Resting state electroencephalography alpha activity predicts cognitive scores in rapid eye movement sleep behavior disorder

Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is characterized by the loss of atonia during REM sleep, causing dream-enacting behavior. Although iRBD occurs without any clear signs of neurodegenerative disorders, most patients with iRBD eventually develop Parkinson’s disease or dementia with Lewy bodies, typically accompanied by cognitive decline. Hence, identifying a biomarker that reflects a neurophysiological state of iRBD has therapeutic potential. Here, we show that spatially clustered alpha (8–12 Hz) oscillatory activities in the scalp can predict cognitive performance in patients with iRBD. A cohort of 62 Korean patients with iRBD underwent resting-state electroencephalography (rsEEG) recordings and participated in the Montreal Cognitive Assessment tests, a common measure for cognitive function. Spectral analysis of the rsEEG data revealed that overall power and transient bursting parameters of alpha activity negatively correlated with Montreal Cognitive Assessment test scores. These results accounted for potential confounding factors such as the spatial distribution of the electrodes, age, sex, emotional states, and medication use. This finding was specific to the alpha activity because theta (4–8 Hz) and beta (12–30 Hz) oscillatory activities were not correlated with the cognitive test scores. Thus, these results suggest that clustered resting-state alpha activity is associated with cognitive impairments in iRBD. Our findings emphasize the importance of rsEEG dynamics in cognitive assessment and highlight the potential utility of rsEEG as an early biomarker for cognitive decline in iRBD patients.