Groundbreaking Trinity research reveals “leaky” brain barrier as driver of chronic brain damage in retired combat and collision sports athletes

Posted on: 18 March 2026

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.”  

A comparison of the MRI brain scans of people in different cohorts. Left: Control (normal MRI brain scan); Middle: Non-extensive (red/blue pixels showing non-extensive leakage of the BBB); Right: Extensive (red pixelation showing extensive BBB leakage in a retired symptomatic individual). Image: Prof. Matthew Campbell et al. Trinity College Dublin.

 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.”

The research was funded by Research Ireland, the Canadian Institute of Health Research, the European Research Council (ERC), the StAR programme at RCSI and The Moran family foundation.

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