Sleep stability in isolated rapid eye movement sleep behavior disorder, Parkinson's disease, and dementia with Lewy bodies

Background: Non-REM sleep symptoms remain poorly understood in alpha-synucleinopathies. Aims: The aims of the study were to compare sleep stability and transitions, arousals, and sleep cycle structure between isolated rapid eye movement (REM) sleep behavior disorder (iRBD), Parkinson’s disease (PD), and dementia with Lewy Bodies (DLB). Materials and Methods: Sleep transition and stability measures were assessed in one-night video-polysomnography records. Transition measures were the number of shifts between Wake and REM, Wake and NREM, and REM and NREM. Stability measures were the number of passages within the same sleep stage. We assessed arousals, the number/duration of sleep cycles (defined as a sequence of any NREM stage to REM), and the duration of N3 and REM sleep in each cycle. These variables were compared between two sets of groups (PD vs. DLB vs. iRBD and RDB+ vs. RBD−). Results: We assessed 54 PD, 24 DLB, and 21 iRBD patients (54 RBD+, 22 RBD−). There were no significant differences regarding sleep stability measures. Arousal indices in N1 and N2 stages were significantly higher in PD compared with iRBD. 24% of the sample did not have any sleep cycle. PD had significantly fewer cycles than iRBD. Differences became non-significant when adjusting for medication. There was no effect of group or time of night in REM or N3 duration. There were no significant differences between RBD+ and RBD−. Discussion: There were no significant differences in stability/transition measures. Arousals and disturbance in sleep cycling were higher in PD, but the difference was no longer significant after adjusting for medication. Conclusion: Different alpha-synucleinopathies have a similar degree of non-REM sleep instability, but medication could worsen symptoms in PD.