In a landmark move, the US National Institutes of Health (NIH), the world’s largest biomedical research agency, has formally acknowledged a clear causal link between repeated blows to the head and the neurodegenerative disease chronic traumatic encephalopathy (CTE), suffered by a growing number of sportsmen, among others, worldwide.
The move, following a several studies showing a link between CTE and contact sports, could spark changes to contact sports worldwide, especially relating to youths, as is the intention of leading scientists and medical experts who prompted the new US guidelines, notes Medical Brief.
The Guardian reports that the decision to rewrite its official guidance on CTE has been described by campaign groups as a tipping point in the debate about the risks of playing collision sports. In the NIH’s view, research to date suggests the link between repeated traumatic brain injury and CTE is clear and unequivocal.
That position is at odds with the one held by the Concussion in Sport Group (CISG), which is supported by Fifa, World Rugby and the IOC, among others. The concussion consensus documents published by CISG have consistently played down the connection between CTE and brain injuries from sport, a position used by many sports federations as they defend themselves against legal challenges and calls to reform.
The NIH’s change in guidance was made after a group of 41 leading scientists, doctors and epidemiologists co-signed a letter to the National Institute of Neurological Disorders and Stroke (Ninds). The letter cited a recent review of the research into CTE, published in July in the Frontiers in Neurology journal, which established a clear causal link with the kinds of recurrent brain injuries suffered by abuse victims, soldiers and sportspeople, in particular.
There has been evidence this is the case since the disease was first recognised in the 1950s with the director of Ninds saying the causal link was “pretty clear” in 2014, but their official guidance had not reflected that until now.
The change brings the NIH into line with the US Centres for Disease Control and Prevention (CDC), which stated in its advice in 2019: “Most research suggests that CTE is caused in part by exposure to repeated traumatic brain injuries.” It means two of the leading independent medical research bodies in the world are in agreement on the causes of CTE.
It remains be seen whether CISG’s next concussion consensus will reflect that. The group is holding a conference in Amsterdam today and tomorrow to draft the latest iteration of the consensus, which will be published early next year.
CISG is already under increased scrutiny after its chair, and lead author, Dr Paul McCrory, resigned this year when it was alleged there were multiple instances of plagiarism in his own work. At the time McCrory was quoted on Retraction Watch apologising, saying his failure to attribute was “not deliberate or intentional”.
“Now that causation has been established, the world has a tremendous opportunity to prevent future cases of CTE,” said a spokesperson for the not-for-profit group, the Concussion Legacy Foundation. “The only known cause of CTE is an environmental exposure, and in most cases a choice – the choice to play contact sports.
“Our goal is to reform all youth sports so they no longer include preventable repetitive head impacts before age 14 – no heading in soccer, no tackling in (American) football and rugby.
“This change, combined with logical limits to repeated head impacts in sports for people over 14 (such as no hitting in football/rugby practice and strict limits on headers in practice) would be expected to prevent the vast majority of future CTE cases.”
The landmark development comes as scientists increase calls for sporting codes to minimise head impacts and injuries after another study recently connected contact sport participation to a higher chance of developing a degenerative brain disorder.
Cosmos reports that the research published in the Journal of Neurology Neurosurgery & Psychiatry found risk of neurodegenerative disorder among Scotland’s former international rugby union players was more than double that of the wider population.
Risk varied based on the type of disorder: the chance of dementia was twice as high as among the general public. Motor neurone disease was 15 times higher.
The research group from Glasgow University and Queen Elizabeth University Hospital previously found an increased risk of neurodegenerative disease among Scottish association football (soccer) players, and a greater likelihood of death from dementia.
It adds to an increasing body of international research into the effect of high-contact sports particularly football codes – on the brain.
Earlier this year, research from La Trobe University and Sydney University found over 95% of athletes whose brains were donated to the Australian Sports Brain Bank had signs of neurodegeneration.
Most of these players had participated in football codes.
Bank of brain injury knowledge continues to expand
Among the findings, the researchers working under the oversight of senior author William Stewart found consistencies with studies of former National (American) Football League and professional soccer players.
Given a largely amateur playing contingent represents Scotland internationally, the researchers suggest their findings are the “first demonstration that high neurodegenerative disease risk is not a phenomenon exclusive to professional athletes”.
Dr Helen Murray from the University of Auckland’s Centre for Brain Research, which established New Zealand’s own sports brain bank, says the study extends the knowledge of which brain disorders may eventuate from repeated brain injury.
“Chronic Traumatic Encephalopathy (CTE) is the most widely known brain pathology linked repetitive head injury in sport,” Murray says.
“However, this study reinforces the idea that head injury risk is not limited to CTE, and former contact-sport athletes should be monitored for all types of dementia. Every type of dementia is devastating.”
A study published in July by researchers from the US, Australia, New Zealand, Brazil and the UK supported a connection between repeated head injuries and CTE.
Alan Pearce, an associate professor in exercise neuroscience from La Trobe University who contributed to the analysis of brains donated to Australia’s sports brain bank, said the findings support sports codes taking more action to minimise the risk of brain damage in participants.
“We need a concerted effort to change how we approach these sports in not only concussion management but also in reducing exposure to adult athletes,” Pearce says.
“That’s as well as modifying contact sports for junior players – children and young adolescents – up to the age of 14 years.”
The most recent data from the Australian Institute for Health and Welfare found concussions account for most sports-related head injuries among people under the age of 65.
The proportion of these head injuries during sports participation that led to hospitalisation was highest among children aged 15-19 (8.98% of hospitalisation causes).
frontiers of science
Cosmos – risk of brain disorder double in rugby players
Journal of Neurology Neurosurgery and Psychiatry – Football and Dementia – Understanding the risk
See more from MedicalBrief archives:
Retractions, plagiarism concerns over dozens of articles by concussion expert
Professional rugby players’ brains can be affected in single season
US football: Best route to reduced concussion is in practice, not game play
England rugby CEO says lawsuit threat over concussion can drive change