Introduction Introduction: Rapid Eye Movement (REM) Sleep Behavior Disorder (RBD) is characterized by a lack of muscle atonia during REM sleep with dream enactment. RBD is regarded as a prodromal synucleinopathy as a high proportion of patients eventually phenoconvert to Parkinson's Disease and related synucleinopathies, suggesting RBD may be an early non-motor symptom of disease. Accordingly, patients with RBD are ideally situated to test potential therapeutic interventions to prevent

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... ersion to synucleinopathy. However, RBD itself, and associated patient registries, are rare. The North American Prodromal Synucleinopathy Consortium (NAPS) establishes a multisite registry of RBD patients with standardized neurological, neuropsychiatric, and neuropsychological assessments and biomarker collection. The present work reports baseline characteristics of this RBD patient database at its current state. Methods Methods: Participants >18 years of age with overnight polysomnogram-confirmed RBD by ICSD-3 criteria who did not meet criteria for the diagnosis of PD, dementia, MSA, or narcolepsy were enrolled from 10 sites across North America (8/2018 to 4/2021). Data collection included family and personal history of RBD and related symptoms, as well as standardized assessments related to cognitive, motor, sensory and autonomic function. Additionally, all subjects have contributed blood, and a subset of subjects have contributed cerebrospinal fluid samples to the National Centralized Repository for Alzheimer's Disease and Related Dementias for future analysis. Results Results: A total of n=251 participants were enrolled. Outcomes are reported based on sex (n=202 male, n=49 female). Data were further examined based on participants' history of antidepressant use (n=142 with, n=103 without) and based on participants' extent of synucleinopathy burden (n=70 defined as isolated RBD, n=181 defined as RBD+ [i.e., exhibiting ≥1 abnormality]). Any observed sex differences among the data did not persist after correction for antidepressant use. Conclusion Conclusions: This prospective, cross-sectional data on history, demographic, cognitive, motor, sensory, and autonomic function in n=251 participants with RBD highlight the lack of sex differences and the high preponderance of concomitant neurological abnormalities with RBD, and provide a valuable registry for future longitudinal studies and neuroprotective clinical trials. Support (If Any) NIH NIA R34 AG056639 (YJ, BB)