• Posted March 14, 2024

Could War Zone Blasts Raise Veterans' Odds for Alzheimer's?

Combat veterans who suffered traumatic brain injuries due to explosive blasts may have markers in their spinal fluid similar to those of Alzheimer's disease, new research finds.

"Previous research has shown that moderate to severe traumatic brain injuries may increase a person's risk of Alzheimer's disease," said senior study author Dr. Elaine Peskind, of the VA Puget Sound Health Care System and the University of Washington School of Medicine. "What is lesser known is whether mild traumatic brain injuries from military training and combat may also increase a person's risk. Our study found that these concussions may indeed increase a person's risk of Alzheimer's disease."

Traumatic brain injury (TBI) is caused by a bump, blow or jolt to the head, an injury as in a motor vehicle crash, or in service personnel, blast and impact injuries. In a mild TBI, also known as a concussion, person may lose consciousness for up to 30 minutes.

The new study -- published online March 13 in the journal Neurology -- included 51 military veterans who suffered concussions from at least one war zone blast or a combination of blast and impact injuries. They were compared to 85 vets and civilians who had not experienced a TBI.

On average, those in the concussion group had experienced 20 blast concussions and two impact concussions. 

Participants took thinking and memory tests and had spinal taps to collect cerebrospinal fluid. Researchers measured levels of two biomarkers -- amyloid beta and tau -- that can be early indicators of Alzheimer's disease.

As those with a history of blast concussion aged, they had lower levels of two amyloid betas than the group without concussion, researchers found. Those were Aβ42 and Aβ40.

"A reduction in the levels of Aβ42 in the spinal fluid had been shown in other studies to be a marker of amyloid accumulation in the brain, reflecting one of the earliest steps in the development of Alzheimer's disease," Peskind explained in a journal news release. "The levels we saw in this study began at around 45, approximately 20 years earlier than is seen in the general population."

Researchers also linked lower levels of spinal fluid amyloid with poorer performance on memory and thinking tests. 

At age 50, on a test in which participants are asked to accurately connect a series of dots as fast as possible, those in the concussion group averaged 34 seconds longer than the group without concussions. 

And on a test that asked participants to recall words after a 20-minute delay, the average score for concussion group was 8.8 points, compared to 13.1 for those without concussion.

"Our data show that biomarkers in the spinal fluid associated with concussions from blasts share some properties with the processes that lead to Alzheimer's disease later in life," Peskind said. "While our research does not fully address whether veterans who experience these injuries will develop Alzheimer's disease, it raises the possibility that they may be on a pathway leading to dementia."

One limitation of the study: The group was young and had few participants over 45, an age well before Alzheimer's disease processes typically emerge. Researchers said longer, larger studies that incorporate brain scans to measure amyloid levels are needed.

The U.S. Department of Veterans Affairs and the University of Washington Friends of Alzheimer's Research funded the study.

More information

The U.S. Centers for Disease Control and Prevention has more about traumatic brain injury.

SOURCE: American Academy of Neurology, news release, March 13, 2024