In a move that will have ramifications for collision sports, the US National Institutes of Health has formally recognized a causal link between repeated blows to the head and the neurodegenerative disease chronic traumatic encephalopathy (CTE).
The NIH is the largest biomedical research agency in the world, and the decision to rewrite its official guidance on CTE has been described by campaign groups as a turning point in the debate about the risks of playing collision sports. In the NIH’s view, research to date suggests that the causal link between repetitive traumatic brain injury and CTE is clear and unequivocal.
That position is at odds with that of the Concussion in Sport Group, which is supported by Fifa, World Rugby and the IOC, among others. The concussion consensus documents published by the CISG have consistently downplayed the link between CTE and brain injuries sustained in sports. The latest, from 2017, says “to date, a cause and effect relationship between CTE and concussions or exposure to contact sports has not been established,” a position that has been cited by several sports federations as they defend themselves against both legal challenges and calls for reforms.
The NIH’s change in guidance was made after a group of 41 leading scientists, physicians and epidemiologists signed a letter to the National Institute of Neurological Disorders and Stroke (Ninds). The letter cited a recent review of the research on CTE, published in July in the journal Frontiers in Neurology, which established a clear causal link with the kind of recurrent brain damage that victims of abuse, soldiers and athletes in particular suffer. There has been evidence that this is the case since the disease was first recognized in the 1950s, and the director of Ninds said the causal link was “pretty clear” in 2014, but their official guidance had not reflected that until now.
The change brings the NIH in line with the US Centers for Disease Control and Prevention, which stated in its 2019 advisory: “Most research suggests that CTE is caused in part by exposure to repeated traumatic brain injuries.” This means that two of the leading independent medical research bodies in the world agree on the causes of CTE. It remains to be seen whether the CISG’s next concussion consensus will reflect that. The group is holding a conference in Amsterdam on Thursday and Friday to draft the latest iteration of the consensus, which will be published early next year.
The CISG is already under increased scrutiny after its chairman and lead author, Dr. Paul McCrory, resigned earlier this year when it was alleged that there were several instances of plagiarism in his own work. At the time, McCrory was quoted on Retraction Watch as apologizing and saying his lack of attribution 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 spokesman for the non-profit group 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 aim is to reform all youth sports so that they no longer include preventable repetitive head impacts before the age of 14 – no course in football, no tackling in [American] football and rugby.
“This change, combined with logical limits on repetitive head impacts in sports for people over 14 (such as no punches in soccer/rugby training and strict limits on head impacts in practice) is expected to prevent the vast majority of future CTE cases.”
