What is CTE and why does it matter for Irish athletes?

RTÉ News​

03-06-2025

Analysis: Brain injuries in sport are a growing public health issue that affects players at all levels, from local community teams to seasoned professionals
By Chris Greene, RCSI
Whether it's a clash of heads during a rugby tackle, a late hit in Gaelic football, or a crunching collision on the soccer pitch, head impacts in sport are unfortunately part of the game. But what are the long-term consequences? And what should we be doing about them, especially here in Ireland?
Brain injuries in sport aren't just a concern for elite athletes or international stars, they're a growing public health issue that affects players at all levels, from local community teams to seasoned professionals. In the United States alone, an estimated 1.6 to 3.8 million sports-related concussions occur every year. But not all head knocks result in a full-blown concussion. In fact, many more go under the radar as "sub-concussive" impacts, blows that might not cause obvious symptoms but still impact the brain.
There is mounting evidence that it is the cumulative effect of these repeated, lower impact hits; not just the number of concussions, that plays a key role in the development of a serious condition called chronic traumatic encephalopathy (CTE).
From RTÉ Radio 1's Saturday with Colm Ó Mongáin, Ombudsman waiting eight years for children's sport concussion policy
What is CTE?
CTE is a progressive brain disease linked to repeated head injuries. It's been seen in boxers, American footballers, rugby players, and increasingly in other contact sports like soccer or MMA. At present, it can only be definitively diagnosed after death, during an autopsy. Neuropathologists look for an abnormal build-up of a protein called tau, which clusters around small blood vessels in the brain. This build-up appears to damage nearby brain tissue and over time may lead to memory loss, mood swings, and confusion.
Because diagnosing CTE in living individuals remains a challenge, researchers have developed a set of clinical guidelines called Traumatic Encephalopathy Syndrome (TES). Think of TES as a way to spot red flags like memory problems or changes in behaviour in people with a history of head injuries. These criteria, updated by the National Institute of Neurological Disorders and Stroke (NINDS) in 2021, were developed by studying confirmed CTE cases.
While TES does not provide a definitive diagnosis, it indicates the possibility of trauma-related brain injury. Ongoing international projects, like DIAGNOSE CTE, are trying to find ways to detect signs of the disease earlier, but we're not quite there yet.
From CNN, Chief Medical Correspondent Dr. Sanjay Gupta explains the causes and symptoms of chronic traumatic encephalopathy
What's the role of the blood-brain barrier?
One of the most important and least understood players in this story is something called the blood-brain barrier (BBB). It's a kind of security gate that protects the brain from harmful substances in the bloodstream. Disruptions to the BBB have been seen in many neurological disorders, including traumatic brain injury. In CTE, researchers have found that the protective barrier may start to leak, allowing toxic proteins or inflammatory molecules to seep into brain tissue.
Our research group, alongside others, has found that athletes exposed to repetitive head injury, even without a diagnosed concussion, can show signs of this barrier breaking down. It's not just in American football or boxing; similar patterns are being investigated in Irish rugby and GAA players too.
Ireland isn't just watching from the sidelines. A collaborative project between RCSI University of Medicine and Health Sciences, Trinity College Dublin, and St James's Hospital is exploring how repeated head trauma affects the blood-brain barrier and how this might contribute to memory issues or cognitive decline in later life.
The project, funded by Research Ireland, uses advanced imaging techniques, such as dynamic contrast-enhanced MRI, to measure BBB health in retired athletes. What's striking is that even years after leaving the sport, some former players still show signs of brain changes. The next step is to understand how this relates to things like depression, memory loss, or dementia.
Why it matters
Traumatic brain injuries have been linked with a higher risk of conditions like dementia, mood disorders, and even suicide. In the US, retired American footballers are five times more likely to develop dementia. But this isn't just an American story. A Scottish study found that former professional soccer players were 3.5 times more likely to die from a neurodegenerative disease. Swedish studies have shown similar findings.
While Irish data is still emerging, there are real concerns for former rugby players here at home. Rugby only turned professional in the mid-1990s, so we're just beginning to understand the long-term impacts on those who played at the top level.
From RTÉ Radio 1's Today with Claire Byrne, Consultant Neurologist at the Mater Professor Tim Lynch on concussions in sport
A game of balance
Sport is a vital part of Irish life. From weekend GAA matches to the roar of the Aviva on a Six Nations Day, it brings people together, builds community, and supports mental and physical health.
But with this passion must come responsibility. Protecting brain health isn't about taking the joy out of sport, it's about ensuring that players can enjoy those benefits long after the final whistle. That means better awareness, smarter rules, improved protective equipment, and ongoing research into how to detect and treat brain injuries early.
It also means listening to former players, parents, coaches, and medical professionals as we build a safer future for the next generation of Irish athletes.