CTE Found in Nearly 75% of Deceased NFL Players in New Study

Nearly 75% of NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) pathology, according to a Boston University-led study that sought to address a key weakness in earlier estimates: donated brains may not represent all former players who died.

The result adds to evidence linking repeated head impacts with CTE, but its scope is specific. It describes findings after death among former players; it does not estimate how many living former players or active players have the condition. That distinction matters because CTE can be definitively diagnosed only after death.

A broader group of deceased players

The study examined 2,362 cases. Researchers combined data from 396 players who donated their brains with National Death Index records for 1,966 deceased players who did not donate. The work, conducted by researchers at Boston University, Mass General Brigham and the Concussion & CTE Foundation, was published in JAMA Network Open.

Including people who had not donated their brains was intended to address selection bias. Brain donation is more likely among families of players whose symptoms raised concerns about CTE. If researchers rely only on donated brains, the resulting share may overstate how common the pathology was among all deceased players.

An earlier study from the same research group estimated that between 25% and 98% of former NFL players who died between 2016 and 2021 had CTE. The wide interval reflected uncertainty over how well brain donors represented the wider group. The newer analysis expands the evidence base and produces a more precise estimate, according to the researchers.

Even with the larger set of cases, the estimate answers a narrow question: how often CTE pathology was found among players who had died during the period studied. It cannot establish prevalence among living players, and it does not show that every person with the pathology experienced symptoms.

Pathology and symptoms are different measures

CTE is a neurodegenerative disease diagnosed in people with substantial exposure to repeated head impacts. Researchers cautioned that pathology does not necessarily lead to noticeable illness, especially in early-stage cases. Among people who do develop symptoms, cognitive impairment, behavioral changes and dementia are among the signs described in the study coverage.

That gap between tissue findings and symptoms complicates efforts to interpret the estimate for families, players and health professionals. A high rate of pathology in deceased players signals a substantial burden in the group studied, while leaving open how many people had symptoms, how severe those symptoms were, and how they changed over time.

Lead author Julia Gallini, a PhD candidate at Boston University School of Public Health, said the estimate can help clarify the scale of the problem and inform priorities for potential medical needs. “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,” she said.

The comparison with community brain-bank donors offers context, but it does not make the groups equivalent. Their exposure histories differ, and the study’s estimate applies to deceased NFL players rather than to people generally.

Evidence on the wider health burden

The article also cites earlier research indicating that NFL players develop dementia at four times the rate of the population. A separate study published that summer in the British Medical Journal reported confirmed CTE in 215 of 235 athletes whose brains underwent postmortem neurological examinations. Those figures come from different research samples and methods, so they should be read as related evidence rather than as a single combined estimate.

The NFL said in statements to ESPN that it continues to use strategies intended to reduce concussions and head impacts. The NFL Players Association described the research as critical to improving understanding of football’s long-term effects. Matt Hasselbeck, an 18-year NFL veteran and ambassador for the DIAGNOSE CTE study, said, “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.”

For former players and their families, the findings sharpen the case for continued work on symptoms, care and diagnosis during life. For the sport, the central question is how to reduce exposure to repeated impacts and determine whether changes lower long-term harm. The study measures pathology after death; answers about living players and the effects of prevention efforts require different evidence.