Reduced striatal dopamine transmission in REM sleep behavior disorder comorbid with depression

Objective:To investigate dopamine transmission in patients with comorbid REM sleep behavior disorder (RBD) and major depressive disorder (MDD).Methods:This is a case-control study including 11 medicated patients with comorbid RBD and MDD (mean age 47.5 8.2), 8 medicated patients with MDD only (mean age 47.9 8.4), and 10 healthy participants (mean age 46.5 +/- 10.6 years). They underwent clinical assessment, video-polysomnography, olfactory tests, and neuroimaging studies (F-18-DOPA, C-11-raclopride, and F-18-FDG PET neuroimaging).Results:Compared with the 2 control groups, patients with comorbid RBD and MDD had significantly lower F-18-DOPA uptake at 60 minutes in the putamen and caudate after controlling for age and sex effect (p < 0.05). There were no significant differences for the C-11-raclopride and F-18-FDG-PET. The F-18-DOPA uptake in putamens had significant inverse correlation with severity of RBD symptoms (p < 0.01) and REM-related tonic muscle activity (p < 0.01). The comorbid RBD and MDD group had more impairment in olfactory function.Conclusion:Patients with comorbid RBD and MDD had presynaptic dopamine dysfunction and impaired olfactory function. There is a distinct possibility that the development of RBD symptoms among patients with MDD may represent an early phase of -synucleinopathy neurodegeneration instead of a merely antidepressant-induced condition.