlation coefficient between the REM sleep atonia index across two nights was 0.816 (F = 9.795, p < 0.001) and the difference between the two nights was 4.7% (standard deviation (SD) 8.2).ConclusionThe REM atonia index demonstrated low variability across two consecutive nights of PSG. Furthermore, the diagnosis of REM sleep behaviour disorder based on this electrophysiological marker and other clinical variables was in agreement across the two nights.