This is an interesting result but I think that the prevalence at 2 years of follow-up is near the maximum prevalence of RBD in PD (I can't imagine that it would be much more than 50%) in all PD patients. Video PSG makes the diagnosis more objective but only reduces bias, it does not get rid of it completely. I am also not sure about RBE (which is new to me)... and how reliable this is as prodromal RBD... only 18% developed RBD and longer follow is required...
Sleep. 2016 Jun 9. pii: sp-00086-16. [Epub ahead of print]
Sixel-Döring F, Zimmermann J, Wegener A, Mollenhauer B, Trenkwalder C.
To investigate the development of REM sleep behavior disorder (RBD) and REM sleep behavioral events (RBE) not yet fulfilling diagnostic criteria for RBD as markers for neurodegeneration in a cohort of Parkinson disease (PD) patients between their de novo baseline assessment and two-year follow-up in comparison to healthy controls (HC).
Clinically confirmed PD patients and HC with video-supported polysomnography (vPSG) data at baseline were re-investigated after two years. Diagnostic scoring for RBE and RBD was performed in both groups and related to baseline findings.
One hundred thirteen PD patients and 102 healthy controls (HC) were included in the study. Within two years, the overall occurrence of behaviors during REM sleep in PD patients increased from 50% to 63% (P = 0.02). RBD increased from 25% to 43% (P < 0.001). Eleven of 29 (38%) RBE positive PD patients and 10/56 (18%) patients with normal REM sleep at baseline converted to RBD. In HC, the occurrence of any REM behavior increased from 17% to 20% (n.s.). RBD increased from 2% to 4% (n.s.). One of 15 (7%) RBE positive HC and 1/85 (1%) HC with normal REM at baseline converted to RBD.
RBD increased significantly in PD patients from the de novo state to two-year follow-up. We propose RBE being named "prodromal RBD" as it may follow a continuous evolution in PD possibly similar to the spreading of Lewy bodies in PD patients. RBD itself was shown as a robust and stable marker of early PD.