The study “Association of Traumatic Brain Injury With Late-Life Neurodegenerative Conditions and Neuropathologic Findings,” published in JAMA Neurology, underscored that head injury did not seem to increase the risk for Alzheimer’s disease or other types of dementia, contradicting findings in earlier studies.
Given that 1.3 million Americans seek emergency care for head injury each year, any potential long-term effects of such injuries are likely to be substantial. To get a better grip of how people who suffered an earlier brain injury fare, Mount Sinai researchers, along with colleagues from the University of Washington School of Medicine, investigated records of 7,130 older adults — the largest study conducted on the topic.
Study participants were enrolled in three different studies that followed them to measure cognitive status and perform other clinical tests that could indicate the presence of neurodegenerative disease every one or two years.
Among them, 865 had suffered a traumatic brain injury with a loss of consciousness at some time point before study start; 142 had been unconscious for more than an hour. About 23 percent died during the study, which led researchers to seek links between head trauma and neurodegenerative disease via brain autopsies.
Among more than 7,000 participants, 1,537 developed some form of dementia, and another 1,322 developed Alzheimer’s disease, but the research team found no signs that head injury was more common in this group.
Head trauma could also not be linked to increased levels of amyloid-β plaque or accumulation of tau proteins inside neurons — features revealed at autopsy that characterize the Alzheimer’s brain.
In contrast, analyses showed that brain injury was much more common among the 117 Parkinson’s disease patients, and analyses showed that the presence of Lewy bodies — a hallmark of Parkinson’s disease in the form of α-synuclein aggregates in nerve cells — were significantly linked to traumatic brain injury with loss of consciousness less than an hour.
Researchers also noted that loss of consciousness for more than an hour increased the risk of microscopic strokes in the brain.
“The results of this study suggest that some individuals with a history of traumatic brain injury are at risk for late-life neurodegeneration but not Alzheimer’s disease,” said Kristen Dams-O’Connor, a co-author of the study and co-director of the Brain Injury Research Center and associate professor in the Department of Rehabilitative Medicine at Icahn School, in a news release.
Dams-O’Connor said researchers would rather identify and treat post-traumatic brain injury neurodegeneration while people are still alive, but to do that they need to first understand the disease.
“Prospective traumatic brain injury brain donation studies can help us characterize post-traumatic brain injury neurodegeneration, identify risk factors, and develop effective treatments,” she concluded.
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