SLC6A3 and Parkinson disease: The aims of this study were (I) to compare prevalence and severity of clinical markers of prodromal synucleinopathy in RBD and control group, and (II) investigate whether these clinical markers, muscle activity during REM sleep, and the probability of prodromal PD according to MDS research criteria, are associated with dopamine transporter binding as a surrogate measure of SN degeneration.