BOSTON (WHDH) - A new study led by researchers at Boston University estimates that nearly 75% of all NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) neuropathology.
CTE is a neurodegenerative disease that has been diagnosed in people with substantial exposure to repetitive head impacts. It can only be diagnosed after a person’s death.
The study, a collaboration among researches from Boston University, Mass General Brigham (MGB) and the Concussion & CTE Foundation, built on the findings from an August 2026 study that estimated 25% to 98% of former NFL players who died between 2016 and 2021 had CTE.
Boston University said the wide range reflected uncertainty about how representative brain donors were of the overall NFL population. It said brain donors are more likely to have symptoms believed to be related to CTE, a concept known as selection bias.
For the most recent study, researchers analyzed that selection bias to estimate the prevalence of CTE in players they didn’t directly study. “Among the 387 deceased NFL players that were studied, 362 (94%) had some degree of CTE neuropathology. Researchers then studied available records of death certificates from the National Death Index for all 2,362 NFL players from this era, which included data on how many died of neurodegenerative disease and had dementia,” Boston University said.
Researchers also analyzed cognitive symptoms, age at death, position, and years played in the NFL. From that analysis, they reestimated that former players with cognitive symptoms were about five times more likely to have their brains donated than those without symptoms. Researchers used that ratio to adjust the 94% prevalance of CTE to an overall estimate of 74.5%, Boston University said.
“It’s hard to learn what the guys who built the game have suffered through,” said Matt Hasselbeck, an 18-year NFL veteran who serves as the ambassador for the DIAGNOSE CTE study. “I’m looking at this like getting a scouting report. Now that we know what we’re up against, we have a better chance of winning. I can’t take back the hits I took, but I can sign up for research and do whatever I can to help the scientists so they can find a cure in my lifetime. 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.”
New England Patriots Head Coach Mike Vrabel spoke about the risks of playing football Wednesday.
“I knew what the risks were that your kids are going to have to see, maybe be knocked down on the field and laying unconcious, or getting another surgery, or breaking your arm, breaking your leg,” he said.
Researchers stress that this study does not predict how many living former NFL players have the disease, or how many active NFL players are impacted.
All former athletes, veterans, and anyone concerned about CTE can access support through the Concussion & CTE Foundation HelpLine.
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