Doctors studying Chronic Traumatic Encephalopathy (CTE) in AFL players believe just like smoking, it's not one cigarette that kills you, it's repetitive exposure to head knocks that cause the degenerative brain disease.

Key points: Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease believed to be caused by repeated concussions or head injuries

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease believed to be caused by repeated concussions or head injuries Originally known as punch-drunk syndrome, it was found at autopsy in ex-boxers, but has now been linked to American footballers, and players in ice hockey, rugby league and soccer

Originally known as punch-drunk syndrome, it was found at autopsy in ex-boxers, but has now been linked to American footballers, and players in ice hockey, rugby league and soccer CTE ranges from the mildest form in stage one to the most severe in stage four — former Australian Rules great Graham 'Polly' Farmer was found with stage three

Researchers at the Australian Sports Brain Bank, in conjunction with the University of Sydney, have confirmed the first case of CTE in an Australian Rules footballer, after studying the brain of former champion Graham "Polly" Farmer.

"At 64 the player was diagnosed with Alzheimer's, with elements of depression or mood swings, explosivity, loss of attention and concentration, short-term memory loss and headaches," Clinical Associate Professor Michael Buckland said.

CTE can only be diagnosed during brain examination at autopsy and doctors say the only known risk factor in developing CTE is repetitive head injury.

Signs and symptoms of concussion Loss of consciousness after impact

Loss of consciousness after impact Confusion, disorientation, loss of coordination or balance

Confusion, disorientation, loss of coordination or balance Memory impairment

Memory impairment Dazed or vacant stare

Dazed or vacant stare Headaches, neck pain, feeling pressure in the head

Headaches, neck pain, feeling pressure in the head Blurred vision, dizziness

Blurred vision, dizziness Nausea or vomiting

Nausea or vomiting Irritability, feeling more emotional, nervous or anxious Source: AMA

A protein called Tau is found in the brain — it normally helps with the structure of neurons, but if released in a wider environment, it can become toxic to brain cells and eventually kill them.

"It depends on how far the progression goes — we have stage 1 which is minimal through to stage 4, where there is a loss of brain tissue globally," Assistant Professor Alan Pearce from La Trobe University told ABC Melbourne.

"Polly was diagnosed with CTE stage 3.5, so it's on the severe scale."

CTE was originally known as punch-drunk syndrome, as it was found in a lot of ex-boxers.

But it has more recently been found in the brains of former players of several sports, including American football, ice hockey and soccer.

Last year Professor Buckland — who is also the head of neuropathology at the Royal Prince Alfred Hospital — identified CTE in the brains of two former rugby league players including Canterbury Bulldogs coach and player Steve Folkes.

It has been thought that concussion is the major concern in developing CTE, but those studying the disease fear all head knocks can be damaging and need to be prevented.

"We need to draw attention to these repetitive sub concussive knocks, so knocks that don't necessarily result in a concussion, from American football the severity of CTE is not related to the number of concussions it's more closely related to the years of play," Buckland said.

The AFL released a statement saying it had not seen the detailed report, but it supported the work of the Australian Sports Brain Bank and welcomed "the learnings that may come from their ongoing research".

The league said it had already "further strengthened" the concussion management guidelines for the 2020 AFL and AFLW seasons.

"The AFL will continue to invest in research to better identify and manage concussion and other brain related trauma at all levels of the game," the statement read.

Cultural awareness still an issue

The researchers raised concerns some AFL players were still not taking the issue seriously.

"We need to address cultural awareness, we still see players wearing it as a badge of honour, thinking I can take anything, I will run through walls and trying to mask their symptoms because of that continuing that tough athlete mentality even in D grade amateur," said Adjunct Professor Alan Pearce, La Trobe University.

He said players must realise even if concussion symptoms have resolved their brain may not have recovered fully.

"The same way a player would be aware of a knee or Achilles or shoulder and would come off and get checked out, we need the same approach with head injuries," Professor Pearce said.

"There needs to be objective markers to come into the assessment — and clinical diagnosis — so I think we can actually do better."

Farmer a Legend of the game

Graham 'Polly' Farmer broke down barriers as the first Indigenous football superstar. ( ABC News )

Farmer was one of the inaugural inductees and "Legends" of the game to the Australian Football Hall of Fame in 1996, along with the likes of Ron Barassi, Kevin Bartlett, Jack Dyer, Malcolm Blight and John Coleman.

The Western Australian, who played 101 games for Geelong and captained the club from 1965-67, died last year at the age of 84 after a long battle with Alzheimer's.

As well as his three Sandover Medals (best and fairest in the Western Australian Football League), he was runner-up for the Brownlow Medal when playing at Geelong and was three times named in the All-Australian team.

He won the 1963 VFL premiership with the Cats, after earning five WAFL flags with West Perth.

