Clinical markers of neurodegeneration in Chinese patients with idiopathic rapid eye movement sleep behavior disorder

• Idiopathic RBD demonstrates a heterogeneous functional impairment.
• Olfactory impairment is a common feature of nigrostriatal degeneration.
• Systolic blood pressure drop closely correlates to the decline of motor impairment.

ObjectiveIt is reported that neurodegenerative markers of Parkinson’s disease occur in patients with idiopathic rapid eye movement sleep behavior disorder (idiopathic RBD); however, it has been unknown in Chinese patients. This study aims to provide a detailed understanding of the clinical features of Chinese patients with idiopathic RBD.MethodsWe conducted a series of Parkinson related motor and non-motor assessments in 181 participants including 41 patients with idiopathic RBD, 35 Parkinson’s patients without RBD, 42 Parkinson’s patients with RBD, and 63 healthy controls. The RBD questionnaire −Hong Kong (RBDQ-HK) was used to confirm clinical RBD symptoms and evaluate the severity. Motor function including Unified Parkinson’s disease Rating Scale (UPDRS), alternative tap test, Purdue Pegboard test and Timed Up and Go test, and non-motor functions including olfaction, cognition, and autonomic function were assessed in each group.ResultsMotor assessments of UPDRS, Purdue Pegboard, and Timed Up and Go, and the systolic blood pressure (BP) drop in patients with idiopathic RBD were intermediate between controls and Parkinson’s patients. However, the alternative tap test and some non- motor functions including olfaction and orthostatic symptoms in idiopathic RBD were impaired as seriously as in Parkinson’s disease. No difference was found in urinary and bowel function between idiopathic RBD and controls. In idiopathic RBD, functional impairment was associated with age and the severity of RBD symptoms (p < 0.05). In addition, systolic BP drops closely correlated to motor function and bowel function (p < 0.05).ConclusionsChinese patients with idiopathic RBD demonstrated an extensive and heterogeneous functional impairment. The association between functional impairment and age and the severity of RBD symptoms needs to be determined in future studies.