About 74.5% of former National Football League players who died between 2008 and 2023 had chronic traumatic encephalopathy, or CTE, according to a Boston University-led estimate published October 28, 2026, in JAMA Network Open. Researchers put the figure at nearly 75% after adjusting for the fact that players who donate their brains are more likely to have had symptoms.
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The estimate covers only men who have already died. It says nothing direct about living retirees or current players.
The study was led by Julia Gallini, a doctoral candidate at the BU School of Public Health, with senior author Yorghos Tripodis, a professor of biostatistics there. Mass General Brigham and the Concussion and CTE Foundation collaborated. As the Insurance Journal report and the university’s own announcement describe, the team combined brain bank records with the National Death Index to cover all 2,362 NFL players who died in the period, of whom 396 had donated their brains and 1,966 had not.
The brain bank sample and the 94 percent donor result
Among 387 donors with known CTE status, 362 had some degree of CTE neuropathology, about 94%. A figure like that cannot be applied to the whole league, because families often donate after a player had memory trouble, mood changes or other symptoms. The Boston University release says former players with cognitive symptoms were about five times more likely to have their brains donated.
The researchers used that ratio to adjust the donor rate downward to the population estimate. The JAMA Network Open abstract reports 74.5% with a 95% confidence interval of 69.6% to 78.3%, and a more conservative lower-bound estimate of 63.7%. It also reports that 27.2% of the players had a history of dementia during life.
Selection bias and how this estimate differs from earlier ranges
An earlier study from the same group had estimated that between 25% and 98% of former NFL players who died from 2016 to 2021 had CTE. The wide range reflected uncertainty over how representative brain donors were. The new design narrows the interval by comparing donors with nondonors on cognitive symptoms, age at death, position and years played, rather than treating the donor sample as the whole league.
The gap between the 94% donor rate and the 74.5% adjusted rate is the heart of the paper. If donation were unrelated to symptoms, the two figures would match. The authors instead treat donor status as a biased filter and correct for it, and the conservative 63.7% lower bound shows how much the answer moves when the correction is made more cautiously.
Gallini said a precise estimate helps define the scale of the problem and informs priorities for the medical needs of this community. She noted that CTE is found in less than 1% of donors to community brain banks in the U.S., Australia, Austria and Brazil, a comparison that gives the NFL number its weight. Tripodis acknowledged that the findings may cause concern for living players and their families.
The legal and financial backdrop is long. The NFL agreed in 2013 to a $765 million settlement with retired players over claims it failed to share what it knew about head trauma, and in 2018 the NHL reached a $19 million settlement with more than 300 retired players, according to Insurance Journal. The new estimate arrives into that history with a sharper number than the 25% to 98% range that preceded it, though it still describes a group defined by its death dates, not today’s rosters.
What CTE pathology does and does not mean for living players
CTE can only be definitively diagnosed after death, and not everyone with CTE neuropathology develops symptoms, especially in early-stage disease. Earlier research found NFL players develop dementia at about four times the population rate. MedicineNet’s summary notes that 362 of 387 studied brains showed CTE-associated damage and that players with cognitive problems are about five times more likely to donate. The estimate depends on how well that selection ratio holds, which is why the researchers publish a lower bound beside the main number.
Matt Hasselbeck, an 18-year NFL veteran and ambassador for the DIAGNOSE CTE study, said it is hard to learn what the players who built the game have suffered through. Insurance Journal reported that the NFL said it continues to implement strategies to reduce concussions and head impacts, and that the NFL Players Association called such research critical to understanding football’s long-term effects. In CBS News coverage, the league pointed to equipment such as Guardian Caps and rule changes, and Patriots coach Mike Vrabel, a former linebacker, said players knew what the risks were.
The study leaves one practical gap open. Because diagnosis is possible only at autopsy, no one can yet tell a retired player whether he is among the roughly three in four. Gallini said the estimate argues for more effort to diagnose CTE during life and treat its symptoms.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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