Number & Strength of Head Impacts Drive CTE Risk in Football

Is the number of concussions suffered by a football player related to the chance of acquiring chronic traumatic encephalopathy (CTE)? Scientists discovered that the number of documented concussions alone was not connected with CTE risk in a new analysis of 631 deceased football players, the largest CTE study to yet. Instead, the probabilities of developing CTE among football players were related to both the number of head blows they experienced and the severity of the head impacts.
The report was published in Nature Communications by researchers from Mass General Brigham, Harvard Medical School, and Boston University (BU). It used an innovative new tool called a positional exposure matrix (PEM) to combine data from 34 different studies in order to quantify the quantity and severity of head impacts suffered by football players across their careers.

“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 Jesse Mez, MD, MS, 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 Dan Daneshvar, MD, Ph.D., 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.”

Based on the levels and positions athletes played during their football careers, the researchers utilized the novel PEM tool to estimate the cumulative amount of head impacts and the cumulative linear and rotational accelerations associated with those impacts. The researchers discovered that cumulative repetitive head impact (RHI) exposure was linked to CTE status, severity, and pathologic load in football players. Furthermore, the study discovered that models based on impact intensity were better at predicting CTE status and severity than models based just on period of play or number of strikes to the head.

The PEM is a great tool that academics can use to better studies on football risk factors. Researchers could employ the PEM in future studies to look at other potential impacts of RHI exposure other than CTE to acquire a better knowledge of the exact 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 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.”

A limitation of the study is that it utilized a convenience sample of football-playing brain donors who tended to have higher exposure to RHI than the general population of football players. However, a substantial number of donors had lower exposures, so the findings can still be extrapolated to most football players.

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