The timing between REM sleep behavior disorder and Parkinson's disease.

In Parkinson's disease (PD) patients, REM sleep behavior disorder (RBD) might precede PD or develop with or after the onset of PD. No previous study has explored differences between these two groups. The aim of this study was therefore to compare clinical features and REM sleep chin electromyographic patterns between patients in whom RBD heralded PD and those in whom RBD occurrence coincided with or followed the clinical manifestations of PD.Twenty-seven consecutive PD patients (mean age 67.9 years) were enrolled. Detailed clinical, laboratory, and polysomnographic studies were obtained in all participants.Sixteen of the 27 patients were affected by RBD. These had a significantly higher stage of PD and took significantly higher doses of dopaminergic therapy; their disease duration tended to be longer, and their cognitive status tended to be lower. PD patients in whom RBD preceded PD (n = 6) did not differ from PD patients without RBD in disease parameters, while PD patients in whom RBD developed with or after PD (n = 10) showed a significantly higher disease stage, took significantly higher dopaminergic therapy, and had a longer disease duration.Our findings are compatible with the hypothesis that patients in whom RBD precedes, or does not precede, PD might constitute two possibly distinct clinical and physiopathological groups, based on different progressive neuropathological sequences of events.