Prospective outcome of rapid eye movement sleep behaviour disorder: psychiatric disorders as a potential early marker of Parkinson's disease

Increasing evidence suggests that rapid eye movement sleep behaviour disorder (RBD) is a heralding feature associated with evolving α-synucleinopathy-related neurodegenerative disorders.1–4 Several neurobiological markers such as olfactory abnormality were associated with the development of neurodegenerative disorders in ‘idiopathic’ RBD (iRBD) patients.5 On the other hand, pre-morbid psychiatric disorders were suggested as an important but often neglected preclinical marker of Parkinson's disease (PD),6 and its role is unclear in iRBD patients. The current study aimed to provide a quantitative risk estimate of neurodegenerative outcome, and to investigate the role of psychiatric disorders in predicting future neurodegenerative disorders in a prospective cohort of Hong Kong Chinese iRBD patients. Ninety-one iRBD patients (82.4% men) (recruited during 1994–2009) were prospectively followed-up with routine clinical assessments in our sleep centre for a mean duration of 5.6 years (SD 3.3).1 An additional research-based follow-up protocol has been implemented since 2008, which included neuropsychiatric examinations as conducted by the research …