0877 Lower REM Parasympathetic Activity Accompanies PTSD Diagnosis and Greater Hyperarousal in Trauma-Exposed Individuals

Introduction Hyperarousal and abnormal autonomic functioning are core manifestations of posttraumatic stress disorder (PTSD). We examined associations of heart rate variability measures of parasympathetic activity during REM with PTSD diagnosis, self-reported hyperarousal and general psychopathology in recently traumatized individuals. Methods Individuals exposed to a PTSD Criterion-A trauma within the past 2 years (N=56, 35 females) aged 18-40 (mean 23.2, SD 4.6) underwent a night of ambulatory polysomnography (PSG) following an acclimation night. ECG recordings during REM-sleep periods of at least 5 min were analyzed using Kubios software. Each participant’s average Root Mean Square of the Successive Differences (RMSSD) and High Frequency (0.15-0.4Hz) power (HF) were calculated. Participants completed the Clinician-Administered PTSD Scale (CAPS-5, range 0-45, mean 20.1, SD 12.9) and the PTSD Checklist for DSM-5 (PCL-5). Twenty-three met DSM-IV-TR criteria for PTSD. Hyperarousal items from CAPS-5 and PCL-5 were combined into a Composite Hyperarousal Index (CHI). Likewise, a Composite Psychopathology Index (CPI) was created from the Symptom Checklist-90, the WHO Disability Assessment Schedule 2.0, and the Depression, Anxiety and Stress Scale. RMSSD and HF were compared between PTSD-diagnosed and non-diagnosed participants using unpaired t-tests. Their associations with CHI and CPI were analyzed with simple regression. Results Compared to non-diagnosed, trauma-exposed participants, those diagnosed with PTSD showed trends toward lower RMSSD [t(1,54)=1.893, p=0.064] and HF power [t(1,54)=1.987, p=0.052]. Across all participants, CHI correlated negatively with both RMSSD (R=-0.31, p=0.023) and HF (R=-0.28, p=0.035). These relationships were driven primarily by PCL-5 hyperarousal items which showed significant negative correlation with RMSSD (R=-0.365, p=0.006) and HF (R=-0.315, p=0.019), whereas CAPS-5 hyperarousal items did not reach significance (RMSSD:p= 0.13, HF:p=0.14). Total PTSD symptoms also predicted, but mostly as trends, RMSSD (CAPS-5:R=-0.231, p=0.09; PCL-5:R=-0.301, p=0.025) and HF (CAPS-5:R=-0.249, p=0.067; PCL-5:R=-0.258, p=0.057). CPI did not significantly predict either RMSSD (p=0.13) or HF (p=0.11). Conclusion PTSD diagnosis, greater self-reported hyperarousal and total PTSD symptomatology, but not general psychopathology, predicted decreased parasympathetic activity during REM. Decreased parasympathetic activity may lessen putative emotional