About three of every four former National Football League players who died between 2008 and 2023 likely had chronic traumatic encephalopathy, or CTE, according to a Boston University study published October 28, 2026, in JAMA Network Open. The researchers put the bias-adjusted prevalence at 74.5% among the 2,362 former players who died during that 16-year period. News coverage describes it as the first population-level estimate of CTE among deceased NFL players.
CTE is a degenerative brain disease associated with repeated head impacts, and it can be definitively diagnosed only by examining the brain after death. That has long made its true frequency hard to measure. Earlier research relied on brains donated to research banks, and families of players who showed symptoms in life are more likely to donate. A widely cited 2017 Boston University analysis found CTE in 99% of donated NFL players’ brains, a figure critics argued was inflated by that selection effect.
The new study, titled “Bias-Adjusted Prevalence of Chronic Traumatic Encephalopathy Among Deceased National Football League Players,” tries to correct for donation bias. According to reporting by The Boston Globe and Science News, the team started with nearly 400 former players whose brains were in Boston University’s brain bank. About 94% of those donors had CTE. The researchers then used death certificate data from the National Death Index on every former player who died during the study period. They also considered records of dementia and cognitive symptoms, along with age at death, position played, and years in the league. Players with cognitive symptoms were about five times more likely to have their brains donated, and the team adjusted for that difference when extending its estimate to players whose brains were never examined.
ABC News reported that the researchers also estimated 27.2% of the former players had dementia during their lifetimes, a figure the authors said likely understates the true rate. For comparison, the Globe reported that CTE prevalence in the general population is estimated at under 1%. It added that former NFL players may be roughly four times more likely than the general population to develop dementia and other neurodegenerative diseases.
The authors acknowledge that no adjustment can remove every source of bias. Senior author Yorghos Tripodis, a Boston University biostatistics professor, told ABC News that the estimate did not drop below 60% even under very conservative assumptions. Lead author Julia Gallini, a doctoral candidate at the Boston University School of Public Health, cautioned in the Globe that the result is an estimate for deceased former players and does not predict the share of current players who will develop CTE. Not every case of CTE produces symptoms, and symptoms tend to appear in later stages of the disease. The players’ head impacts also often began in youth, high school, or college football rather than in the pros, according to co-author Daniel Daneshvar of Mass General Brigham.
The study refines an August 2026 analysis by several of the same researchers. That earlier work, which Insurance Journal reported was led by Daneshvar, examined former players who died between 2016 and 2021. It set a conservative minimum of about one in four with CTE. ABC News reported that the earlier study’s plausible range ran from 25% to 98%, and Tripodis said the team wanted to narrow that range. Dr. Ramon Diaz-Arrastia of the University of Pennsylvania, who was not involved in the study, told the Globe it is a paper the field “has been waiting on for a long time.”
The NFL pointed to the statement it issued after the August study, saying it continually works to make the game safer and remains committed to providing resources for players’ well-being. The NFL Players Association told the Globe that such studies are critical to understanding football’s long-term effects.
For employers and insurers, the findings bear on the cumulative-trauma and occupational-disease claims that former professional athletes have long pursued, including in California’s workers’ compensation system. A credible population-level estimate of brain disease among NFL veterans could figure in how such claims are evaluated and reserved, although the study itself does not address compensation or causation in any individual case. The researchers’ emphasis on exposure beginning in youth and amateur football may also interest carriers that write coverage for schools, colleges, and youth sports organizations, as well as other contact-sport employers.