A new study from researchers at Boston University estimates that about three in four NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, or CTE, the degenerative brain disease linked to repeated head impacts. The figure, 74.5%, is the highest estimate yet of how common the disease is among former players, and it is the first to try to account for every player who died in that period, not only the ones whose brains were donated for study.
The study was published on Wednesday, Oct. 28, in the peer-reviewed JAMA Network Open. It was a joint project of Boston University, Mass General Brigham and the Concussion & CTE Foundation, led by biostatistics PhD candidate Julia Gallini and professor Yorghos Tripodis. “I had to double-check the numbers,” Tripodis said.
How the researchers got to 75%
The starting point was the brain bank. Of 387 former NFL players whose brains were donated and examined, 362, or 93.5%, had some degree of CTE. Critics have long argued that number is inflated, because families who saw memory loss, mood changes or dementia in a former player are more likely to donate his brain.
To deal with that, the researchers pulled death records for all 2,362 former NFL players who died from January 2008 through December 2023, including the 1,966 whose brains were never donated. They compared donors and non-donors by cognitive symptoms, age at death, position and years in the league, and found that players with cognitive symptoms were about five times more likely to be donated. Adjusting the 93.5% rate for that bias produced the estimate of 74.5%, or roughly 1,760 of the 2,362 players. Even the most conservative version of the analysis put the figure at 63.7%.
For comparison, CTE has been found in fewer than 1% of the thousands of brains donated to community brain banks in the United States, Australia, Austria and Brazil. The players in the study spent an average of about five seasons in the league, and 41% of them were 80 or older when they died. The researchers also estimated that 27.2% had a history of dementia during their lives.
Our new study, published today in @JAMANetworkOpen, estimates that 75% of NFL players who died between 2008 and 2023 had CTE.
— Chris Nowinski, Ph.D. (@ChrisNowinski1) October 28, 2026
This is not a measure of all current or former players. It does not mean 75% of current players have CTE, and not everyone with CTE develops symptoms.
What the number does not say
The authors were careful about the limits. The estimate covers former players after death. It does not say how many living former players have CTE, and it says nothing directly about active players. CTE can only be confirmed after death, and not everyone with signs of the disease develops symptoms. “We don’t know that number,” Gallini said when asked about current players. “The magnitude of this number, though, is very concerning. It still tells us we need to be concerned about the risk of current players developing CTE.”
Chris Nowinski, a co-author and chief executive of the Concussion & CTE Foundation, said the main value of the study is that it answers the selection-bias argument that has been used to dismiss earlier brain-bank findings. “This study helps us understand exactly what we’re facing,” he said. The new paper builds on an August study by the same group, which estimated a range of 25% to 98% for players who died between 2016 and 2021. That range was so wide because nobody knew how representative the donors were.
The league and the union respond
The NFL answered with the same statement it issued after the August study. “The NFL continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts,” a league spokesperson said, adding that the league “remains committed to ensuring that the NFL community has access to a robust – and expanding – set of resources” for players’ physical and mental health and encouraging former players to use them. The league points to measures such as the padded Guardian Caps required in most contact practices since 2022, newer helmet models and the dynamic kickoff, which cuts down on high-speed collisions. Nowinski has argued that Guardian Caps will not protect against CTE.
The NFL Players Association called the study one of many that are “critical” to understanding the long-term effects of football and said it remains committed to research, care and “expanding access to care” for players during and after their careers. After the August study, the union emailed every player and agent, calling the findings “a sobering reminder that football carries serious risks” and “a call to action across the entire football ecosystem.” The league and the union are already working together on a separate health matter this season, a joint review of Jalen Hurts’ medical care.
Former players: a scouting report
Former Seahawks quarterback Matt Hasselbeck, who played 18 seasons and is an ambassador for a research study on diagnosing CTE in living people, said the numbers were hard to read. “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,” he said. “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.”
Hall of Fame defensive tackle Warren Sapp took a similar line. “We can attack CTE, we can END CTE,” he said in a video message. Boston College coach Bill O’Brien, a former head coach of the Texans, called the findings “very concerning” for the future of the sport.
Pro Football Hall of Famer Warren Sapp has a powerful message in response to a new @bu_cte study that estimates 75% of former NFL players who died between 2008 and 2023 had CTE.
— Concussion & CTE Foundation (@ConcussionCTEfn) October 28, 2026
It’s not a good number. But for Warren, it’s also a call to action.
The researchers stressed that many symptoms linked to CTE, including depression, anxiety, sleep problems and memory trouble, can also come from other conditions that can be treated, and urged former players with concerns to see a specialist in neurodegenerative disease. Previous research has found that former NFL players develop dementia at about four times the rate of the general population. Former players can get help through the union’s Former Players Department, the Professional Athletes Foundation and the league-funded NFL Life Line, which is available around the clock at 800-453-0078.
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