Photo By Sidney Hinds | SILVER SPRING, Md. (June 2, 2025) Rachel Barkey and Rania Abutarboush, with Naval...... read more read more
Brain injury poses a serious health threat to U.S. service members across the world. Cognitive impairment resulting from brain injury can negatively impact individual health, unit readiness and the lethal capacity of the nation’s forces.
In defense of U.S. service members, Navy Medicine Research & Development (NMR&D) has explored causes of and solutions to warfighter brain injury resulting from exposure to blast overpressure (BOP) for over 20 years, seeking answers to how injuries occur, and what measures can be taken to reduce the adverse effects of BOP on military readiness.
NMR&D scientists have taken on a range of challenges in the brain injury arena in the past two decades. Military operators use a variety of research-informed measures to minimize the potential adverse effects of blast exposure. Approaches include the use of protective gear, and techniques such as stand-off distances from explosives and weapons to minimize adverse effects.
Researchers with Naval Medical Research Command (NMRC), the headquarters of NMR&D, maintain multiple ongoing efforts and collaborations with partners across the medical science community to find solutions for U.S. service members.
Frequency
A recent NMRC study, executed in partnership with the University of Virginia (UVA), looked at service members (specifically, special operations personnel) who experienced large numbers of blast exposures over the course of their careers. The study explored a key factor of blast exposure that, despite brain injury being at the forefront of many national conversations, often gets left out: Frequency.
Stephen Ahlers, director of NMRC’s Operational Undersea Medicine Directorate (OUMD), emphasized that the total number and severity of blasts exposures are key factors in predicting future issues with brain inflammation and associated neurological effects.
Inflammation has been associated with reduced volume and thickness of brain structures, which can affect several key brain functions.
“It is well established that exposure to BOP events can result in traumatic brain injuries that range from mild to severe,” Ahlers explained, “but there has also been a concern that repetitive exposures to ‘low intensity’ BOP events that do not result in acute symptoms can contribute to a more subtle form of brain injury resulting from the accumulated effects of repetitive blast exposures, leading to impaired performance and mental decline.”
Very often these types of exposures are referred to as “subclinical,” since they do not result in acute symptoms.
One NMRC study examined data collected from breaching trainers: individuals exposed to many blasts over the course of two weeks in training to learn breaching techniques. Despite being physically located further away from explosions than the trainees themselves, breacher instructors, who had experienced many more blast exposures over potentially decades-long careers, showed neurological effects such as reduced cortical volume, alterations in the brain’s white matter axonal pathways and increased brain inflammation
NMRC researchers have been studying the effects of repeated low-level BOP exposure in military and veteran populations since 2006, alongside the command’s partner institutions.
(Here, ‘low-level’ refers to exposures that are experienced in the course of military duties with weapon systems and explosives, but do not result in an acute symptoms like a concussion.)
“Research performed by our colleagues at the Naval Health Research Center (NHRC) established that, in military personnel with a significant blast history, TBI outcome will be worse,” explained Ahlers. “A history of blast exposure that increases inflammation of the brain could explain why a history of BOP exposure can worsen TBI outcomes.”
Tracking
Efforts like those of NMR&D require a large body of research that scientists can draw from to inform their findings.
This information collection is critical to research in any field. The proper accumulation and organization of the data that research provides is what allows scientists to form conclusions, and allows policy makers to shape regulations in the interest of service members.
The challenge of accumulating data on individuals’ blast exposure history becomes even more difficult when it comes to brain injury, due to several factors, including weighing down the warfighter with measuring equipment, such as wearable blast dosimeters and the infrastructure required to capture data.
To address these complications, NMRC researchers developed the blast exposure threshold survey (BETS) to gauge the total amount of blast exposure individual military personnel had experienced over the course of their careers (generalized blast exposure value (GBEV), and determine how this history affects the brain.
The BETS is a self-reporting survey that asks service members to provide information on their exposure to munitions, in the context of their military careers, previous professions (such as law enforcement) and in their personal lives.
