Summary: New research has identified a leaky blood-brain barrier (BBB) as the primary mechanism linking repetitive head injuries to long-term cognitive decline in retired athletes. By comparing MRI scans of living rugby players and boxers with post-mortem tissue from athletes diagnosed with Chronic Traumatic Encephalopathy (CTE), the team discovered that this barrier remains compromised years after retirement.
This “leaky gate” allows inflammatory proteins to seep into brain tissue, triggering a toxic cascade that leads to the buildup of p-Tau, a protein associated with Alzheimer’s and dementia. The study suggests that the damage from contact sports is a chronic, ongoing process rather than a static injury.
Key Facts
- Persistent Leakage: The blood-brain barrier—the brain’s “security gate”—remains leaky in some athletes for years after they stop playing, long after initial impacts occur.
- Inflammatory Cascade: Barrier disruption allows harmful proteins to infiltrate the brain, directly correlating with lower scores in memory and executive function tests.
- Early Warning System: Advanced MRI scans focusing on the BBB could potentially identify at-risk athletes while they are still active, serving as a proactive screening tool.
- Treatment Potential: The discovery opens a new therapeutic window, suggesting that “sealing” the leaky barrier with drugs could slow or stop the progression of neurodegeneration.
Source: TCD
Groundbreaking research, led by teams at Trinity College Dublin and the FutureNeuro Research Ireland Centre, has pinpointed the mechanism linking some sports injuries to poor brain health in retired athletes.
The research, published today in leading international journal Science Translational Medicine, has identified a breakdown in the blood-brain barrier (BBB) as the key link between repetitive head injuries (RHIs) and long-term brain health issues in this cohort.
The BBB acts as a “security gate”, letting in essential nutrients while keeping harmful toxins and inflammatory cells out. But when “leaky” it cannot perform this security job properly and 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 RHIs this gate remains leaky years after they have left the field.
By using advanced MRI scans on retired rugby players and boxers and cross referencing data obtained in post-mortem brain tissue from athletes diagnosed with Chronic Traumatic Encephalopathy (CTE), the team discovered that this leakage allows inflammatory proteins to seep into the brain.
These inflammatory proteins then trigger a cascade of damage, including the build-up of p-Tau, a toxic protein associated with Alzheimer’s Disease and other forms of dementia.
“Even years after retirement, retired athletes showed significant BBB disruption compared to age-matched controls,” said Prof. Matthew Campbell, Professor of Neurovascular Genetics and Head of Trinity’s Genetics Department, who led the work with Prof. Colin Doherty, Professor of Epileptology and Head of Trinity’s School of Medicine. “This suggests that the damage from head impacts is a chronic, ongoing process.”
“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.”
What is the impact of this work?
“The study highlights that MRI scans focused on the BBB could serve as an early warning system, identifying athletes at the highest risk for future brain disease while they are still living and (potentially) playing,” said Dr Chris Greene, first author of the paper and FutureNeuro StAR Lecturer in RCSI University of Medicine and Health Sciences.
The findings represent a major step forward on their own, but the researchers emphasise that they have significant potential to herald the beginning of an entirely new chapter in sports medicine. Specifically, they suggest that:
- Early intervention trials could now investigate whether sealing the “leaky” barrier through new or existing drugs could slow down or even stop the progression of brain damage in at-risk athletes.
- Future research should 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 now aim to expand the work to include a wider range of athletes, including those in women’s sports and amateur sports, to explore if these findings apply across all levels of collision/combat sports.
Prof. Colin Doherty added: “We are now at a critical juncture in how we, as a society, accept what is 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.
“Based on the evidence we now have from this study we should be calling for a pro-active 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.”
Key Questions Answered:
A: The brain’s “security gate” (the blood-brain barrier) stays broken. Because it never properly closes, inflammatory toxins continue to seep in and damage neurons long after the last hit on the field.
A: We’re getting closer. This study shows that BBB-focused MRI scans can identify the specific “leakage” that correlates with lower memory scores, potentially flagging high-risk athletes years before symptoms appear.
A: That’s the next frontier. Now that we know the BBB is the problem, researchers are looking at drugs that can “seal” the barrier, which could theoretically stop the progression of dementia in its tracks.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this CTE research news
Author: Thomas Deane
Source: TCD
Contact: Thomas Deane – TCD
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Blood-brain barrier disruption, traumatic encephalopathy, and cognitive decline in retired athletes” by Chris Greene, Declan Brennan, Sheida Mirloo, Ruairi Connolly, Jeffrey O’Callaghan, Avril Reddy, Jeff Henderson, Gergő Porkoláb, Adam McGlinchey, Nicole Hanley, Siobhan Hutchinson, James F. M. Meaney, Michael Farrell, Sarah L. Doyle, Alon Friedman, Colin P. Doherty, and Matthew Campbell. Science Translational Medicine
DOI:10.1126/scitranslmed.adu6037
Abstract
Blood-brain barrier disruption, traumatic encephalopathy, and cognitive decline in retired athletes
Cerebrovascular disruption has been implicated in the pathophysiology of head trauma and chronic traumatic encephalopathy (CTE). However, the long-term consequences of repetitive head trauma on blood-brain barrier (BBB) integrity and its link to cognitive function remain unknown.
Here, using dynamic contrast–enhanced magnetic resonance imaging (DCE-MRI), we show that BBB disruption can be detected years after the retirement of combat and collision sports athletes (n = 47) from their respective sports.
A subgroup of individuals (n = 17) with extensive BBB disruption displayed worse cognitive decline compared with those with less extensive BBB disruption. Commonly used systemic markers of central nervous system injury and neurodegeneration were of limited utility; however, a greater systemic inflammatory burden with a higher proportion of circulating monocytes was associated with cognitive decline in the retired athletes.
Transcriptomic analysis of these peripheral immune cells revealed dysregulation of the complement system and vascular developmental pathways. Altered expression of complement receptors, including C5AR1, ITGAM, ITGB2, and CD59, a potent inhibitor of the membrane attack complex (MAC), was associated with BBB disruption and cognitive decline.
Postmortem brain tissues from those with confirmed cases of CTE showed MAC deposition around cerebral blood vessels. Bioinformatic analysis of single-nucleus RNA sequencing data from postmortem individuals with CTE revealed microglia-endothelial cross-talk, which may mediate complement dysregulation.
Together, our data suggest that sustained systemic inflammation and persistent BBB disruption are associated with the long-term outcome of repetitive head trauma.
