Irish scientists identify link between head injuries in contact sports and Alzheimer's and dementia

Repetitive head injuries in sports such as rugby can lead to poor brain health, researchers found. File picture: Diarmuid Greene/Sportsfile 

Irish scientists have identified the mechanism linking poor brain health to sports injuries in contact sports such as rugby and boxing.

The research, by teams at Trinity College Dublin and the FutureNeuro Research Ireland Centre, has identified a breakdown in the blood-brain barrier (BBB) between repetitive head injuries and long-term health issues, including Alzheimer's disease and other forms of dementia.

The blood-brain barrier 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 repetitive head injuries, 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, the team discovered 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.

Dr Chris Greene, FutureNeuro StAR lecturer in RCSI University of Medicine and Health Sciences, said: "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.”

The researchers said their findings had "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 Doherty said: “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.”