Prodromal Lewy body disorder features in REM sleep behavior disorder with biomarker-defined synucleinopathy

ABSTRACT Objective Isolated rapid eye movement sleep behavior disorder (iRBD) is a prodromal state for Lewy body disorders and exhibits biological heterogeneity that may influence clinical expression and progression. We examined clinical features in individuals with iRBD and biomarker-defined synucleinopathy. Methods Parkinson’s Progression Markers Initiative (PPMI) is a longitudinal, multi-center observational study. Participants included polysomnogram (PSG)-confirmed iRBD individuals who were cerebrospinal fluid (CSF) α-synuclein seed amplification assay positive with no clinical diagnosis of Parkinson’s disease or dementia with Lewy bodies, along with robust healthy controls (HCs). Clinical and biological features of prodromal PD and DLB, including mild cognitive impairment (MCI), subthreshold parkinsonism, and a range of neuropsychiatric, autonomic and sensory symptoms, were assessed. Results Compared with HCs ( N =136), iRBD participants ( N =197) demonstrated worse cognitive performance, including a lower cognitive summary score ( p