Study: Cumulative force of impacts — not concussions — predicts CTE

The largest study to date of chronic traumatic encephalopathy (CTE) found that cumulative force to the head — not diagnosed concussions — is the best predictor of future brain disease.

Why it matters: This could lead to a fundamental shift in head safety and injury prevention across sports, as focusing on concussions misses the point of how harmful an accumulation of subconcussive impacts can be.

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"We're now getting a better understanding of [not only what causes CTE, but what doesn't]. And in this case … concussions were basically noise."

Dr. Daniel Daneshvar, the study's lead author, to NYT

Details: The study, published Tuesday in the scientific journal Nature Communications, used data from football helmet sensors going back 20 years to estimate the cumulative impact of hits on 631 former football players who'd donated their brains to Boston University.

Data: Nature Communications; Table: Axios Visuals

By the numbers: As you can see above, each hit sustained by defensive and offensive linemen is less forceful than those sustained by players at other positions. But linemen experience by far the most total G-force of impact each season due to the sheer volume of hits.

• That cumulative impact — not isolated traumatic events — is why linemen are more likely to develop CTE than other players, according to the study.
• For example, a running back who played for 10 additional years is 11x more likely to develop CTE than one who played just two years of youth football. But a defensive lineman who played 10 additional years is 30x more likely due to the prevalence of subconcussive hits.

Yes, but: Such hits, and their impact, can be reduced. And some of that work has already begun.

• More players are wearing devices like the Q-Collar, which restricts blood flow from the head to provide extra cushioning around the brain. And the National Football League is recommending the expanded use of Guardian Caps to increase protection during practice and offseason training.
• Some coaches at the youth level are eliminating full-contact practices, and for years both USA Football and Pop Warner have limited or banned linemen from starting in a crouch to decrease head-to-head contact.
• Helmets have also become safer over the years as the NFL routinely funds research in helmet innovation. The NFL also now has position-specific helmets for linemen and quarterbacks.