NMRC researchers are currently working alongside investigators from multiple institutions that use the BETS and GBEV to assess the health effects from blast exposure in military and veteran populations. Combined with the analytics capabilities of the command’s partners at UVA, this study will allow NMRC to update the GBEV algorithm using the collective responses and comprehensive health data collected by collaborators.
“It allows us to track certain key metrics,” Ahlers explained. “What categories of weapons systems are you exposed to? How often? How long since? Are you reporting any symptoms? Headaches? Slow thinking? It also helps us to establish a relationship between blast history and brain health effects.”
“This questionnaire is short,” added Dr. Hans Linsenbardt, a research psychologist with NMRC. “It can be given to thousands of people at a time, and it gives actionable information, whether that’s to researchers, the service members’ clinicians or whoever.”
Researchers use BETS results to create an individual’s GBEV. This value can be compared to known thresholds at which people begin to self-report symptoms of brain injury, and potentially mitigate exposure that could compromise warfighter health and performance.
Findings
“We have come to understand that all blast is not equal,” Linsenbardt remarked, when speaking to results from data gathered from the BETS tool. “Different weapon systems and different explosives have different effects on the brain. If you work a lot with artillery, for example, versus breaching explosives, you may see different neurological impacts.”
“Hearing changes are the canary in the coal mine when it comes to symptoms associated with repetitive blast exposures,” Ahlers added. “The tympanic membrane is the most sensitive to pressure, even when protected. Many career breachers report hearing issues later in their career, and when your hearing is impaired, you are more likely to have cognitive issues or even mental health concerns, such as PTSD.”
Data compiled by the BETS tool will empower military leaders to recognize when service members are approaching a number of exposures correlated with symptoms of brain injury, allowing necessary training for warfighters to take place without placing them at undue risk. Researchers are also identifying gaps in data collection that might represent additional factors in how brain injury will affect service members, to include factors such as diet and childhood history (such as participation in youth impact sports).
“We are incorporating key members of the DoD public health community, including representatives from the services and the Defense Health Agency, into this effort,” said Ahlers. “By integrating all of these components, we aim to enhance the support for the warfighter, operational units, DoD public health entities, and both DoD and VA health providers working to monitor and mitigate the effects of blast exposure on warfighter and veteran health and performance.”
This new study will draw upon 1,600 respondents to the BETS.
Blood and the Brain
As part of its research into brain inflammation, NMRC evaluates protein samples from brains to see how they are affected by different degrees of blast exposure.
These efforts look at blast effects on the body’s cerebrovascular system, or the network of vessels that provide blood to the brain. Damage to this network can impair cognitive function, and worsen outcomes for service members exposed to subsequent traumatic injury.
NMRC’s cerebrovascular research efforts have their origins in the command’s interactions with neurosurgeons treating blast-exposed TBI patients at Walter Reed in the early 2000s. Many of these patients had latent delayed cerebral vasospasm, a significant contraction of blood vessels that can reduce blood flow to the brain and that often occurs in otherwise uninjured parts of the brain.
NMRC was among the first groups to focus on cerebral vasculature as the system where brain injury might begin. Previously, most research focused on changes in the white matter of the brain (the neuronal axon bundles that conduct nervous impulses). According to NMRC researchers, changes in vasculature occur before changes in neurons, and lead to changes in blood and oxygen supply to the brain, which can in turn cause injury to or disease of the brain.
This holds true in other diseases of the brain, such as Parkinson's and Alzheimer's. The NMRC team has discovered that examining cerebrovascular disease is important to blast-related traumatic brain injury.
NMRC researchers were able to demonstrate that the mechanisms that lead to vasospasm occurred in the cerebral vasculature - the muscle cells in blood vessels and other support cells in the brain around blood vessels – and identify changes in those cells that led to poor oxygen flow to the brain.
This disruption of blood, and therefore oxygen, flow may cause, in the long run, neurological and cognitive issues in patients.
NMRC’s inflammation research has helped characterize how injury changes the brain, and has identified targets that can be used for diagnosis and treatment of service members.
“These discoveries help describe the underlying mechanisms involved with blast exposure-related changes in the brain,” said Ahlers. “These discoveries help us understand the disease. They help us name the disease for what it is. And most importantly, with that greater understanding of what the injury is, we can better prevent and treat the disease by developing sensitive biomarkers that come from an understanding of the complex physiological and biochemical changes in the brain.”
