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

Objectives: Rapid 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. Methods: Using 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. Results: The 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). Conclusion: The 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.