A leading figure in brain injury research, Dr Willie Stewart, has launched a scathing rebuke of a major study investigating head injury risks in rugby, suggesting that the findings may be compromised by conflicts of interest and lack of transparency.

Stewart, a consultant neuropathologist with a distinguished academic portfolio including honorary and adjunct professorships, questioned the recent findings from a collaboration between New Zealand Rugby (NZR), Otago University and World Rugby in an interview with Whakaata Māori.

In response, NZR said in a statement to the Herald it has been involved in “world-leading research” and both research papers had been peer-reviewed and published in “reputable academic journals.”

The criticised study – known as the ORCHID and championed by the NZR – this week was promoted as providing a measure of head impact forces in community rugby, comparing them to everyday physical activities and claiming that the majority of these forces are less than or equal to general exercise impacts, like running.

However, Stewart’s pointed critique slams what he says are shortfalls in the research, directly challenging the study’s integrity, and saying a lack of a peer review undermines the whole thing:

“There is good reason why research is peer-reviewed before communicated. While far from perfect, the peer review system is designed to ensure that the questions addressed are appropriate, the methods employed are robust and the results are discussed in a dispassionate and balanced way,” Stewart said.

NZR strongly reiterated in the statement to the Herald the two research papers had been peer-reviewed.

The Glasgow-based neuropathologist’s concerns extend to the methodologies and communications surrounding the research. His first target? A potential for bias in the data representation, “We might debate some of the methods used here, in particular the choice of thresholding which gives an artificially optimistic view of head acceleration events.”

The study breaks down the impact of the individual hits into G forces, claiming 86 per cent of knocks are about the same as a run.

Stewart goes on to assert that the study’s independence is questionable, as it was funded by World Rugby and involved several of its direct employees, a detail disclosed in the manuscript’s footnotes but contrary to the media release claims.

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He underscores the severity by stating: “This then raises questions as to why a global sporting organisation would make claims of independence of research works, which they clearly are not.”

Stewart’s criticisms come amid mounting legal pressures surrounding brain injuries in contact sports.

More than 400 rugby and football players, including former All Black prop Carl Hayman, who at 43 disclosed his battle with early-onset dementia, are suing the governing bodies of their sports as a result of health conditions in the years following their playing careers.

To add to the pile-on, Wednesday evening, the Royal College of Pathologists of Australasia (RCPA) confirmed a causal link between repeated head injuries and chronic traumatic encephalopathy (CTE), a brain condition leading to cognitive, mood and motor disorders, now seen in individuals as young as 20.

The RCPA is calling on governing bodies to take action on CTE through five action points, which include a recommendation that low or no-contact versions of sports are played by rangatahi under the age of 14.

A litany of sportspeople across all fields of contact sports have been diagnosed with CTE in recent years, including former NFL linebacker Junior Seau, Chris Benoit, a professional wrestler, and Dave Duerson, a former NFL defensive back.

According to a study published in the Journal of Neurosurgery, an estimated one in five (19 per cent) of people with CTE have died by suicide, including all three of the aforementioned.

New Zealand Rugby said in its research statement it has an “absolute commitment” to making the game as safe as possible and “reducing the risk of injury to our participants at all levels”.

It said the brain injury research came in the wake of other recent World Rugby commissioned research which claimed that playing rugby provided US$1.5 billion in preventative healthcare savings around the world, 30 per cent reductions in levels of childhood obesity, 15 per cent reduction in heart disease and 33 per cent reduction in mental illness amongst adults.

Stewart says there’s an urgent need for unbiased and scientifically rigorous research to protect athletes’ health, slamming the joint NZRU and World Rugby press release he suggests was parroted by media.

“Beyond this glaringly inappropriate claim of independence, the focus of the release presents, in essence, a positive spin on head acceleration forces in rugby.”

He raged over the report’s claim that head injuries in the sport are somehow the responsibility of bad technique by players.

“The paper includes no studies comparing rugby head acceleration events to those of running, skipping or roller coasters [despite saying they were just as bad for brain health], nor are any data provided to support the claim that the higher force acceleration events are due to bad technique.”

He reiterated his view the integrity of research in the area remains crucial for the future of the sport and the safety of its players.

In a statement, NZR said player welfare was “a major priority” and it was important to take “an evidence-based approach”.

“Part of that commitment involves actively contributing to scientific research which progresses the understanding of player safety in rugby, including head impacts.

“NZR has people involved in world-leading research and scientific integrity is always their priority. These two particular research papers have both been peer-reviewed and published in reputable academic journals.

“There is significant work happening at all levels of the game to continue to make it safer and we welcome contributions to this, as well as productive, robust discussion.”