A new study published in the British Medical Journal found that, at minimum, nearly a quarter of former NFL players who died between 2016 and 2021 had confirmed chronic traumatic encephalopathy (CTE) at death.
CTE is a neurodegenerative disease linked to repeated head impacts. The research adds to a growing body of evidence tying contact-sport head trauma to long-term brain disease, while highlighting how much about its true scope remains unknown.
CTE can only be diagnosed through post-mortem brain examination, which has made it difficult to estimate how common the disease actually is among former players.
To address that gap, researchers examined brain tissue donated by 338 former NFL players — out of 1,712 who died between 2008 and 2021 and had played at least one NFL game since 1949 — through the UNITE brain banks at Boston University's CTE Center, Mount Sinai and the UCSF Alzheimer's Disease Research Center.
Of the donated brains studied, 315, or 93.2%, showed evidence of CTE. Because donation is voluntary and skews toward families who suspected symptoms, researchers calculated a wide possible prevalence range for the full population of NFL decedents, between 18.5% and 98.7% overall, narrowing to between 24.5% and 97.7% for players who died from 2016 to 2021, when donation rates were highest.
Among the donors studied, nearly 31% had the most advanced form of the disease, stage IV CTE, and roughly 60% had been diagnosed with dementia by a study clinician. Players with stage IV CTE were significantly more likely to have shown dementia-like symptoms, including memory loss and cognitive decline — before death, with a 44% higher likelihood of a dementia diagnosis compared with donors with less advanced disease.
"This study is a sobering reminder that football carries real risks, and those risks can have lasting consequences for players and their families," the NFLPA said in a statement to ESPN. "It also reinforces one of the NFLPA's core priorities: improving player safety and supporting players throughout their lives, both during and after their careers.
"The findings should serve as a call to action across the entire football ecosystem. We all share a responsibility to advance research, improve access to care, develop better treatments, and support those affected by the long-term impacts of the game."
The study's authors, cited in the research, wrote that the findings indicate NFL players have a higher prevalence of CTE at death than has been shown in prior community-based studies, and that CTE severity is significantly linked to dementia among donors.
The authors cautioned that the retrospective, donation-based design limits how firmly the findings can be generalized, since not all former players who died during the study period were included and family recollections of symptoms may not always be precise.
