Researchers revealed on Thursday that Farmer had been posthumously diagnosed with Stage III chronic traumatic encephalopathy (CTE) following tests on the former champion ruckman's brain.

Farmer is the first AFL player to be diagnosed with the disease believed to be caused by repeated head knocks and concussions, which is only able to be diagnosed after death.

Farmer, who played 101 games for Geelong and captained the club from 1965-67, died last year aged 84 after a long battle with Alzheimer's.

Head of neuropathology at the Royal Prince Alfred Hospital and clinical associate professor at the University of Sydney, Michael Buckland, is the founder of the Australian Sports Brain Bank that conducted the research.

He called on the AFL to do more to reduce the incidence of head knocks.

The league pointed to advances in concussion protocols in a statement released on Thursday and AFL boss Gillon McLachlan pledged to continue to explore the sensitive issue.

"I want to acknowledge and thank the Farmer family and Polly Farmer for their significant action in donating his brain and the learnings that we'll get from that," McLachlan said.

"Clearly it's about prevention, diagnosis and research.

"We will continue to learn."

The disease has become increasingly prevalent in NFL, boxing and soccer, while two former Rugby League players, including legendary Canterbury player and coach Steve Folkes, have been diagnosed.

Professor Buckland applauded the AFL's moves to tighten concussion protocols but said the sport must work towards further reducing the incidence of head knocks that don't necessarily result in concussion.

"There seems to be an exposure relationship between repetitive head knocks, whether they be concussive or sub-concussive, and CTE," he said.

"One thing we'd like the conversation to start focusing on is how we reduce exposure to these repetitive head knocks.

"This might be hundreds a year over many years just like smoking - it's not one cigarette that kills you, it's just that repetitive exposure."

Prof Buckland added that it was still early days in terms of research into the incidence of CTE in AFL players, with more funds required to continue that work.

Long-time concussion campaigner Peter Jess, who has advocated for a class action of concussed past players against the AFL, felt vindicated by the findings.

"Basically what this does is it tells us that the science has validated what we've been saying," Jess told SEN.

"This is the clinical evidence of what the outcome is from repetitive collisions in our sport. This is what we're seeing now in the current cohort of players."

As well as his three Sandover Medals, Farmer was runner-up for the Brownlow Medal and was three times named in the All-Australian team.

After winning a premiership with the Cats in 1963, he was also the first indigenous coach in VFL/AFL history.

Australian Associated Press