Retired 1st Sgt. Evan Childers recalled that as he became aware of changes in his cognition, he dismissed them as being part of aging.

The changes came on slowly, things like brain fog and memory lapses. “I would literally walk around with a notepad all day because that’s the only way I could remember stuff,” he said.

Childers, 39, retired from the U.S. Army in September 2024, having spent most of his 20-year career as a master breacher in the 75th Ranger Regiment after an early assignment as a mortarman with the 10th Mountain Division. He logged several deployments to the Middle East, “some of which were kinetic, some of which weren’t,” he said, adding that no matter what sort of deployment it was, “you were still training, and then obviously you had your training back at home station with heavy weapons, the Carl Gustaf [84 mm recoilless rifle] and more breaches.”

Diagnosed with mild traumatic brain injury, what he now knows is that his brain tissue accumulated little tears from repeated, close-proximity exposure to blast overpressure, an abnormally heavy pressure wave created by blasts or gunfire.

Slow Onset

Though he said he’d been exposed to large explosions, the symptoms of traumatic brain injury were slow to appear. He suggested that, because of the types of activities that come with soldiering, many people in the Army could be accumulating brain tissue tears, as he did. “I’ve had those instances where I was either knocked unconscious or got a bloody nose, or like when you shoot the Carl G, it can cause you to urinate blood after shooting too many rounds,” Childers said. “But over a soldier’s career, almost probably regardless of job, in some form or fashion, everyone is getting some form of blast overpressure.”

Labeled in medical journals as “the signature injury” of the fighting in Iraq and Afghanistan, traumatic brain injury (TBI) was diagnosed between 2000 and 2024 in close to 300,000 soldiers in the Regular Army, Army National Guard and U.S. Army Reserve, according to data compiled by the Defense Health Agency. The vast majority of those, 240,783, were classified as “mild” TBI, as Childers was.

To mitigate the effects of blast overpressure in future generations of service members, and to set the stage for early intervention of TBI, a DoD policy directive published on Aug. 8, 2024, requires, among other things, baseline cognitive assessments for new recruits and officer candidates in ROTC programs and the service academies.

The policy also requires acceleration of already mandated cognitive assessments for currently serving, high-risk, active-duty service members by the end of fiscal 2025, with the same test for all remaining service members “as soon as possible.”

Baseline cognitive assessments for new soldiers began in June 2024 with cadets attending summer training at Fort Knox, Kentucky, and continued through September at basic training sites at Fort Sill, Oklahoma; Fort Moore, Georgia; Fort Leonard Wood, Missouri; and Fort Jackson, South Carolina, said Col. Jama VanHorne-Sealy, director of the Occupational Health Directorate in the Office of the Army Surgeon General. Cadets at the U.S. Military Academy at West Point, New York, took baseline cognitive assessments in November, with seniors taking the assessment first because they were closest to entering the force, she said.

As long as these soldiers are in the Army, they will be reassessed every three years, with soldiers in high-risk jobs taking the assessment annually, VanHorne-Sealy said. “By the end of September 2027, every soldier of all ranks will undergo a baseline assessment, making soldiers who are entering the Army now the first generation to have their brain health tracked throughout their entire military career,” she said.

As proponent for the DoD directive’s implementation, the Army is working with the other services to conduct testing programs, she said. The intent of the assessments is to capture changes early, before a soldier is even aware of any changes.

Injury Symptoms

The primary criterion for diagnosing mild TBI is an altered state of consciousness, such as the temporary daze and confusion that comes from a whack to the head. There may be some memory lapses, but it “has to be less than 24 hours,” said Steven Porter, chief of the Neurocognitive Assessment Branch in the Army surgeon general’s office. “There are typical symptoms, dizziness, nausea, vomiting. Those can all be symptoms of concussive injury,” he said.

Recovery from mild TBI involves basic recovery strategies, said VanHorne-Sealy, who explained that “your brain will spontaneously recover if given the time to take a knee.” Moving away from the field environment where a soldier could be reinjured is key, as are things like avoiding televisions or computers. “Lots of blue light to the brain slows down recovery,” she said.

Moderate or severe cases of TBI are more dangerous, with symptoms such as brain bleeds, unconsciousness that lasts more than 24 hours, slurred speech and other physiological changes. “Moderate to severe TBI usually require significant medical intervention, because at that point, those are much more severe injuries that really surpass the capabilities of this instrument we’re using” for the baseline cognitive assessments, Porter said.

