A groundbreaking new paper part-authored in New Zealand confirming the link between CTE and repetitive head injuries should be a watershed moment for sport… shouldn’t it?

In last night’s wild and at times baffling Bledisloe Cup encounter in Melbourne, All Black teammates David Havili and Sam Cane clashed heads when attempting to tackle the same player. Both subsequently failed Head Injury Assessments and were removed from the game, won 39-37 by the All Blacks.

Cane has endured many concussions over the course of his career. Last night was merely another reminder of the random brutality of the modern, gladiatorial game. There was another reminder just over a month ago. When the story dropped, the reaction was almost instantaneous.

“Huge moment,” one ex-All Black told me. Similar messages floated through a loose collection of former players and their families – ones who have been dealing with diagnoses of early-onset dementia.

The story claimed that researchers had found “conclusive evidence” that repeated head injuries (RHIs) caused chronic traumatic encephalopathy (CTE). A multi-university paper authored by some of the world’s most highly regarded neuroscientists, including three from New Zealand, and with the imprimatur of Harvard no less, determined that the link was definitive.

“After reviewing the medical literature on [repetitive head injuries] and CTE… we have the highest confidence in the conclusion that RHI causes CTE. We encourage the medical, scientific and public health communities to now act under the premise of a causal relationship and take immediate action to prevent CTE, minimise risk, and develop therapeutics to slow or stop disease progression,” wrote the authors, which included New Zealanders Sir Richard Faull, Helen Murray and Maurice Curtis, head of anatomy and medical imaging at the University of Auckland.

The Twitterverse jumped on board.

In press calls that day, Dr Chris Nowinski, head of the Concussion Legacy Foundation, said: “Sport governing bodies should acknowledge that head impacts cause CTE and they should not mislead the public on CTE causation while athletes die, and families are destroyed, by this terrible disease.”

It felt like a watershed moment for sport, its Big Tobacco = lung cancer moment. But instead the reaction in the medical science community has been lukewarm, and less than tepid in Big Sport.

Critics say that the paper’s conclusions are disingenuous because the relationship between CTE pathology and outcomes remains to be established and that the research used the Bradford Hill criteria to determine the link, which are a handy set of broad brushes but cannot cannot paint the full picture.

One who believes the link has been oversold is world-leading biomechanist Patria Hume of AUT.

“I do believe in the precautionary principle and from a biomechanics perspective I can’t see how damaging your brain in any way is good for you in the short or long term.  However when the question is about whether there is strong evidence for cause and effect, as a scientist I have to say there is not yet,” she says.

“It’s good that these issues are out there and we are discussing them, but in terms of the causal link, unfortunately I just don’t see the evidence.”

Hume says that by and large, the Bradford Hill paper is a strong piece of work but in discussions with other people in the field, their problem is the summary, which makes too big a leap from the content of the paper.

She says that another piece of work by Murray, a former New Zealand ice hockey captain turned neuroscientist, did a fantastic job of highlighting the gaps in CTE knowledge as it applied to sport. Murray’s summary stated that we “need more comparative studies that investigate a wide range of pathologies and how they differ between CTE, Alzheimer’s disease and normal ageing”.

Curtis, one of the paper’s authors, says the Bradford Hill criteria measure eight different factors, including strength of association (in this case between RHIs and CTE), consistency in studies, specificity, plausibility, coherence and the ability to replicate in experiments with animal models.

“It’s not like there’s a magic number [where correlation turns to causation], but there’s strong evidence of all eight,” he says, citing 15 years of intense study into CTE which he says has conclusively different pathology to other neurodegenerative diseases like Parkinson’s and Alzheimer’s.

“We’re not just seeing this in one brain bank. This is not just the work of one neurologist. It’s not just happening in one sport. We’re seeing this in brain banks all over the world.”

Hume’s call for caution when assessing causation between sports injuries and CTE is not new. An oft-cited paper in The Lancet co-authored by renowned neuroscientist Dr Willie Stewart from 2019 states that, “contrary to common perception, the clinical syndrome of CTE has not yet been fully defined, its prevalence is unknown, and the neuropathological diagnostic criteria are no more than preliminary”. It warned of the potentially “dire” consequences of misrepresenting CTE for those individuals who might have treatable conditions but are led to believe they are doomed to a life of neurodegeneration.

On the other side of the coin is the potentially more persuasive argument that failure to recognise the obvious – that RHIs in sport can lead to brain disease – and the willingness of Big Sport to hide behind the skirts of the scientific method is likely to contribute to hundreds and potentially thousands of needless deaths.

It feeds into the narrative that Big Sport is now playing the role of Big Tobacco, which exploited the “uncertainty” of the scientific method to flood the market with junk science and obfuscation for 30 years.

New Zealand Rugby senior scientist Ken Quarrie says that is not the case with rugby. He says while Big Tobacco deliberately deceived, rugby has proceeded on the assumption there is a compelling link.

“We want to know and understand what the evidence is”, he said. “We appreciate that with claims about causality with respect to a new health condition there will be uncertainties and, to the extent that people have different views on the scope and quality of the evidence, there are likely to be controversies about what actions should be taken with respect to managing risks.

“NZ Rugby will continue to act in accordance with the best evidence available, and our general approach is to err on the side of caution.”

Quarrie says that the research he is doing as an organisation is designed to address the question of the impact of playing high-level rugby on long-term health?

“Examining rates of neurodegenerative diseases among former players in comparison to the wider population is a key part of that,” he says.

The timing of Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy, the paper in question, is important, coming as it does against the backdrop of a class-action lawsuit by former players against World Rugby and several national unions, and the instability within the influential Concussion in Sport Group (CISG).

For years much of Big Sport – a catch-all term to refer to large billion-dollar sporting bodies like Fifa, the IOC, the NFL and World Rugby – have been happy to accept the findings of the CISG, whose consensus statement has refused to make a definitive link between RHIs and CTE.

However that group was rocked and some would argue discredited in the wake of its chairman Paul McCrory being forced to resign over a plagiarism scandal (his work is also under investigation by the AFL, for whom he worked in a medical advisory role, and the Australian Health Practitioner Regulation Agency).

The group has been unable to meet during the pandemic, but does so again in Amsterdam next month. It is under pressure to provide more meat on the bones of its consensus statement regarding the potential long-term effects of head injuries on athletes.

At the same time, World Rugby, the Rugby Football Union and Wales Rugby are facing a class action lawsuit from a number of former players, including All Blacks prop Carl Hayman and England’s World Cup-winning hooker Steve Thompson, who argue they were not sufficiently forewarned or protected from the dangers of repetitive head injuries.

When asked whether contact sports are now confronted with a public health crisis, Maurice Curtis says he would be reluctant to use that term, but adds: “I don’t want to shy away from the fact this is a serious matter”.

While NZR’s exposure to risk is mitigated by ACC legislation and its no-fault scheme, if it’s established that CTE is an industrial disease it will have a significant impact on sport around the world, with regards to obligations around workplace safety.

“The point here is not to bash any sport,” Curtis says. “The aim is to provide information and research that will help identify and reduce the problems.

“The last thing a 55-year-old ex-rugby player who might have used alcohol… that is suffering from a brain disease needs to hear is that they’ve brought it upon themselves,” he continues. “It’s about helping people be able to lead the best life they can.

“We don’t want to ‘stop’ anything, because there’s huge benefits in playing sports.”

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