An Oireachtas committee has heard that head injuries in sport can no longer be ignored and should be recognised as a public health issue.
Professor Colin Doherty, Consultant in Clinical Medicine at Trinity College Dublin, warned that routine collisions in sport may be "driving long-term brain injury".
He said there is now a "body of scientific and clinical evidence" on recurrent head injury in sport that "can no longer be ignored".
"The evidence has reached a point where inaction is no longer neutral. It carries its own risks," Professor Doherty told a Committee on Arts, Media, Communications, Culture and Sport.
The consultant said the issue now requires "coordinated national attention".
"Recurrent head injury in sport, including both concussion and the much more frequent sub-concussive impacts that do not cause immediate symptoms, is associated with long-term risks to brain health," said Professor Doherty.
He called for the establishment of a "national, multi-stakeholder clinical and policy group to develop consistent, evidence-based guidance across all sports" and for a publicly funded National Concussion Centre.
Professor Doherty also said the development of a register to monitor concussions and head impact exposure over time is needed, as well as sustained investment in research to "better understand risk, identify vulnerable individuals, and develop effective interventions".
The expert stressed the need for a focus on prevention, particularly among young athletes.
He said recent research from Trinity College Dublin and St James's Hospital has provided some of the "clearest insights to date into what may be happening in the brains of athletes exposed to repetitive head impact".
Professor Doherty said using advanced imaging techniques they have identified that a "significant proportion" of retired athletes show "persistent disruption of the blood-brain barrier, a critical protective system that normally regulates what enters and leaves the brain".
He said in some people this disruption remains years and even decades after they have stopped playing sport.
"This is not a transient injury. It appears to represent a chronic condition," he said.
Professor Doherty said there have also been "well-documented cases" of Irish athletes who have died with "full blown dementia"
Professor Doherty said this disruption "correlates with measurable cognitive decline, particularly in memory function".
The long-term changes also cannot be explained "simply by the number of diagnosed concussions an athlete has sustained", he said.
"Rather, they are more closely associated with the cumulative exposure to repetitive head impacts over time," said Professor Doherty.
He said while concussion management is "critically important", it is no longer enough.
The consequences of repetitive sub-concussive exposure now being clearly seen, said the professor.
He said former athletes have presented with symptoms of Traumatic Encephalopathy Syndrome, including "cognitive impairment, mood disturbance, and behavioural changes".
Professor Doherty said there have also been "well-documented cases" of Irish athletes who have died with "full blown dementia", also known as Chronic Traumatic Encephalopathy (CTE).
He said their research work has also shown for the first time "emerging evidence of ongoing brain inflammation long after retirement, suggesting that these injuries may trigger long-lasting biological processes that continue well beyond an athlete’s playing career".
He raised concerns that modern sport, particularly at elite levels "increasingly" celebrate physical intensity and collision
"This is often framed positively, as resilience and commitment. But it also risks normalising repeated head impacts in a way that may not be compatible with long-term brain health," he said.
He said concussion protocols vary between sporting bodies with, sub-concussive impacts remaining "largely unmeasured and unregulated".
Responding to a question from Fine Gael senator Evanne Ní Chuilinn, former professional rugby player Andrew Dunne said there has been a "complete reversal" around the attitude of coming off the field after a head injury.
When Fianna Fáil senator Alison Comyn asked if more research is needed on female athletes, Professor Matthew Campbell from the Smurfit Institute of Genetics said the female brain may be more susceptible to concussion "for reasons we don’t fully understand".
"We need to figure that out," he said.
"We may see down the line instances of CTE predominantly in women compared to men," said Professor Campbell.
Fianna Fáil TD Peter 'Chap' Cleere asked if the speakers could reassure parents that their children playing sport are fully protected from accumulative brain injury.
"I can’t," said Professor Doherty.
Mr Dunne said the benefits of sport "far outweigh the negatives".
However, when asked by Independent senator Rónán Mullen if he would discourage children from playing any sport, he raised the dangers of physical sports without a ball, including boxing and mixed martial arts.
