A groundbreaking study on the degenerative brain disease, chronic traumatic encephalopathy (CTE), has revealed serious numbers behind the injury's impact.

ABC News has revealed rugby league players' brains, who were in their 20s, 30s, and 40s, were found to have CTE, which was diagnosed after their death.

The publication acquired the numbers, which were presented by molecular biologist Jennifer Cropley at the International Sports Concussion Conference on Tuesday.

The results showed that 150 brain donations from players who played contact sports were examined and conducted by the Australian Sports Brain Bank.

Of the 51 donated brains from people who had played rugby league, 31 were diagnosed with CTE. The players had competed at levels ranging from amateur to professional.

The recent findings do not mean that 31 out of every 51 rugby league players will develop CTE, as brain-bank donors are not considered representative of the broader playing population.

CTE's major cause occurs when there is repeated head trauma, which can cause cognitive impairment and behavioural changes.

It includes dementia, memory loss, paranoia, and progressive motor function loss.

With rugby league being one of the most high-octane and aggressive sports, it can leave NRL players at high-risk of developing the disease.

Among those diagnosed posthumously with CTE were former NRL player and premiership-winning coach Paul Green and former Manly Sea Eagles forward Keith Titmuss.

Titmuss died from exertional heatstroke in 2020, aged just 20, with his subsequent CTE diagnosis highlighting concerns about exposure to repetitive head impacts from a young age.

Green's widow, Amanda, spoke with ABC about the worrying statistics surfacing on brain injuries and is urging more people to donate their brains to gather greater information and awareness.

"Now that we know what we do about this disease, I feel a massive responsibility, as we all should, to protect the brain health of the next generation of young athletes," Ms Green told ABC.

"I owe it to my kids and their sports-loving mates. We need to ensure they don't make the same mistakes as our generation did. The key here is to pledge our brains and support the incredible and potentially lifesaving work of the Australian Sports Brain Bank."

Ms Green says she was unaware of what CTE was until her partner's passing.

"I had been involved in the highest level of professional sport in this country and did not understand this disease we now know as CTE," she said.

"That was not OK. I didn't know what CTE was, and since Paul's diagnosis, I have constantly called for more education on the issue. People needed to understand this disease so no one else suffered in silence."

Leading neuroscientists and concussion experts have called for all contact codes to be reduced to non-contact forms until age 14, after further information around head injuries begins to emerge.

“No sport should accept repetitive head impacts before the age of 14,” neuroscientist Dr Chris Nowinski told The Sydney Morning Herald in 2022.

“Let's start there. Parents don't hit their own child in the head, and we need to remove this cultural veil that it's happening in sports is OK for the developing brain. It's not.

“That means in soccer there is no heading, and in the [other] football codes there is no tackling. You can play a tag or flag version of the game until age 14 and get all the benefits of exercise and teamwork without sowing the seeds for a brain disease that will kill some of them. It shouldn't be a debate.”