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Further light shed on CTE risk

Cumulative effect of head impacts, and strength of those impacts, are crucial in raising risk



Further evidence has emerged around the cumulative effect of head impacts in raising risk of chronic traumatic encephalopathy (CTE). 

The largest CTE study to date, involving 631 deceased football players, has revealed that their odds of developing the neurodegenerative disease were related to both how many head impacts they received and how hard the head impacts were.

It used an innovative new tool called a positional exposure matrix (PEM) that synthesised data from 34 independent studies to estimate the number and severity of football players’ head impacts over their careers.

And the study, by researchers at Mass General Brigham, Harvard Medical School, and Boston University, adds further to evidence that CTE risk cannot just be measured through the number of diagnosed concussions. 

“These results provide added evidence that repeated non-concussive head injuries are a major driver of CTE pathology rather than symptomatic concussions, as the medical and lay literature often suggests,” said study senior author Dr Jesse Mez, associate professor at the BU Chobanian and Avedisian School of Medicine and co-director of clinical research at the BU CTE Center.

The new data could provide football with a playbook to prevent CTE in current and future players, according to researchers.

“This study suggests that we could reduce CTE risk through changes to how football players practice and play,” said study lead author Dr Dan Daneshvar, assistant professor at Harvard Medical School and physician at Mass General Brigham affiliate Spaulding Rehabilitation. 

“If we cut both the number of head impacts and the force of those hits in practice and games, we could lower the odds that athletes develop CTE.”

The researchers used the new PEM tool to estimate the cumulative number of head impacts, and the cumulative linear and rotational accelerations associated with those impacts, based on the levels and positions athletes played throughout their football career. 

The study found that cumulative repetitive head impact (RHI) exposure was associated with CTE status, CTE severity, and pathologic burden in the football players. 

Additionally, the study found that models using the intensity of impacts were better at predicting CTE status and severity than models using duration of play or number of hits to the head alone.

The PEM is a valuable tool that researchers can utilise to improve studies on risks of football play. By using the PEM in future studies, researchers could look at other potential effects of RHI exposure beyond CTE to gain a better understanding of the specific types of RHI that are most likely to cause these problems.

“Although this study was limited to football players, it also provides insight into the impact characteristics most responsible for CTE pathology outside of football, because your brain doesn’t care what hits it,” said Dr Daneshvar. 

“The finding that estimated lifetime force was related to CTE in football players likely holds true for other contact sports, military exposure, or domestic violence.”