Do head injuries play a role in how early Alzheimer's sets in?
Recently, injuries related to contact sports have sparked a lot of worry that these events could lead to a deterioration of brain health in time.
According to a National Health Statistics Report from 2016, "From 2011 through 2014, Americans aged 5 years and over sustained an average [of] 8.6 million sports- and recreation-related injury episodes per year."
Dr. Munro Cullum — the neuropsychologist in charge of the research — and his colleagues drew their conclusions by looking at cases of Alzheimer's that had been confirmed postmortem.
This is the first time that this method was used in a study mapping the possible links between brain injury and neurodegenerative diseases.
The study's findings have recently been published in the journal Neuropsychology.
Despite the association found between TBI and Alzheimer's, the researchers still would not go as far as advising parents to keep their children away from contact sports. That, the authors add, is because we still don't know exactly how, and in which cases, head injuries increase the risk of neurodegenerative problems later in life.
"We need to be aware that brain injury is a risk factor, but parents shouldn't keep their kids out of sports because they fear a concussion will lead to dementia. This is a piece to the puzzle, a step in the direction of understanding how the two are linked."
Dr. Munro Cullum
Findings spur further questions
Dr. Cullum and team analyzed data sourced from 2,133 subjects whose diagnoses of Alzheimer's disease were confirmed postmortem.
They found that individuals who experienced a TBI accompanied by loss of consciousness for more than 5 minutes were, on the whole, diagnosed with Alzheimer's earlier than peers who had not sustained such head injuries.
These diagnoses seemed to come significantly earlier than in the case of people without brain injury — 2.5 years earlier, on average.
The researchers explain that the current study is set apart from previous, similar investigations by the fact that it found a high degree of association between dementia and a history of brain injury — namely, that Alzheimer's onset could be "accelerated" by up to 9 years.
Other studies, say Dr. Cullum and team, did not find any links between the two, and the researchers put it down to a less specific methodology when it comes to establishing a diagnosis of dementia.
However, the current study's authors point out that their findings give rise to new questions that call for an answer. These include:
- What underlying mechanism is at fault when TBI contributes to the onset of dementia?
- Do other factors influence the early onset, and if so, which?
- Who is most at risk in this context?
So far, the researchers hypothesize that brain injury-derived inflammation may play a role, and that interacting risk factors could include genetic makeup.
However, settling those questions may take years; as Dr. Cullum explains, medical records often do not include a full history of TBI, which makes it difficult to draw any clear conclusions based on existing data.
The scientists have already taken the first steps to try to remedy this problem, and they are actively involved in further studies that aim to clarify the links between head injuries and brain disorders.
"But," explains Dr. Cullum, "we have to wait 40 to 50 years until those college athletes are in their 60s and 70s to study them and know the outcome."
"That's going to be a long wait. We need researchers now to start collecting this information as part of their routine studies. Until we have more detail, all we can look at are correlations," he concludes.