Diagnostic Thresholds for Quantitative REM Sleep Phasic Burst Duration, Phasic and Tonic Muscle Activity, and REM Atonia Index in REM Sleep Behavior Disorder with and without Comorbid Obstructive Sleep Apnea

Objectives: We aimed to determine whether phasic burst duration and conventional REM sleep without atonia (RSWA) methods could accurately diagnose REM sleep behavior disorder (RBD) patients with comorbid OSA. Design: We visually analyzed RSWA phasic burst durations, phasic, ''any, and tonic muscle activity by 3-s mini-epochs, phasic activity by 30-s (AASM rules) epochs, and conducted automated REM atonia index (RAI) analysis. Group RSWA metrics were analyzed and regression models fit, with receiver operating characteristic (ROC) curves determining the best diagnostic cutoff thresholds for RBD. Both split- night and full-night polysomnographic studies were analyzed. Setting: N/A. Participants: Parkinson disease (PD)-RBD (n = 20) and matched controls with (n = 20) and without (n = 20) OSA. Interventions: N/A. Measurements and Results: All mean RSWA phasic burst durations and muscle activities were higher in PD-RBD patients than controls (P < 0.0001), and RSWA associations with PD-RBD remained significant when adjusting for age, gender, and REM AHI (P < 0.0001). RSWA muscle activity (phasic, any'' ) cutoffs for 3-s mini-epoch scorings were submentalis (SM) (15.5%, 21.6%), anterior tibialis (AT) (30.2%, 30.2%), and combined SM/AT (37.9%, 43.4%). Diagnostic cutoffs for 30-s epochs (AASM criteria) were SM 2.8%, AT 11.3%, and combined SM/AT 34.7%. Tonic muscle activity cutoff of 1.2% was 100% sensitive and specific, while RAI (SM) cutoff was 0.88. Phasic muscle burst duration cutoffs were: SM (0.65) and AT (0.79) seconds. Combining phasic burst durations with RSWA muscle activity improved sensitivity and specificity of RBD diagnosis. Conclusions: This study provides evidence for REM sleep without atonia diagnostic thresholds applicable in Parkinson disease-REM sleep behavior disorder (PD-RBD) patient populations with comorbid OSA that may be useful toward distinguishing PD-RBD in typical outpatient populations.