PROJECT SUMMARY/ABSTRACT Sleep disruption and related daytime dysfunction are common in people with Parkinson’s disease (PD), affecting up to 80% of patients. Despite this known prevalence of sleep-wake disturbance, it is not well understood how dysfunctional sleep-wake rhythms may contribute to cognitive and neuropsychiatric symptoms in PD Dementia (PDD) and the closely related Dementia with Lewy Bodies (DLB). Many of the brain regions involved in regulating daily patterns of sleep-wake behavior are also the earliest to be affected by Lewy Body (LB) pathology, as well as by co-occurring Alzheimer’s disease (AD) pathology, in PD and DLB patients. This Administrative Supplement requests supplemental funding in order to investigate associations between disrupted patterns of sleep-wake behavior, AD co-pathology, and cognitive and neuropsychiatric progression in the context of Lewy body diseases. We will apply novel analysis techniques, such as functional principle component analysis, to newly acquired continuous 24-hour high-resolution actigraphy data to assess patterns of sleep-wake behavior in PD and DLB patients. Uniquely leveraging PET and CSF biomarkers of concomitant tau co-pathology from the parent grant, we will quantify patterns of sleep-wake behavior in patient with pure LB and mixed LB/AD pathologies. The Aims of this study are: (1) to determine associations of disrupted patterns of sleep-wake behavior with cognitive performance and with neuropsychiatric disturbances in PD and DLB., and (2) to relate sleep-wake behavior phenotypes to biomarkers of tau co-pathology (PET and CSF) in PD and DLB. The proposed studies are highly responsive to NOT-NS-21-040 “Administrative Supplements for Collaborative Activities to Promote Sleep/Circadian Research in ADRD” and its stated goal “to facilitate collaborative research to better understand the bi-directional relationship between chronic sleep disturbances/circadian disruption and AD/ADRD pathogenesis”. This supplement also represents a new collaborative effort between sleep researchers (Dr. Jamie Zeitzer) and PD/AD researchers from the parent grant (Drs. Poston and Andreasson), and a provides a unique opportunity to examine the role of sleep-wake rhythms in the progression of cognitive impairment and dementia related to pure LB and to mixed LB/AD pathology in patients with PD and DLB.