Occurrence and clinical correlates of REM sleep behaviour disorder in patients with Parkinson's disease over time

Objective: To examine the occurrence and clinical and demographic correlates of REM sleep behaviour disorder (RBD) in patients with Parkinson's disease (PD) in a community-based cohort over 8 years. Methods: 231 patients with PD were included in a population-based prevalence study in 1993. Patients were then followed prospectively and reexamined after 4 and 8 years. Semi-structured interviews for information on clinical and demographic data were applied at all study visits. Standardised rating scales of parkinsonism, depression and cognitive impairment were used. The diagnosis of probable RBD (pRBD) was based on a sleep questionnaire. Proportional-odds ordinal logistic regression models for clustered data were used to study the relationship between pRBD and various demographic and clinical variables. Results: 231 patients were evaluated for RBD in 1993 and, after 4 and 8 years, 142 and 89 patients, respectively, were available for re-evaluation. The frequency of pRBD varied from 14.6% to 27% during the study period. Probable RBD was related to male gender, higher dopaminergic treatment and less severe parkinsonism. Conclusion: We found that the frequency of pRBD varied over time and that it is associated with male gender, less parkinsonism and higher levodopa equivalent dose. Our findings indicate that dopaminergic therapy may contribute to the expression of RBD and that RBD is symptomatic in earlier stages of PD.