In a move that will have ramifications for collision sports, the US National Institutes of Health has officially recognized a causal link between repeated blows to the head and the neurodegenerative disease chronic traumatic encephalopathy (CTE).
The NIH is the world’s largest biomedical research agency and the decision to rewrite their official guidelines on CTE was described by campaign groups as a turning point in the debate over the risks of playing collision sports. According to the NIH, the research to date shows that the causal relationship between repetitive traumatic brain injury and CTE is clear and unequivocal.
This position is at odds with the position of the Concussion in Sport Group, which is supported by FIFA, World Rugby and the IOC, among others. Consensus documents on concussion published by the CISG have consistently downplayed the link between CTE and brain injuries sustained in sports. The most recent, from 2017, states “no causal link has been established to date between CTE and concussions or exposure to contact sports,” a position that has been cited by multiple sports federations as they defend against both legal challenges and calls for reform.
The change in the NIH guidelines 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 cites a recent review of CTE research published in July in the journal Frontiers in Neurology that found a clear causal link to the types of repetitive brain injuries suffered by victims of violence, soldiers and athletes in particular. There has been evidence that this has been the case since the disease was first recognized in the 1950s, with the director of Ninds saying the cause-and-effect relationship was “pretty clear” in 2014, but their official guidance did not reflects this so far.
The change brings the NIH in line with the U.S. Centers for Disease Control and Prevention, which stated in a 2019 advisory: “Most research indicates that CTE is caused in part by exposure to repetitive traumatic brain injury.” This means that two of the world’s leading independent medical research organizations agree on the causes of CTE. It remains to be seen whether the next CISG consensus on concussion will reflect this. 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 has already come under increased scrutiny since its chairmanship and the lead author, Dr Paul McCrory, resigned earlier this year when it was alleged there were numerous instances of plagiarism in his own work. At the time, McCrory was quoted in Retraction Watch as apologizing, saying his failure to credit was “not intentional or deliberate.”
“Now that causation has been established, the world has a tremendous opportunity to prevent future cases of CTE,” said a spokesperson for the nonprofit Concussion Legacy Foundation. “The only known cause of CTE is environmental exposure and, in most cases, choice — the choice to play contact sports.
“Our aim is to reform all youth sports so that they no longer involve preventable repeated blows to the head before the age of 14 – no heading in football, no wrestling [American] football and rugby.
“This change, combined with logical restrictions on repeated head impacts in over 14 sports (such as no head impacts in football/rugby training and strict limits on head impacts in training) is expected to prevent the majority of future cases of CTE.”