NHRC Research
Naval Health Research Center (NHRC), another command within NMR&D, has several research efforts underway into brain injury causes and prevention, which aim to enhance service member performance. One such research study is looking into how cold exposure can impair cognitive functions, which can in turn affect performance in areas like marksmanship, critical for military operations. The data collected from this study will inform methods that monitor, predict and prevent declines in performance in extremely cold operational environments.
These research projects use virtual reality and specialized measurement tools to evaluate how factors like brain activity, eye movement metrics and coordination relate to concussion recovery and operational readiness.
“We are investigating how these metrics correlate with cognitive and motor performance, including shooting accuracy and response times under varying conditions,” explained Pinata Sessoms, with NHRC. “This research aims to enhance our understanding of recovery trajectories and improve return-to-duty readiness for service members."
NHRC also has a long-term project underway to identify neuro-markers (here meaning measurable indicators or qualities of a brain that researchers can use to evaluate the effect of outside factors on that brain) for mild traumatic brain injury (mTBI) and PTSD, and to answer long-standing questions on service member personalized rehabilitation protocols and return-to-duty decision making following clinical treatment.
TBI research has additional applications for other forms of injury.
"Brain function can be disrupted not only by direct trauma, but also from physical injuries,” said Sessoms, “such as anterior cruciate ligament (ACL) rupture. Our Bayesian ACL project is exploring how the brain adapts during recovery and how these changes relate to proprioceptive [referring to the brain’s ability to perceive the location and movement of parts of the body] integration and motor performance. Understanding these neural adaptations is key to improving rehabilitation strategies and ensuring service members return to peak physical readiness after ACL reconstruction surgery."
“NHRC research has also shown a relationship between TBI and musculoskeletal injury,” Sessoms added, “which highlights the importance of ensuring service members are fit to return-to-duty in order to prevent subsequent injuries.”
The Path Ahead
NMRC is currently recruiting for a study to understand long-term health effects of mTBI, and examine long-term physical and mental changes.
Symptoms such as chronic headaches or sleep disturbances can be long-lasting, and can begin months after the initial injury. This study will seek to better understand why some symptoms may last longer than others, and use that information to develop methods to help service members recover faster and avoid those long-lasting symptoms.
“Protecting the neurological health of our service members is critical not only for their long-term well-being, but also for sustaining the readiness and operational effectiveness of our nation’s forces. By combining advanced neuroimaging, biomarker analyses, and computational approaches at the University of Virginia School of Medicine with the Navy’s decades of operational research, we are building the knowledge base needed to recognize, monitor and ultimately mitigate the effects of repeated blast exposure. This partnership is helping us move from simply documenting the problem to developing actionable solutions that safeguard the brain health of those who defend our country.”
Research is, by its nature, a long-term yield. Ongoing projects to evaluate brain inflammation in military and veteran populations employ highly sophisticated laboratory techniques, neuropsychological assessments and computational and statistical models to address the many factors and complexities at play.
The results to date of NMRC’s long-standing efforts into brain injury represent outcomes that can be applied directly to service member fitness and warfighter lethality. Ahlers’ team is currently working with the Navy and Marine Corps Force Health Protection Command and U.S. Navy leadership to make the BETS tool available as a mobile app to service members across the DoD, to aid military members and their leaders to protect them from the effects of excessive blast exposure, and keep them healthy, fit and ready to defend the nation.
“To see this work being recognized for its unique contributions is very meaningful to our team,” Ahlers commented. “We’re grateful that this work can potentially influence policy and practice, and therapies. We never foresaw this interaction and partnership with our military public health colleagues, but we welcome it wholeheartedly, because at the end of the day, what we're doing together will benefit the warfighter.”
| Date Taken: | 09.25.2025 |
| Date Posted: | 09.25.2025 09:11 |
| Story ID: | 549254 |
| Location: | SILVER SPRING, MARYLAND, US |
| Web Views: | 57 |
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This work, Brainstorming: NMR&D Protects the Military Mind, by Sidney Hinds, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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