Traumatic Brain Injury (TBI), a signature wound of Operations Enduring and Iraqi Freedom, can result from blunt head trauma or exposure to a blast/explosion. While TBI affects sleep, the neurobiological underpinnings between TBI and sleep are largely unknown. To examine the neurobiological underpinnings of this relationship in military veterans, [18F]-fluorodeoxyglucose positron emission tomography (FDG PET) was used to compare mTBI-related changes in relative cerebral metabolic rate of glucose (rCMRglc) during wakefulness, Rapid Eye Movement (REM) sleep, and non-REM (NREM) sleep, after adjusting for the effects of posttraumatic stress (PTS). Fourteen Veterans with a history of Blast Exposure and/or mTBI (B/mTBI) (age 27.5 ± 3.9) and eleven Veterans with no history (No B/mTBI) (age 27.7 ± 3.8) completed FDG PET studies during wakefulness, REM sleep, and NREM sleep. Whole-brain analyses were conducted using Statistical Parametric Mapping (SPM8). Between group comparisons revealed that B/mTBI was associated with significantly lower rCMRglc during wakefulness and REM sleep in the amygdala, hippocampus, parahippocampal gyrus, thalamus, insula, uncus, culmen, visual association cortices, and midline medial frontal cortices. These results suggest alterations in neurobiological networks during Wakefulness and REM sleep subsequent to B/mTBI exposure, may contribute to chronic sleep disturbances, and differ in individuals with acute symptoms.

Study Objectives: This study examined the extent to which self-reported exposure to blast during deployment to Iraq and Afghanistan affects subjective and objective sleep measures in service members and veterans with and without posttraumatic stress disorder (PTSD). Methods: Seventy-one medication-free service members and veterans (mean age = 29.47 ± 5.76 years old; 85% men) completed self-report sleep measures and overnight polysomnographic studies. Four multivariate analyses of variance (MANOVAs) were conducted to examine the impact of blast exposure and PTSD on subjective sleep measures, measures of sleep continuity, non-rapid eye movement (NREM) sleep parameters, and rapid eye movement (REM) sleep parameters. Results: There was no significant Blast × PTSD interaction on subjective sleep measures. Rather, PTSD had a main effect on insomnia severity, sleep quality, and disruptive nocturnal behaviors. There was no significant Blast × PTSD interaction, nor were there main effects of PTSD or Blast on measures of sleep continuity and NREM sleep. A significant PTSD × Blast interaction effect was found for REM fragmentation. Conclusions:The results suggest that, although persistent concussive symptoms following blast exposure are associated with sleep disturbances, selfreported blast exposure without concurrent symptoms does not appear to contribute to poor sleep quality, insomnia, and disruptive nocturnal disturbances beyond the effects of PTSD. Reduced REM sleep fragmentation may be a sensitive index of the synergetic effects of both psychological and physical insults. I NTRO DUCTI O NMild traumatic brain injury (mTBI) is one of the signature injuries of the Global War on Terror, and is among the leading factors contributing to disability and death among military service members of Operations Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF).1-4 mTBI is defined as a loss of consciousness lasting up to 30 minutes, alteration of consciousness/mental state from a moment up to 24 hours, and posttraumatic amnesia lasting 1 day or less, in the absence of detectable abnormal structural imaging findings.5 Between 30% and 40% of combat infantry and other military personnel who have served in OEF/OIF have been exposed to blast forces resulting from explosives, particularly improvised explosive devices (IEDs).6,7 While mTBI sustained from blast injuries are not the only means of sustaining mTBI (i.e., blunt trauma), blast injuries represent the most common type of mTBI reported in returning military personnel.3,8 Of those exposed to blasts, the reported prevalence rates of subsequent mTBI in warfighters vary between 4.9% to 22%. 6,7,9,10 The projected 2-year costs associated with chronic mTBI, which refers to symptoms and impairments that last more than three months post-injury, could average as much as $591 billion. 10Sleep disturbances are prevalent among both warfighters and civilians with subacute (i.e., < 3 months in duration) and chronic mild traumatic brain injury (cmTBI), and can impede recovery.11,12 As many...