Associations Among Probable REM-sleep Behavior Disorder, Dopamine Transporter Binding, and Cognitive Performance in Parkinson Disease

BACKGROUND: While REM-sleep behavior disorder (RBD) is a robust prodromal marker of Parkinson disease (PD), little is known about the RBD's interaction with striatal dopamine transporter binding, a key neurobiological mechanism in PD. This study used a large-scale dataset of PD to examine the potential interaction between positive screening on probable RBD (pRBD) and striatal dopamine on cognition. METHODS: Sample included 1120 individuals (mean age 62.83±9.48, 38.0% female, 32.32% with pRBD) with PD. pRBD was screened using the RBD Screening Questionnaire. Dopamine transporter (DaT) single-photon emission computed tomography values were extracted for the putamen and the caudate. Cognitive performance was measured using neuropsychological tests. RESULTS: Regression analyses indicated that pRBD was significantly associated with the Symbol Digit Modalities Test (SDMT, B=-1.8, P =0.01), after adjusting for covariates. While there was no significant interaction between pRBD and striatal DaT measures on SDMT, pRBD's association with SDMT remained significant after adding DaT in the analytic model. CONCLUSION: In a large, early-stage PD cohort, a positive screen for probable RBD was significantly associated with a measure of processing speed and cognitive control. This association was not explained by dopamine transporter activity. Early screening of RBD would be important for treatment planning managing cognitive changes in PD.