Plasma urate in REM sleep behavior disorder

Background: Rapid eye movement (REM) sleep behavior disorder (RBD) is associated with a high risk of developing Parkinson's disease (PD). Higher urate levels are associated with a lower risk of PD. We conducted a study to evaluate plasma urate levels in patients with RBD and their role in the development of PD. Methods: We evaluated plasma urate levels in a cohort of 24 patients with idiopathic RBD. Patients were divided into 2 groups according to the presence or absence of PD. Other known markers of the risk of developing PD, such as olfaction testing, and substantia nigra (SN) hyperechogenicity, were evaluated in the 2 groups. Results: No differences were observed regarding age, years of evolution of the RBD, SN hyperechogenicity, or plasma urate levels between the 2 groups. In patients without PD, there was a positive correlation between years of evolution of RBD and the levels of uric acid (R-2 = 0.88). Patients without PD and those who had more than 5 years of RBD exhibited higher levels of uric acid than patients with PD (P = 0.02). Conclusions: Higher levels of plasma urate were associated with a longer duration of RBD without converting to PD. Future prospective studies would be needed to confirm this finding. Disorder Society. (C) 2013 Movement Disorder Society