The Relationship Between Resting State Quantitative EEG and Daytime Sleepiness Complaints in Parkinson's Disease.

Although many studies have reported the presence of daytime sleepiness in Parkinson's disease (PD), either a weak or no association has been found between self-reported and current objective measures of daytime sleepiness in this population. Changes in resting state quantitative electroencephalography (qEEG) have been associated with increased subjective sleepiness induced by sleep deprivation in young and older adults. The aim of this study was to investigate the relationship between resting state qEEG and self-reported daytime sleepiness in adults with PD. Sixty-two participants with PD underwent polysomnographic recording and clinical assessment. Daytime sleepiness severity was measured with the Epworth Sleepiness Scale (ESS). Resting state EEG was recorded 30 min after awakening. Spectral power and functional connectivity analyses (weighted-phase lag index, amplitude-amplitude coupling) were performed on artefact-free resting state EEG in 2 Hz mini bands from 0.5 to 12 Hz. Partial correlations and a hierarchical regression were used to evaluate the relationship between the qEEG metrics and ESS scores. Lower phase synchronisation in the low alpha band (8-10 Hz) within the occipital cortex was the best EEG predictor of higher daytime sleepiness severity in PD. Our results are in line with some findings of previous studies conducted in healthy young participants that reported lower alpha connectivity after sleep deprivation, suggesting disrupted arousal networks may contribute to daytime sleepiness in PD. Lower alpha phase synchronisation within the occipital cortex could serve as a proxy for daytime sleepiness in PD.