Heart rate variability during sleep and the development of PTSD following traumatic injury

In the case of a life-threatening event, posttraumatic stress disorder (PTSD) may develop, causing the patient to experience panic and anxiety as well as social, occupational or other distresses. We look to investigate the role of sleep in the onset of PTSD and how it affects human autonomic functions. Specifically, this paper focuses on analysis of the heart rate variability in order to observe and quantify the activation of the sympathetic and parasympathetic nervous systems in both rapid eye movement (REM) sleep and non-REM (NREM) sleep. We hypothesize that the sympathetic activation is higher in those individuals whose PTSD symptoms continue in follow-up studies. Heart rate variability (HRV) signals, extracted from the electrocardiogram (ECG), were analyzed using autoregressive (AR) techniques to calculate the power spectral density (PSD), which in turn yield a low frequency to high frequency (LF/HF) ratio. This technique is established to be an index of autonomic nervous system activation. In addition to this ratio, we also looked at the roots of the AR function in order to obtain a more detailed depiction of the sympathetic activity. Our results suggest that the LF/HF ratio was higher in subjects with ongoing PTSD symptoms than those subjects without symptoms in both REM and NREM sleep. In the pole analysis, higher sympathetic nervous system activation was observed for PTSD positive subjects in REM sleep, but this sympathetic activity was slightly higher in PTSD negative individuals in NREM sleep.