Questioning the evidence for repeated head impacts and chronic traumatic encephalopathy

A new study by Dr. Lauren Fortington of Edith Cowan University (ECU) in Perth, Australia, challenges existing knowledge about a new condition called chronic traumatic encephalopathy-neurpathological change (CTE-NC).

Concerns about CTE-NC have increased significantly in recent years, particularly among athletes who participate in contact sports such as American football, Australian rules football, rugby, ice hockey, martial arts, and boxing.

Dr. Fortington, an injury epidemiologist, along with an international team of researchers from a range of academic disciplines, questioned the methodology and findings of a high-profile 2022 article that claimed “compelling evidence of a causal link between repeated head impact (RHI) and CTE.”

“To say A leads to B, we first need to understand what A and B are. There is no scientific consensus on RHIs and CTE-NC – we don’t have a clear understanding of the burden and consequences, and we don’t have appropriate methods to accurately record them,” Dr. Fortington said.

Dr. Fortington said that even if there were already a scientific consensus on what constitutes RHI and CTE-NC, the application of these working definitions would still be insufficient to draw causal conclusions on the matter due to the inherent limitations of the study designs used to date.

“So, in our view, we have, on the one hand, weak definitions and inconsistent measurements of the burden of the presumed cause, and, on the other hand, a lack of consistency in determining the outcome because pathologists have had difficulty reaching agreement on the thresholds for CTE and how to reliably distinguish CTE from other diseases.

“And between exposure and outcome, from our perspective, it is not clear whether there is a clinical syndrome (a set of signs and symptoms) that distinguishes CTE from other health conditions that can occur in middle and old age.”

The results are published in the journal Sports medicine.

Although symptoms such as mood swings, confusion, disorientation and dizziness have been suspected, these problems have also been associated with a number of other diseases and age-related ailments.

“The question of whether CTE-NC or another yet-to-be-determined pathologic outcome is associated with clinical signs and symptoms in individuals exposed to brain trauma is a high priority question that remains to be answered,” noted Dr. Fortington.

Dr Ken Quarrie, Chief Scientist of the New Zealand Rugby Federation and co-author of the new publication, stressed the importance of maintaining clarity and objectivity in this ongoing debate.

“To help the public understand what is known and what is not, it is important that people recognize that this article has undergone a rigorous peer review process and has been published in a reputable journal.

“The polarized nature of the debate around CTE creates the risk that the facts will be misrepresented – whether downplayed or exaggerated. Our role as scientists is to ensure that we communicate the evidence accurately and responsibly,” said Dr. Quarrie.

“While work toward a clear consensus regarding RHI and CTE-NC is still ongoing, much is already being done to reduce sports injuries, not only among professional athletes but also at the societal level,” said Dr. Fortington.

“Until the results of several high-quality studies are published, the scientific community and all those who disseminate research results need to be more critical of claims about scientific impact in this field.”