Heart rate variability, sleep, and the early detection of post-traumatic stress disorder

\u3cp\u3eMeasures of heart rate variability (HRV) are sensitive indices of autonomic nervous system functioning, capable of distinguishing activity of its two constituent branches, the sympathetic and parasympathetic nervous systems. As such, these measures are possibly useful as early markers of post-traumatic stress disorder (PTSD). We review the anatomical and physiological background of the cardiovascular system and provide guidelines for measuring the electrocardiogram and for deriving HRV measures. In addition, normative values for various HRV measures are provided, both in the time domain and in the frequency domain. We then review literature linking these HRV measures to PTSD, to sleep, and to the combination of PTSD and sleep. From this review, it appears that during awake resting states, PTSD patients are characterized by low parasympathetic tone, relative to healthy controls, resulting in elevated mean heart rates and reduced cardiac reactivity. By contrast, during sleep PTSD patients appear to be characterized by increased sympathetic activation, mainly observed during REM sleep, again with elevated mean heart rate and reduced reactivity as a consequence. We advocate the use of HRV measures in studies aimed at identifying individuals at risk for developing PTSD symptoms.\u3c/p\u3