This analysis examines the clinical characteristics of the individuals with dopamine transporter (DAT) binding deficit in REM sleep behavior disorder (RBD) patients from the baseline assessment of the J-PPMI (The Japan Parkinson’s Progression Markers Initiative) study. 

In this J-PPMI study, 109 subjects were enrolled and evaluated DAT SPECT imaging, MIBG myocardial scintigraphy, physical examination, cognitive function screen, and questionnaire-based non-motor assessment at the baseline visit. We compared the clinical features of the group with DAT binding deficit with those without.

About half of the subjects showed decreased DAT binding in DAT SPECT imaging. In the DAT binding deficit group, MoCA-J (Montreal Cognitive Assessment for Japanese) and OSIT-J (odor stick identification test for Japanese) score was significantly low, and the heart-to-mediastinum ratio in MIBG scintigraphy was significantly reduced than those without. There was no difference between the two groups in the MDS-UPDRS score, Geriatric depression scale-15, State-Trait Anxiety Inventory, Epworth Sleep Scale, and SCOPA-AUT.

RBD patients with DAT binding deficit showed more advanced cardiac sympathetic dysfunction, olfactory disturbance, and cognitive decline than those without. It was considered that synuclein developed more extensively in the DAT binding deficit group, and that neuronal dysfunction due to synuclein accumulation was more severe.