Largest ever study identifies link between TBI and Parkinson’s, but not Alzheimer’s.
The CDC estimates that more than 1.3 million Americans visit an emergency department each year because of a TBI-related injury. The late effects of TBI are of great interest, however, studies characterizing these effects are limited. Now, a study from researchers at Mount Sinai and the University of Washington shows that traumatic brain injury (TBI) with a loss of consciousness (LOC) may be associated with later development of Parkinson’s disease but not Alzheimer’s disease or incident dementia. The team state that their research contradicts past studies which identify a link between TBI and Alzheimer’s disease. The study is published in the journal JAMA Neurology.
Previous studies show that TBI has come to the forefront of both the scientific and popular culture. Specifically, sports-related concussions or mild TBI has garnered great interest with a large amount of research in this area. Recent studies have come to light that link TBI to neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases, as well as certain psychiatric diseases. However, whether these associations are causative is yet to be determined, with the global medical community reliant on the populace aging to fully gauge the impact of TBI on the aging brain. The current study investigates whether TBI with loss of consciousness is associated with an increased risk for clinical and neuropathologic findings of Alzheimer disease, Parkinson disease, and other dementias.
The current study analysed injury data from 7,130 older adults. 865 people had suffered TBI with LOC at some point before the study began, and of these 865 patients, 142 had been unconscious for more than one hour. The researchers evaluated 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. Roughly 23% of the study group had brain autopsies, and in that group, any link between TBI and neuropathological findings were investigated.
Results show no statistically significant relationship between TBI with LOC and dementia risk was discovered when the group with TBI with LOC was compared with the 1,537 patients who developed dementia during the study. Data findings for Alzheimer’s disease, diagnosed in 1,322 study participants, were similar. However, regression data showed a strong association between TBI with LOC greater than an hour and Parkinson’s disease, numbering 117 cases during the study.
The lab state findings for the 1,652 autopsy cases showed no association between TBI with LOC and beta amyloid plaques or neurofibrillary tangles, the hallmark indicators of Alzheimer’s disease. They go on to add that, however, the autopsies found an increased risk for Lewy bodies in TBI with LOC less than an hour and an increased risk of cerebral microscopic stroke in TBI with LOC more than an hour. The group note that, to their knowledge, this is the largest study ever on this topic.
The team surmise that their findings suggest that some individuals with a history of TBI are at risk for late-life neurodegeneration but not Alzheimer’s disease. For the future, the researchers state that they want to identify and treat post-TBI neurodegeneration while people are still alive, and to do this, they first need to understand the disease. They conclude that prospective TBI brain donation studies can help the global medical community to characterize post-TBI neurodegeneration, identify risk factors, and develop effective treatments.