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• Posted May 9, 2023

Multiple Head Injuries May Raise Alzheimer's Risk for Veterans

People who repeatedly suffer traumatic brain injuries (TBI) may be more apt to develop Alzheimer's disease, new research shows.

TBI can result from direct hits to the head or from indirect sources such as shockwaves from battlefield explosions.

The brains of otherwise healthy military personnel who were exposed to explosions were found to have an abnormal accumulation of amyloid-beta protein, which can lead to Alzheimer's and other neurological diseases. The findings were published May 9 in Radiology, a journal of the Radiological Society of North America.

"Amyloid-beta is a molecule not normally found in the brains of young patients,"said study author Dr. Carlos Leiva-Salinas, associate professor of radiology at the University of Missouri School of Medicine. "Amyloid-beta accumulation in the brain is proposed to be an early event in the pathogenesis of Alzheimer's disease, the most common type of dementia worldwide, impacting millions of people."

Autopsy studies have shown the presence of amyloid plaques within hours of a severe brain injury. Certain forms of amyloid-beta can accumulate into tangles and plaques in the brain. This can lead to mental decline and neurodegenerative diseases.

"Noninvasive positron emission tomography, or PET, imaging could be used to identify early-stage amyloid-beta accumulation in individuals or professions exposed to traumatic brain injury such as military personnel, police officers, firefighters, football players, etc.,"Leiva-Salinas said in a journal news release.

The study included nine military grenade or breacher instructors at Fort Leonard Wood Military Base in Missouri from January 2020 to December 2021. They train recruits to use hand grenades, explosives and other mechanical methods to force open doors.

A healthy control group of nine civilians also participated.

All were men in their early 30s, a stage of life when amyloid buildup in the brain is not expected. They had no previous history of concussion.

Researchers evaluated each person twice, at the start and after blast exposure about five months later.

The military instructors logged the number of exposures to explosions, including the firing of weapons.

All participants had brain scans to look for amyloid changes. Researchers paid particular attention to six brain regions that are usually associated with Alzheimer's and TBI.

They found abnormal amyloid buildup in six of the nine participants who were exposed to explosions. Three had increased amyloid accumulating in one brain region; two participants had them in two regions, and one had three regions with abnormal accumulation.

None of the civilians had any abnormal amyloid accumulation.

"Further research needs to be done to establish the relationship between the frequency and the severity of traumatic brain injury and the degree of amyloid changes in the brain, the natural course of the observed accumulation, and other potential biologic risk factors for amyloid plaque deposition and the development of cognitive decline,"Leiva-Salinas said.

More information

The U.S. National Institutes of Health has more on traumatic brain injury.

SOURCE: Radiological Society of North America, news release, May 9, 2023