In a statement Wednesday, the Concussion in Sport Group, a panel of the world’s leading experts on concussion and head trauma, stopped short of definitively linking the brain disease CTE with repeated head trauma.
CTE, a brain disease diagnosed after death through autopsy, has gained notoriety for its prominence among former NFL players who have struggled with symptoms like dementia and suicide. The US Centers for Disease Control and Prevention says “the research to date suggests that CTE is caused in part by repeated traumatic brain injuries, including concussions, and repeated hits to the head, called subconcussive head impacts.”
However, in the sixth and latest International Consensus Statement on Concussion in Sport, published Wednesday in the British Journal of Sports Medicine, the concussion group says “It is reasonable to consider extensive exposure to repetitive head impacts, such as that experienced by some professional athletes, as potentially associated with the development of the specific neuropathology” described as CTE.
The consensus statement is used as guidance for protocol for many international sporting leagues, including soccer’s FIFA and the International Olympic Committee.
“The CISG statement on CTE, and their refusal to clearly acknowledge a causal relationship between contact sports participation and CTE, is a danger to the public,” Chris Nowinski, co-founder and CEO of the Concussion Legacy Foundation, said in a statement to CNN. “On the question of CTE causation, we urge the public to listen to the statements of independent organizations like the National Institutes of Health (USA), Centers for Disease Control and Prevention (USA), and National Health Service (UK), all of whom have concluded that CTE is caused by repeated traumatic brain injuries.”
Study finds that nearly 92% of former NFL players have brain disease
The Concussion Legacy Foundation and Boston University’s CTE Center have spearheaded much of the research around the condition in the United States. The most recent research from the BU/CTE Center found that nearly 92% of 376 former NFL players who were studied were diagnosed with the brain disease, which can cause changes to the brain and manifest in a variety of symptoms including memory loss, confusion, aggression, depression and even suicidality. Research has found that severe cases of the disease to have progressed to dementia.
However, there is a potential bias in these numbers because the brains donated were probably submitted by relatives who noticed these symptoms in their family members when they were living.
The consensus statement noted that the review from the Concussion in Sport Group took over five years and was informed by 10 systematic reviews of the most current CTE studies but that many of “these studies of former athletes are not cohort studies that can examine causation or quantify risk and thus were not included in the systematic review.”
Cohort studies are used in epidemiology and follow groups of people with common characteristics over a long period of time, comparing them with a group that hasn’t had the same environmental exposure – in this case, repeated head trauma.
‘We have to act on what we know now’
“There are researchers out there who, rightfully so, want really strong data. We all should be striving for very strong evidence, but it’s very hard to come by in environmental exposure cases like this,” said neuroscientist Julie Stamm, a clinical assistant professor in the Department of Kinesiology at the University of Wisconsin-Madison who was not involved in the consensus statement.
She agreed that cohort studies will yield the best evidence regarding CTE, “but that’s going to take decades,” she said.
Dr. Nsini Umoh, program director of the National Institute of Neurological Disorders and Stroke, agreed that the data was strong regarding the relationship between repeated head trauma and CTE. She said her group, a division of the US National Institutes of Health, updated its own description of CTE to say it “is caused in part by repeated traumatic brain injuries.”
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“Based on the body of evidence, that’s what the research was suggesting,” said Umoh, who also was not involved in the consensus statement.
Stamm agreed that there was still much to understand about CTE. “Scientifically looking at it, yeah, we have so much to learn yet,“ but she worried how this position statement could be interpreted.
“It can be used by different organizations or individuals to say, ‘Oh, well, everything’s OK. They didn’t say there was a connection. So there’s not a connection,’ ” Stamm said.
“We have to act with what we know now,” she said. “And what we know now is pretty convincing.”