Traumatic brain injury (TBI) with a loss of consciousness (LOC) may be linked to later development of Parkinson’s disease but not Alzheimer’s disease, according to researchers at the Icahn School of Medicine at Mount Sinai and the University of Washington School of Medicine.
The new study contradicts findings from other high-profile studies showing a link between TBI and future Alzheimer’s disease.
With more than 1.3 million Americans visiting an emergency department each year with TBI, there is great interest in the long-term effects of these injuries and the widespread public health implications.
In the largest study to date on this subject, the researchers analyzed head injury data from 7,130 older adults. The research was part of three prospective studies that included annual or biennial cognitive and clinical testing.
Of this group, 865 people had suffered TBI with LOC at some point before the study began; 142 of these individuals had been unconscious for more than one hour. The researchers looked for any associations between TBI and late-life clinical outcomes, such as dementia, Alzheimer’s disease, mild cognitive impairment, Parkinson’s disease, and change in parkinsonian signs.
The findings showed a strong association between TBI with LOC greater than an hour and Parkinson’s disease (117 cases during the study).
No statistically significant link was found between TBI with LOC and dementia risk when the group with TBI with LOC was compared with the 1,537 patients who developed dementia during the study. Results for Alzheimer’s disease (diagnosed in 1,322 study participants) were similar.
Furthermore, based on 1,652 autopsy findings, no association was found between TBI with LOC and beta amyloid plaques or neurofibrillary tangles, the hallmark indicators of Alzheimer’s disease.
However, the autopsies did find an increased risk for Lewy bodies (abnormal aggregates of protein) in TBI with LOC less than an hour and an increased risk of cerebral microinfarcts (microscopic stroke) in TBI with LOC more than an hour.
“The results of this study suggest that some individuals with a history of TBI are at risk for late-life neurodegeneration but not Alzheimer’s disease,” said Kristen Dams-O’Connor, Ph.D., co-director of the Brain Injury Research Center and associate professor in the Department of Rehabilitative Medicine at the Icahn School of Medicine at Mount Sinai.
“We want to identify and treat post-TBI neurodegeneration while people are still alive, but to do this, we need to first understand the disease. Prospective TBI brain donation studies can help us characterize post-TBI neurodegeneration, identify risk factors, and develop effective treatments,” she said.
The findings also suggest that clinicians may be misdiagnosing late-life TBI-related neurodegeneration as Alzheimer’s disease, resulting in ineffective treatment approaches. Further work is needed to characterize post-TBI neurodegeneration.
The study is published in the journal JAMA Neurology.
Source: Mount Sinai Health System