Electroencephalographic Findings in Idiopathic Rapid Eye Movement Sleep Behavior Disorder with Objective Cognitive Impairment

Abstract

Background and Objective Patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) are at the risk of developing neurodegenerative disorders including mild cognitive impairment (MCI). MCI is prevalent among iRBD patients and is the predictive factor for future dementia. We hypothesized that objective cognitive impairment (OCI) might represent an even earlier phase of cognitive decline and demonstrate an association with early electroencephalographic (EEG) changes in iRBD patients. Methods A total of 263 patients with iRBD were divided into three groups according to their cognitive status that was assessed by neuropsychiatric test and structured interview: iRBD-normal cognition (NC), iRBD-OCI, and iRBD-MCI. Each of the participants underwent a waking quantitative EEG recording. Results iRBD-OCI showed better cognitive performance than iRBD-MCI, especially in the memory domain (p = 0.001). Group effect on EEG power was significant in theta (p = 0.043) and alpha range (p = 0.012). iRBD-MCI had higher theta (p = 0.005 and p = 0.012) and delta power (p = 0.005), and lower alpha power (all p < 0.01) compared to iRBD-NC. Although there was a trend of increasing slow-wave activity and decreasing alpha activity from iRBD-NC to iRBD-OCI to iRBD-MCI, the EEG power of iRBD-OCI did not significantly differ with either side. Conclusions iRBD patients with OCI may show early changes in EEG activity. Clinicians should recognize the clinical significance of OCI in the iRBD population and consider conducting neuropsychological tests even before the presence of the subjective experience of cognitive decline to detect the early stage of cerebral dysfunction and cognitive impairment.

Keywords

• rem sleep behavior disorder
• electroencephalography
• spectral analysis
• mild cognitive impairment
• synucleinopathies