1174 Electrophysiological Correlates of Cognition in REM Sleep Behavior Disorder: Selective Sensitivity to Non-Memory Domains

Abstract Introduction Idiopathic REM sleep behavior disorder (iRBD) is a prodromal α-synucleinopathy often marked by cognitive decline. Quantitative EEG (QEEG) measures such as the theta/beta (TBR) and theta/alpha ratios (TAR) have been suggested as noninvasive markers of early neurodegenerative change. This study investigated whether longitudinal changes in TBR and TAR predict early cognitive decline in iRBD. Methods Patients diagnosed with iRBD by video-polysomnography between 2016 and 2018 were followed for an average of 6.4 years and underwent repeated neuropsychological testing and QEEG. Cognitive stability was defined by z-score changes in the CERAD-K battery. Longitudinal changes in TBR and TAR were compared between cognitively stable and declined groups, with additional analyses for memory and non-memory domains. Results Of 87 eligible patients, 55 were included in the final analysis. The mean age was 65.9 years, and were 37 were men. Group-by-visit interactions were not significant for the overall cognition or the memory-domain. In contrast, significant interactions emerged exclusively in the non-memory domain, with effects observed for TBR across all lobes (all p < 0.05), and for TAR in the frontal, temporal, parietal, and occipital regions (all p < 0.05). In the non-memory domain, cognitively stable patients exhibited modest TBR increases in temporal, central, and parietal regions and TAR increases in central region, whereas cognitively declined patients demonstrated marked increases in both TBR and TAR across all lobes. Conclusion TBR and TAR, relect longitudinal changes associated with non-memory cognitive decline in iRBD. These findings suggest that QEEG may serve as a promising biomarker for early neurodegenerative disease progression. Support (if any)