At least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, or CTE, according to a new study that provides one of the clearest estimates yet of the brain disease among former professional football players. Researchers from Mass General Brigham, Boston University and the Concussion & CTE Foundation published the findings Tuesday in The BMJ after examining the brains of deceased former players.
Researchers identified 878 former NFL players who died during the six-year period. Of those, 235 had donated their brains for examination, and 215 — about 91% — showed evidence of CTE. Because people who experienced neurological problems may be more likely to donate their brains, researchers did not consider the 91% figure representative of all former players. Instead, they calculated a conservative minimum prevalence of 24.5%, while acknowledging that the actual rate could be substantially higher.
CTE is a progressive neurodegenerative disease associated with repeated blows or other impacts to the head. It can currently be confirmed only after death through examination of brain tissue. The study also found a strong relationship between advanced CTE and dementia: 61.3% of players with CTE who donated their brains met clinical criteria for dementia, while more than 90% of those with the most severe, Stage 4 disease had dementia.
The findings do not establish how many living former NFL players have CTE, nor do they mean that one-quarter of current players have the disease. Researchers also noted that many of the repeated head impacts associated with CTE likely occurred before players reached the NFL, including during youth, high school and college football. The study’s authors said reducing cumulative exposure to head impacts, rather than focusing only on diagnosed concussions, remains important in efforts to lower long-term risk.
The study adds to growing evidence linking prolonged exposure to head impacts with neurological disease among football players. Researchers say the results underscore the need for continued efforts to limit unnecessary contact at every level of the sport while improving evaluation and treatment for former athletes experiencing cognitive, behavioral or mood-related symptoms.
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