“It’s important to note that the neuropsychological tool that’s being used for the baseline assessments can identify cognitive changes even before the service member sees them in themselves, so early intervention is key for rapid recovery,” he said.

Laptop Test

Administration of a cognitive assessment may conjure images of a scientist in a white lab coat attaching electrodes to a soldier’s head under bright lights, but this test is simpler than that. “It’s a computerized neurocognition assessment instrument,” Porter said. “You open up a laptop, and it has different modules.”

Each of the program’s 10 modules contains a series of tests that assess different areas of the brain for things like reaction time to visual stimuli, spatial memory and cognitive processing, Porter said.

For example, in the first module, a soldier is instructed to click on a star as soon as it appears on the screen. The next test prompts the soldier to click on a pattern of numbers. “You have to visually see it, process what it is and then process a decision, left or right, left or right, and as the tests continue, they get more complex,” Porter said.

For example, a more complex test to assess spatial memory presents a design the soldier must memorize before it disappears. Within 10 seconds, a set of two designs will appear, and the soldier must identify the original design.

Because the assessment is delivered in modules, Porter said, it will help a provider pinpoint change in specific sections of the brain and whether there may be cause for concern. The assessment takes about 30 minutes to complete, is strictly visual—there is no auditory aspect—and can be done individually or in a group setting. It is not a pass-fail assessment. Rather, it is to establish a picture that is unique to each soldier’s cognitive abilities.

Combat Baselines

Cognitive assessments in the Army are not new. In late 2007, such testing became a step in the pre-deployment process for soldiers headed to the U.S. Central Command area of operations, and the results formed part of a database that could be referenced if needed. “In that time frame, we had a lot of IEDs, and there was a lot of concern that we wanted to know what your baseline was before you entered the combat environment,” VanHorne-Sealy said. “If something had happened, we had a baseline to compare you to.”

By comparison, the new cognitive assessments will be a starting point used to monitor a soldier’s brain health over a career.

The decision to begin baseline assessments of the youngest soldiers and officers is spelled out in the DoD directive addressing “practical risk management actions to mitigate and track blast overpressure exposures across the DoD.”

“Experiences by DoD personnel in training and operational environments demonstrate possible adverse effects on brain health and cognitive performance … resulting from acute … and chronic exposure to [blast overpressure],” the directive states.

Among the symptoms listed in the directive are headache, decreased reaction time, difficulty paying attention and memory loss from single or short-term, repetitive or continuous exposure to blast overpressure.

Weapons systems associated with blast overpressure include breaching explosives such as TNT, shoulder-mounted anti-tank and antipersonnel weapons such as the AT4, .50-caliber guns and rifles such as the M107 sniper rifle, and indirect fire systems such as howitzers and mortars.

The high-risk MOSs listed in the directive include field artillery, cannon crew member, infantry, combat engineer, cavalry scout, military police special reaction team, chemical corps, special operations forces and explosive ordnance soldiers.

Among other things addressed in the directive, exposure to blast overpressure should be minimized with adequate standoff distances during training, including for instructors, range safety officers and non-training audiences.

Under Pressure

The Army has been assessing blast overpressure for decades, VanHorne-Sealy said, by looking at ways to redirect weapons systems pressure away from the operator, “and we’re looking at the weapons systems themselves. There are some where minor changes can be made within a weapon system to decrease the pressure without altering the lethality of the weapon.”

Childers is now a subject-matter expert with InVeris, the company behind several firearms training simulators used by the Army. The simulators have been modified with solutions to lessen blast overpressure, he said. “Nothing’s going to take away from real-life training,” he said, but with simulators that mitigate danger to the brain, “you can get that muscle memory of the actions that need to take place before you go into a training environment.”

The new baseline cognitive assessments, he said, may help the Army get ahead of potential brain damage. Over his career in special operations, Childers said he witnessed a “pivotal moment” in which leaders, recognizing the effects of war, made Rangers take a knee for a bit. “Rangers are a bunch of very tough men, and we are also lucky enough to have a lot of smart guys,” Childers said. “From a cultural standpoint, we’re always going to get the job done, but I do think that we also have gotten better at taking care of ourselves.”