REM Sleep Behavior Disorder in Parkinson's Disease: Change in Cognitive, Psychiatric, and Functional Outcomes from Baseline to 16-47-Month Follow-Up

Objective: Rapid Eye Movement Sleep Behavior Disorder (RBD) is common in Parkinson's Disease (PD) and is associated with cognitive impairment; however, the majority of the evidence on the impact of RBD on multidomain cognitive batteries in PD is cross-sectional. This study evaluated the longitudinal impact of probable RBD (pRBD) on cognitive, psychiatric, and functional outcomes in people with PD. Method: Case-control study. A total of 65 people with PD completed the study protocol at baseline and 16-to-47-month follow-up. Participants were classified as pRBD+ (n= 25) or pRBD- (n= 40) based on an established cutoff of 6 on the RBD Sleep Questionnaire (RBDSQ). Participants also completed a) comprehensive cognitive testing, b) self-report measures of depression, anxiety, and apathy, and c) performance-based and other-report forms of instrumental activities of daily living. Results: Baseline mean age was 67.8 (SD= 8.1; range= 45-86) and baseline mean years of education was 16.4 (SD= 2.1; range= 12-20). The two groups did not differ on measured demographic characteristics. Baseline mean T-scores for cognitive tests were in the average range (46-55). Hierarchical linear models tested group differences in cognitive and functional decline from baseline to follow-up, controlling for appropriate demographic and psychiatric variables. Compared to the pRBD- group, pRBD+ participants showed greater decline in attention/working memory (r=-0.31; p= 0.01) and UPSA financial skills (r=-0.31; p= 0.01). No other group differences approached significance. Conclusions: RBD may differentially affect attention/working memory and financial abilities in PD. Results underscore the importance of regular RBD screening in older adults with PD in order to triage symptomatic patients to appropriate cognitive and medical interventions.