Over half of brains donated to the Australian Sports Brain Bank have signs of chronic traumatic encephalopathy (CTE), a degenerative brain disease associated with repeated blows to the head, researchers have found.
Data from the first three years of the national brain bank shows that of the first 21 donors — all of whom participated in sports with risks of repetitive head injury — all but one donor had some form of neurodegeneration, including 12 who were found to have CTE.
"The 21 donors came from a range of sports, but 17 of them either came from AFL or one of the rugby codes," said neuropathologist Michael Buckland from Sydney's Royal Prince Alfred Hospital and the University of Sydney.
CTE, which can only be diagnosed post-mortem, is associated with behavioural, mental and cognitive impairments, including memory loss, personality changes and depression.
Symptoms typically appear years or even decades after brain injury is sustained.
CTE was first found in boxers more than 90 years ago (originally known as punch-drunk syndrome), but has more recently been described in former players of American football, ice hockey and soccer.
"Almost all of our donors, they or their families, signed up for the brain donation because they were exhibiting signs or symptoms that something was wrong with their brain," Dr Buckland said.
"So it's very much a selected population, and we can't make any claims about the prevalence of CTE in the sporting community."
But Dr Buckland said the preliminary findings, published today in the Medical Journal of Australia, confirmed the existence of CTE in former Australian sports players, after a handful of cases had been identified in recent years.
"Our main purpose of the Sports Brain Bank was to actually see if Australian sports players also had CTE … and once we looked at that at-risk population, CTE was easy to find," Dr Buckland said.
Young and old affected, several died by suicide
The researchers found three of the brain donors with CTE were under the age of 35, and six of the 12 donors with CTE had died by suicide.
Dr Buckland said the donor group was too small to draw any firm conclusions about whether CTE was a possible risk factor for suicide, but said the findings were nonetheless "alarming".
"I do think it's something that requires further investigation and investment," he said.
The researchers identified CTE in the brains of older, former sports professionals with long playing careers, as well in their younger counterparts.
"There were definitely younger people that had played under modern concussion guidelines," Dr Buckland said.
"The other disturbing thing was that it's not just restricted to professional players — there were people that had played at either the amateur level or the semi-professional level that also had CTE."
Reducing head impacts in sport
In recent years, there have been significant rule changes in several sporting codes to reduce the chances of impact to the head, and rule changes around dealing with concussed players.
Both the NRL and AFL now sideline concussed players for a minimum of 11 and 12 days respectively, to ensure players are fully recovered before they return to competition.
But Dr Buckland said it was repeated exposure to smaller, "subconcussive" head knocks — which don't lead to a loss of consciousness but can still damage the brain over time — that predominantly leads to CTE.
"It's much like your risk of lung cancer if you're a smoker," he said.
He said the evidence to date, while limited, suggests CTE is more closely related to the number of years a person has played sport, and the age they were first exposed, as opposed to the number of concussions they've had.
"While a player might have maybe a few concussions over a couple of years, they'll probably have thousands of subconcussive blows," he said.
"They're fine, they get up and keep playing, and it's just a good contest of the ball or whatever.
"But it's likely it's the cumulative effect of those many, many subconcussive hits that leads to CTE."
Whether modern concussion guidelines adequately addressed the risks of concussion was a different question to whether sporting codes took the risk of CTE seriously enough, he said.
"I think they manifestly downplay the association between repetitive head injuries and CTE, and I would think in the future if the codes took this seriously, they would not only have concussion policies, but CTE policies."
In recent years, legal action and class actions on behalf of former athletes have been taken against both the AFL and NRL, similar to legal action by former NFL players in America that has resulted in $US500 million in claims.
The researchers called on clinicians and policymakers to develop measures that "further mitigate the risk of sport-related repetitive head injury", which Dr Buckland said should address two key risk factors.
"How do we reduce cumulative lifetime exposure to repetitive head injury?
"And should we be seriously debating the age of first exposure to sports-related repetitive head injury?"
Caution needed when interpreting findings
Neuroscientist Sandy Schultz from Monash University said the Australian Sports Brain Bank was an "important initiative", and that the findings were consistent with larger scale studies in the US and UK.
"It isn't surprising that they would find neurodegenerative disease or CTE in a highly biased sample like that," Dr Schultz said.
"We saw the same thing happen in the initial studies coming out of North America."
He said it was meaningful to have evidence of CTE in former Australian collision sport athletes, but he urged caution when interpreting the results.
"You've got to be cautious in how much you take away from a study like this because it is very small … and a highly, highly biased sample," he said.
Dr Schultz said although it was clear that repeated head trauma increased the risk of CTE, it was very difficult to ascertain the prevalence of the disease in athletes, and that some studies suggested it was low overall.
"But this is a good first step and hopefully [the researchers] can continue to build on this and publish more thorough and comprehensive studies down the line once they have the ability to do so."
Improving awareness and understanding
To date, the brain bank has received more than 600 donation pledges from amateur and professional sportspeople across Australia.
In addition to better understanding the prevalence of CTE, Dr Buckland said the goal of the research was to help develop a new means of diagnosing CTE during life, and potentially finding an effective treatment.
"People are going to have this for the next 20 or 30 years, so we need to find a way to diagnose it during life and treat it," he said.
"The goal is to prevent it in future generations by better understanding and addressing the risk factors."
For now, Dr Buckland said the brain bank was helping to provide some families with an increased awareness and understanding of what had happened to their loved ones.
The Australian Sports Brain Bank is currently looking for Australians who have played high-impact contact sports to donate their brain for research. You can find out more here.
