Research suggests that moderate to severe TBI increases the risk of Alzheimer's disease. Whether the same is true for mTBI remains relatively unknown. In the present study, researchers investigated whether blast-related mTBI is linked to cerebrospinal indicators of Alzheimer's disease.
To do so, they analyzed cerebrospinal fluid samples from 51 US veterans of the wars in Afghanistan and Iraq. Each had suffered from mTBIs stemming from exposure to blasts, and had an average of 20 blast injuries. An mTBI was defined as a loss of consciousness for 30 minutes or less with no sign of brain damage on a standard clinical MRI or CT scan, and is considered as equivalent to a concussion. The researchers compared the results from exposed veterans with those from 85 veterans and civilians of a similar age with no history of TBI.
Ultimately, the researchers found that veterans in their late 40's and 50's had lower levels of beta-amyloid proteins compared to veterans and civilians who did not have the same injuries. Decreased levels of alpha-beta proteins in spinal fluid have been linked to Alzheimer's disease.
They further found that having lower beta-amyloid 42 levels was linked with poorer verbal memory and verbal fluency performance in cognitive tests among older veterans who had experienced mTBI.
"A decline in beta-amyloid 42 is the earliest detectable change due to Alzheimer's that can be found in a cognitively normal person," said senior author of the study, Dr. Elaine Peskind, Research Professor of Psychiatry at the University of Washington, in a press release.
"The change can appear as much as 20 years before symptoms. So a person can have the pathology of Alzheimer's going on in their brain but still not have any symptoms- no problem with their memory or thinking functions- for as long as 20 years," she added.
The researchers also found that veterans exposed to mTBI had abnormal levels of tau protein in their cerebrospinal fluid, suggesting that the normal brain clearance system may not have been working as well in people with mTBI.
The researchers wrote that their findings suggest chronic neuropathologic processes linked with blast mTBI share properties with processes linked to the onset of Alzheimer's disease. This, they continued, raises concerns that veterans with blast mTBI may develop a 'dementing disorder' later in life.
Sources: Neurology, Science Daily
