Temporal distribution of electromyographic activity and behaviors in REM sleep in patients with isolated REM sleep behavior disorder

REM sleep behavior disorder (RBD) is characterized by excessive electromyographic (EMG) activity and abnormal behaviors in REM sleep. We aimed to examine the temporal distribution of EMG activity and behaviors in REM sleep in isolated RBD (IRBD) to better understand its nocturnal REM sleep circadian dynamics.

We examined the EMG activity in the mentalis and flexor digitorum superficialis muscles plus the clinical manifestations occurring in the first (from 11.00 p.m. to 3.00 a.m.) and last (from 3.01 a.m. to 7.00 a.m.) REM sleep episodes in the video-polysomnogram (V-PSG) of consecutive IRBD patients and controls without RBD.

We assessed the V-PSG of 45 IRBD patients and 39 matched controls. The last REM sleep episode showed higher EMG activity than the first in both patients (p = 0.010) and controls (p = 0.024). In patients, movements and vocalizations were more frequent and severe in the last REM sleep episode than in the first, but differences were not significant. In controls, the last REM sleep episode showed more simple minor movements (p = 0.026) of mild severity (p = 0.032) than the first. In both first and last REM sleep episodes, patients showed higher EMG activity (≥0.001) and more behaviors (≥0.001) than controls. REM sleep percentage, REM sleep duration, REM sleep latency and number of REM sleep episodes were similar between patients and controls.

When compared to the first REM sleep episode, the last REM sleep episode shows higher EMG activity and more frequent behaviors in both patients and controls, which are greater in patients than in controls. IRBD represents a pathological overrepresentation of the temporal physiological distribution of EMG activity and behaviors in REM sleep across the night.