Biomarkers of neurodegeneration in isolated and antidepressant-related rapid eye movement sleep behavior disorder

Background and purpose: This study compared the features of isolated rapid eye movement (REM) sleep behavior disorder (iRBD) and antidepressant-related REM sleep behaviour disorder (RBD) with the aim of highlighting markers that might distinguish the two entities. Methods: The observational cohort study included RBD patients with and without antidepressant use (antiD+ and antiD− patients, respectively), without cognitive impairment and parkinsonism. Clinical features of RBD, subtle motor and non-motor symptoms of parkinsonism, sleep architecture, REM atonia index, dopamine transporter-single photon emission computed tomography (DAT-SPECT) and skin biopsies for the intraneuronal alpha-synuclein (α-syn), were evaluated in the baseline work-up. Results: Thirty-nine patients, 10 antiD+ and 29 antiD−, were included. AntiD+ patients (more frequently female) reported more psychiatric symptoms, less violent dream enactment, and less frequent hyposmia. Dermal α-syn was detected in 93.1% of antiD− versus 30% of antiD+ patients (p = 0.00024). No differences appeared in other motor and non-motor symptoms, Movement Disorder Society–Unified Parkinson's Disease Rating Scale part III score, DAT-SPECT, or polysomnographic features. Conclusions: Patients with antidepressant-related RBD have clinical and neuropathological features suggesting a lower risk of evolution than those with iRBD.