A “leaky” blood-brain barrier is the “key link” between repetitive head injuries and poor long-term brain health in retired athletes, new research from Trinity College Dublin has found.
Sport-related concussion and subconcussive injuries are a matter of growing public health concern worldwide, due to its connection with long-term brain damage, dementia and fatal bleeding in or around the brain.
These injuries have been linked to a number of sports including rugby, boxing, soccer and MMA, among others.
Research published in the international journal Science Translational Medicine on Wednesday found the blood-brain barrier (BBB) acts as a “security gate” that lets in essential nutrients while keeping out harmful toxins and inflammatory cells.
When the membrane is “leaky”, it cannot perform this function properly.
As a result, it becomes associated with the cognitive decline and neurological damage seen in some former professional collision and combat sports athletes, including rugby players and boxers.
For the first time, the researchers have shown that in some retired athletes with a history of repeated head injuries, this gate remains leaky years after they have left the field.
The research used advanced MRI scans on retired rugby players and boxers and cross-referenced data obtained in postmortem brain tissue from athletes diagnosed with Chronic Traumatic Encephalopathy (CTE), a progressive, incurable neurodegenerative disease caused by repeated head trauma.
According to the findings, the leakage in this barrier allows inflammatory proteins to seep into the brain, which triggers damage such as the build-up of a toxic protein associated with Alzheimer’s disease and other forms of dementia.
Matthew Campbell, professor of neurovascular genetics and head of Trinity’s genetics department, said even years after retirement, retired athletes showed significant BBB disruption compared to non-athletes of the same age.
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“This suggests that the damage from head impacts is a chronic, ongoing process,” he said.
“We found that retired athletes with the most extensive ‘leakage’ in their brain barrier also scored significantly lower on cognitive tests, specifically those measuring memory and executive function.”
Dr Chris Greene, first author of the paper and FutureNeuro StAR lecturer in the Royal College of Surgeons in Ireland, said the study highlights how MRI scans focused on the BBB could serve as an “early warning system”.
This, he said, could identify athletes at the “highest risk for future brain disease while they are still living and (potentially) playing”.
According to the researchers, the findings have significant potential to improve sports medicine, through early intervention trials investigating whether sealing the leaky barrier through new or existing drugs could slow down or stop the progression of brain damage in at-risk players.
They called for future research to follow current professional players throughout their careers to determine exactly when the barrier starts to fail, information that could help sports organisations refine return-to-play protocols and safety regulations.
The researchers said they intended to expand the work to examine a wider range of sports, including women’s and amateur sports, to explore if the findings apply across all levels of collision and combat sports.
Colin Doherty, professor of epileptology and head of Trinity’s School of Medicine, said society was at a “critical juncture” in deciding what’s allowable in the context of sports-related head trauma.
“Especially for the amateurs and under-18s involved in collision and combat sports such as rugby where the duty of care falls on teachers and amateur coaches who are usually parents themselves,” he said.
“Based on the evidence we now have from this study, we should be calling for a proactive approach from Government to address what is now an important public health issue, not one that the sporting codes can be left to manage alone.”