Differences in clinical characteristics when REM sleep behavior disorder precedes or comes after the onset of Parkinson's disease.

Abstract Objective Rapid eye movement (REM) sleep behavior disorder (RBD) is important not only as a preclinical symptom of Parkinson's disease (PD), but also as an aggravating symptom of PD. However, it is not known whether the onset of RBD in relation to PD affects the clinical characteristics of PD. A cross-sectional study comparing clinical characteristics of PD between patients with RBD occurring before and after the onset of PD was conducted. Methods Interviews regarding RBD symptoms were conducted and polysomnography was performed on 136 patients with PD. Patients with PD were divided into a group with RBD and a group without RBD. Moreover, the group with RBD was subdivided into those with RBD before the onset of PD (RBD → PD) and those with RBD after the onset of PD (PD → RBD). Clinical characteristics of the patients with and without RBD, and PD with RBD → PD and PD → RBD were compared. Results Patients with RBD (47 PD patients) had more severe parkinsonian symptoms, autonomic dysfunction, and cognitive impairment than those without RBD (89 PD patients). Moreover, 38 PD patients with PD → RBD had greater cognitive impairment including Mini-metal examination than 9 with RBD → PD in spite of similar motor and autonomic dysfunction with similar dopaminergic agents. Conclusion The occurrence of RBD after the onset of PD might be an important factor aggravating cognitive function.