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Danielle Wasserman,1,2,* Dorothea Bindman,1,* Alexander D Nesbitt,1– 3 Diana Cash,4 Milan Milosevic,5 Paul T Francis,6 K Ray Chaudhuri,7 Guy D Leschziner,1,2 Luigi Ferini-Strambi,8 Clive Ballard,9 Amy Eccles,10 Ivana Rosenzweig1,2 1Sleep and Brain Plasticity Centre, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London, London, UK; 2Sleep Disorders Centre, Guy’s and St Thomas’ NHS Foundation Trust, London, UK; 3Headache Group, Department of Clinical Neurosciences, King’s College Hospital NHS Foundation Trust, London, UK; 4BRAIN, Department of Neuroimaging, King’s College London, London, UK; 5School of Public Health “Andrija Stampar“, University of Zagreb School of Medicine, Zagreb, Croatia; 6Wolfson Centre for Age-Related Diseases, King’s College London, London, UK; 7Movement Disorders Unit, King’s College Hospital, Department of Clinical and Basic Neurosciences, Institute of Psychiatry, Psychology & Neuroscience, Parkinson Foundation Centre of Excellence, King’s College London, London, UK; 8Sleep Disorders Center, Department of Clinical Neurosciences, Università Vita-Salute San Raffaele, Milan, Italy; 9Medical School, University of Exeter, Exeter, UK; 10Department of Nuclear Medicine, Guy’s and St. Thomas’ NHS Foundation Trust, London, UK*These authors contributed equally to this workCorrespondence: Ivana RosenzweigSleep and Brain Plasticity Centre, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London, Box 089, De Crespigny Park, London SE5 8AF, UKEmail ivana.1.rosenzweig@kcl.ac.ukIntroduction: Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is increasingly recognised as an important precursor disease state of alpha-synucleinopathies. This parasomnia is characterized by a history of recurrent nocturnal dream enactment behaviour, loss of skeletal muscle atonia, and increased phasic muscle activity during REM sleep. Neuroimaging studies of striatal dopamine transporter uptake tracer signaling suggest increasing dopaminergic deficit across the continuum of the alpha-synucleinopathies, with early sleep dysfunction suggestive of early caudate dysfunction. Henceforth, we set out to investigate the relationship between early sleep changes and the striatal dopaminergic availability in iRBD.Methods: Twelve patients with iRBD, who had undergone a video polysomnography and a neuroimaging assessment of striatal dopamine transporter (DaT) uptake tracer signaling, and 22 matched controls who had similarly undergone a video polysomnography were retrospectively identified. Data were statistically analyzed to identify altered sleep parameters and correlate them with striatal dopamine transporter uptake tracer signaling.Results: The iRBD patients exhibited an increased number of periodic limb movements during sleep (P=0.001), compared to 22 age-matched healthy subjects. In addition, several significant links were found between regional DaT-uptakes and sleep architecture. Correlational analyses suggested a strong positive association between sleep fragmentation and dopamine deficiency in left caudate (r=− 0.630, P=0.028), whilst an increased uptake in the whole striatum was strongly linked to the sleep efficiency, and to a lesser degree to the length of sleep duration.Discussion: To the best of our knowledge, this is the first demonstration of a close relationship between dopaminergic availability in striatum and the quality of sleep in iRBD. Taken together, our exploratory findings suggest that subtle but functionally significant striatal changes in early stages of iRBD may contribute to the further shaping of sleep architecture.Keywords: isolated rapid eye movement behaviour disorder, polysomnography, sleep architecture, striatum, striatal dopamine transporter uptake tracer signalling imaging, DaTSCAN