Nearly 75% of ex-NFL players who died from 2008-2023 had CTE, study finds

Nearly 75% of NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, or CTE, a new study led by Boston University researchers finds.

CTE is a degenerative brain disease that is found in people who have suffered repeated blows to the head. It can only be definitively diagnosed after death. CTE has been discovered in football players as well as other athletes, first responders and military members.

The study published in JAMA Network Open shows how CTE, rarely seen in the general population, is far more common among deceased NFL players, lead author Julia Gallini said in a statement.

"With CTE consistently found in less than 1% of donors to community brain banks, an estimated 75% prevalence among NFL players who died over a 16-year period is concerning, and suggests we need to increase efforts to support families, diagnose CTE during life, and treat CTE-related symptoms," Gallini said.

CTE study findings

B.U. said the new findings build on a study released in August, which estimated that anywhere from 25% and 98% of ex-NFL players who died between 2016 and 2021 had CTE. 

"The wide range reflected uncertainty about how representative brain donors were of the overall NFL population," B.U. said in a statement. "Brain donors are more likely to have symptoms believed to be related to CTE, a concept known as selection bias."  

In the new study, 362 of 387 deceased ex-players were found to have some form of CTE. But to counter the selection bias, researchers factored in that former NFL players with cognitive symptoms were five times more likely to have their brains donated to science.

"They used this estimated selection ratio to adjust the 94% prevalence of CTE observed among brain donors to an overall estimate of 74.5%," B.U. said.   

The authors noted that the study only involved NFL players who have died and does not predict how many living former or active players might have CTE.  

"It's hard to learn what the guys who built the game have suffered through," former NFL quarterback Matt Hasselbeck, an ambassador for the study, said in a statement. "We have to learn from this data to make the game safer, because we can't accept these numbers for the next generation of players."  

NFL and NFLPA respond to CTE study

The NFL said in a statement that it "continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts." It pointed toward the introduction of better equipment like Guardian Caps and rule changes designed to keep players safe.

"The NFL remains committed to ensuring that the NFL community has access to a robust - and expanding - set of resources to enhance their physical and mental wellbeing," the NFL said. "We encourage former players to utilize these resources to identify and seek treatment when they are concerned about their health."

The NFL Players Association said the study is one of many that are "critical" to understanding the long-term health impacts of football. 

"The NFLPA remains committed to supporting scientific research, investing in resources that aid players' physical and mental well-being, and expanding access to care so that they can experience improved health outcomes during and after their playing careers," the union said.