Farmer was also named as captain of the Indigenous Team of the Century in 2005 and he was the first Indigenous coach in VFL/AFL history.

Need for sports to evolve

Assistant Professors Michael Buckland (L) and Alan Pearce spoke to the media about the CTE finding for Polly Farmer. ( ABC News: Patrick Galloway )

Those behind the study aren't calling for a nanny-state solution to ban contact sports, but emphasise the need to educate people about the risks of suffering many head knocks over years.

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"We need to understand that [the timetable for] return to play seems to be quite individual, we don't want that next generation of players asking the same question we are getting now," Professor Pearce said.

More research would help shed light on the ramifications for players in all different levels and codes.

Most of the data has been taken from studies of American football, where the risk of CTE doubles for every 10 years of play.

"We are still trying to quantify risks with AFL, NRL and union, we have to be doing Australian research in Australian sports — we need to look at this as fast as we can with as much help as we can," Professor Buckland said.

Administrators also have a role to play in preventing head knocks.

"These sports have evolved and continue to evolve over time, as in rugby league what's played now is very different to how it was played when I was growing up — this conversation [on CTE] can feed into the evolution of these sports," Professor Buckland said.

In America there is a push to reduce players exposure to head knocks in children.

"Banning tackling in children's football, if you delay them for ten years you've halved their CTE risk — prevention is the best cure," said Professor Pearce.

The AFL has been commended for making some improvements.

"In the last five-to-six years the AFL with their head injury assessments have done good moves towards recognising head injuries in football and making sure that the return to play protocols are enforced as best possible," Professor Pearce said.

Ex-AFL player supports research developments

AFL premiership player John Barnes suffers from crippling memory loss, mood swings and epilepsy, symptoms that he said were a direct result of head knocks he sustained during a career spanning 15 seasons.

Barnes, who played 202 matches for Geelong and Essendon, is heading a planned class action against the AFL and said more than 100 footballers had joined.

He cannot be diagnosed with CTE as he is still alive, but welcomed the research developments.

"It's fantastic to know that there is a reason and an answer as to why blokes are going through what they are going through," Barnes said.

"I am glad the family signed up to the brain registration, it gives closure to something we already knew. I've had so many amazing calls of support this morning and I think it has opened eyes to what our sport actually does."

John Barnes sustained a number of head knocks during his AFL career. ( AAP: Julian Smith )

Barnes, who won an AFL premiership with the Bombers in 2000, said he believed he sustained head knocks in every league match he played.

"I probably copped 15 to 20 a game, concussions where you've lost your marbles probably a dozen [times]," he said.

"Tackles, bumps, blocks, knees to the head. On top of training, you're probably copping 50 knocks over a seven-day period, so it adds up."

Barnes, 50, said the head knocks he sustained had a dramatic impact on his day-to-day life.

"It's turned my life upside down, I am now like a toddler, which is very frustrating," he said.

"I get short-tempered, I forget stuff, my maths is atrocious. I don't think the Weet-Bix belongs in the fridge or the milk in the cupboard, I'm often wandering around the supermarket and have no idea why I am there."

Farmer case the first of many, says Smith

A former AFL player who suffered multiple concussions during his career said the confirmed case of CTE would be the first of many for the code.

Former Melbourne player Shaun Smith said more must be done to prevent current players from developing mental illness like he has had as a result of brain injury.

"I think it's horrible, some players are being knocked out and returning to the field next week, which in my eyes is pretty poor," Smith said.

"You can obviously manage a concussion if its managed right, you may have to miss five six seven weeks."

Players' agent Peter Jess, who has been outspoken on the issue of concussions in AFL, has urged the league to review its "return-to-play" guidelines for players who have suffered concussion.

Jess says recent changes to the AFL's guidelines don't go far enough because concussed footballers are allowed to return to play just five days after being given the "all clear".

"The evidence that we see tells us that window of vulnerability is four weeks, so if you return players under that period you are putting them at risk," he said.

Current players back AFL

Collingwood captain Scott Pendlebury said he was confident the AFL had suitable concussion protocols in place.

"In my time it has improved immensely," he said.

"It used to be how hard you are and how — if you got a big hit — you just get back out there and that player was almost lauded. If there's a big hit [now] the guys are off and most likely don't play the next week."

Port Adelaide's Travis Boak agreed that the AFL had taken the issue of concussion seriously.

"There's no doubt it is a big part of contact sport and the AFL," he said.

"But I think we have really good parameters in place to protect our players to make sure that we are OK and I have complete faith in the AFL, the AFLPA (AFL Players Association) and our doctors to make sure we are looked after.

"If we do get a head knock there's a lot of boxes we have to tick to go back on, so I am not too concerned if we are being looked after enough."

ABC/AAP