Posttraumatic stress disorder (PTSD) is linked to accelerated aging and is associated with increased risk of early-onset cardiovascular disease (CVD) in both men and women. The pathophysiological link between PTSD and CVD is complex and multi-factorial that likely involves premature vascular aging (i.e., large elastic arterial stiffening and vascular endothelial dysfunction) and autonomic dysfunction (e.g., reduced cardiovagal baroreflex sensitivity \[cBRS\] and heart rate variability \[HRV\]), along with other mechanisms. Vascular aging and autonomic dysfunction are key antecedents in the development of CVD and individuals with PTSD have greater arterial stiffening, endothelial dysfunction and reductions in cBRS and HRV compared to those without PTSD. The mechanisms by which PTSD contributes to greater vascular and autonomic dysfunction are not completely understood. Sleep is important for cellular and tissue repair, free radical detoxification and reducing oxidative stress and inflammation. Sleep disturbance is a hallmark symptom of PTSD and is associated with biomarkers of vascular aging, autonomic dysfunction and increased risk of CVD. Nightmares, a central feature of PTSD associated-sleep disturbance, are a debilitating symptom that can lead to insomnia or sleep deprivation, daytime sleepiness or fatigue, mood disturbances, cognitive impairments, behavioral problems, or other sequela, that ultimately causes clinically significant distress and impairment in social, occupational and physiological function, as well as increased CVD risk. As such, therapeutic strategies and interventions aimed at reducing nightmare-associated sleep disturbances in individuals with PTSD are clinically important for improving sleep quality, cardiovascular health and risk for future age-associated CVD.

Various psychotherapeutic (e.g., imagery rehearsal therapy \[IRT\]) and pharmacological (e.g., prazosin) interventions are available for treatment of nightmares associated with PTSD. However, the evidence for their efficacy for addressing sleep disturbances is inconsistent, particularly with pharmaceuticals, and implementation barriers and poor adherence exist with psychotherapy. As such, novel alternative approaches, including the use of digital medicine such as app-based and digital platforms are being developed to improve treatment delivery. NightWare™ digital therapeutic system is one such novel platform that was recently granted Breakthrough Device designation by the FDA for the treatment of nightmares in adults with PTSD. NightWare uses a proprietary application on the Apple Watch® to collect biometric data (i.e., heart rate \[HR\] and body movement) to learn sleep patterns to create a stress Index. When an individual exceeds this index due to entering a nightmare, NightWare intervenes by sending vibrotactile feedback to the Apple Watch, arousing the individual and interrupting the nightmare without waking or disrupting sleep. Through machine learning, NightWare continually refines its model and knowledge of the person's response, consequently leading to fewer nightmare associated awakenings. In unpublished preliminary studies, NightWare was shown to be safe (no change in suicide risk or daytime sleepiness) and a tendency to have greater improvement in objective measures of sleep quality (i.e., Pittsburgh Sleep Quality Index \[PSQI\] and amendment for PTSD \[PSQI-A\]) compared to sham (NightWare but intervention disabled, i.e., no vibration). Whether NightWare improves cardiovascular health in adults with PTSD-related nightmares has yet to be studied.

Accordingly, the investigators are proposing a randomized, double-blind, placebo (i.e., sham intervention) controlled parallel pilot study that will provide the first clinical evidence for the efficacy of the NightWare digital therapeutic system to improve cardiovascular health outcomes in adults with PTSD-related nightmares.