Alterations of awake EEG in idiopathic REM sleep behavior disorder without cognitive impairment

•There are EEG changes at waking state in iRBD without cognitive impairment.•Higher absolute alpha power is found in the frontal region of iRBD compared to control.•Dominant occipital frequency is lower in iRBD than in controls. The aim of this study was to find electroencephalographic (EEG) changes in subjects with drug-naïve idiopathic rapid eye movement sleep behavior disorder (iRBD) who had no cognitive impairment. A total of 57 iRBD patients confirmed by polysomnography (PSG) and 33 sex and age-matched healthy controls were included and their waking EEG was recorded from five cortical regions for 15min. Power spectral analyses by fast Fourier transforms were performed on EEG data. In PSG data, the iRBD patients showed sleep disturbances of short total sleep time, decreased sleep efficiency, increased sleep latency and frequent awakening compared to controls. After adjusting for sleep parameters, the absolute alpha power in frontal region in iRBD patients was higher than that in controls (1.2±0.3 vs. 0.9±0.3, p=0.037). Dominant occipital frequency (DOF) was lower in iRBD patients than in controls after adjusting for the sleep covariates (9.2±0.3Hz vs. 9.5±0.4Hz, F=8, p=0.006). iRBD patients without cognitive impairment also showed EEG alteration in frontal and occipital cortex at wakefulness, which could be an early marker of cerebral dysfunction in iRBD patients.