SUMMARY Traumatic brain injury (TBI) is a significant cause of death and disease in the armed forces, and it has been estimated that 10-20% of returning Operation Iraqi Freedom/Operation Enduring Freedom (Afghanistan) Veterans have suffered a TBI, with many having symptoms suggestive of the residual effects of mild TBIs (mTBIs) not recognized prior to discharge. In recognition of the latent residual effects of repeated exposures to blast, one of which may be mTBI, The 2020 National Defense Authorization Act includes a provision mandating documentation of blast exposure during both training and combat to inform future risk mitigation. The focus of the proposed study is to investigate the effects of exposures to blast and related symptomology incurred during operational training. In collaboration with DoD Walter Reed Army Institute of Research (WRAIR) investigators, we have obtained a critical mass of anonymized blood samples from military and law enforcement personnel from operational blast training courses, which will allow us to perform systematic DNA methylation and transcriptional studies. We have 2387 biological sample specimens along with demographic, symptom, and blast sensor data from both breaching and large caliber rifle protocols reflecting the exposures incurred by Veterans who because of their specific military occupational specialty (MOS) have repeated occupational overpressure exposure (ROPE), resulting in increased susceptibility to mTBI and associated symptoms. The overarching goal of this study is to link transcriptional regulatory perturbations associated with cumulative exposure to blast to chronic co-occurring physiological and psychological symptoms. Converging evidence in the field and from our own research has revealed molecular perturbations associated with ROPE. Specifically, we have shown blast associated alterations in DNA methylation (a highly stable epigenetic mark) in genes involved in sleep and circadian functioning, motivating our in-depth phenotyping of sleep disturbance in Veterans with ROPE in the proposed study. Here we will pursue the following aims: 1) Identify DNA methylation perturbations associated with cumulative occupational exposure to blast in ongoing cohorts; 2) Identify DNA methylation patterns that track with ROPE and associated physiological and psychological symptoms in ongoing cohorts; and 3) Identify altered DNA methylation patterns associated with cumulative blast in Veterans with MOS exposed to occupational blast newly recruited for this study. DNA methylation and transcriptional patterns in loci identified in the first 2 aims will be investigated in Veterans recruited with MOS involving varying durations and spectrum of exposures to occupational blast to determine whether these loci are also associated with cumulative blast and related clinical symptoms including sleep disturbance, with comorbid mTBI, PTSD and/or Major Depressive Disorder in these Veterans This will allow us to causally link blast-induced molecular changes via DNA methylation alterations that persist long-term in our Veterans who suffer from the chronic effects of blast. This study will lead to discovery of DNA methylation risk markers that may aid in identification of Veterans at risk before debilitating symptoms of ROPE can emerge, potentially allowing us to intervene clinically.

NARRATIVE It has been estimated that 10-20% of Veterans returning from Iraq and Afghanistan have suffered a traumatic brain injury, and many have symptoms suggestive of the residual effects of mild TBIs not recognized prior to discharge. Our study focuses on the latent effects of repeated exposure to blast during operational training. We will identify the associations among biological, physiological, and psychological symptoms in Veterans who, because of their specific military occupational specialty (MOS), have had repeated occupational overpressure exposure (ROPE) and whose symptoms may include sleep disturbances and comorbid PTSD, and/or Major Depressive Disorder.