Characterization of Depressive and Anxiety Symptoms in Idiopathic REM Sleep Behavior Disorder

Background: Depression and anxiety are common in synucleinopathies and often present during prodromal stages, including idiopathic/isolated REM sleep behavior disorder (iRBD). However, the specific profiles of depression/anxiety and their predictive values for phenoconversion remain unclear. Objective: To assess the predominant manifestations, predictive value, and changes over time in depressive and anxiety symptoms in iRBD. Methods: Patients with polysomnography-confirmed iRBD (n = 114) and healthy controls (n = 44) were recruited. The Beck Depression Inventory and Beck Anxiety Inventory were administered at baseline, which was repeated prospectively over follow-up. Factor solutions were generated to delineate symptom clusters within the scales, and to help disentangle primary mood symptoms from other neurodegenerative confounds. Total scores, individual scale items, and factors were evaluated to 1) compare patients and controls, 2) assess progression of symptoms over time, and 3) assess predictive value for phenoconversion. Results: At baseline, iRBD patients had more severe depressive (9.0 = 6.7 vs 5.8 = 4.8) and anxiety (7.0 = 7.9 vs 4.5 = 6.0) symptoms than controls. Increased scores were seen in numerous individual scale items and most scales' factors. For depressive symptoms, there was no progression of total scores or factors over time. However, anxiety scores worsened slightly over prospective follow-up (annual slope = 0.58 points, p < 0.05). Over an average 2.4 = 3.1-year follow-up, 37 patients pheno-converted and 72 remained disease-free. Neither baseline depressive nor anxiety symptoms predicted phenoconversion to clinical neurodegenerative disease. Conclusion: Depressive and anxiety symptoms are common in iRBD. However, they do not predict phenoconversion and show only modest progression over time, solely for anxiety.