REM sleep behaviour disorder in Parkinson's disease is associated with specific motor features

Rapid eye movement (REM) sleep behaviour disorder (RBD) is commonly associated with Parkinson's disease (PD), and recent studies have suggested that RBD in PD is associated with increased cognitive impairment, waking EEG slowing, autonomic impairment and lower quality of life on mental health components. However, it is unclear whether the association of RBD in PD has implications for motor manifestations of the disease.

The study evaluated 36 patients with PD for the presence of RBD by polysomnography. Patients underwent an extensive evaluation on and off medication by a movement disorders specialist blinded to the polysomnography results. Measures of disease severity, quantitative motor indices, motor subtypes, complications of therapy and response to therapy were assessed and compared using regression analysis that adjusted for disease duration and age.

Patients with PD and RBD were less likely to be tremor predominant (14% vs 53%; p<0.02) and had a lower proportion of their Unified Parkinson Disease Rating Scale (UPDRS) score accounted for by tremor (8.2% vs 19.0%; p<0.01). An increased frequency of falls was noted among patients with RBD (38% vs 7%; p = 0.04). Patients with RBD demonstrated a lower amplitude response to their medication (UPDRS improvement 16.2% vs 34.8%; p = 0.049). Markers of overall disease severity, quantitative motor testing and motor complications did not differ between groups.

The presence of altered motor subtypes in PD with RBD suggests that patients with PD and RBD may have a different underlying pattern of neurodegeneration than PD patients without RBD.