At minimum, nearly a quarter of all former National Football League (NFL) players who died from 2016 to 2021 had confirmed chronic traumatic encephalopathy (CTE) – a neurodegenerative disease linked to repeated head impacts – at death, finds a study published by The BMJ today.
Players whose brains showed the most advanced CTE (stage IV) were also more likely to have symptoms typical of dementia before death, such as memory loss and impaired cognitive function, the study found.
Previous studies have shown that people who experience repetitive head impacts from contact sports, including NFL players, are more likely to develop and die from neurodegenerative disease such as CTE than the general population.
However, CTE can only be confirmed by post-mortem examination, so the extent of CTE among NFL players and its association with symptoms such as dementia has been unclear.
To address this, the researchers studied brain tissue donated to the UNITE brain banks at the Boston University CTE Center (333 donors) and Mount Sinai (1 donor), and UCSF ADRC brain bank (4 donors) by American football players who died between 2008 and 2021 and had played at least one NFL game after 1949 (the first year plastic helmets were mandatory) to estimate rates of CTE among this group.
They also accessed players’ medical notes for symptoms typical of dementia during life and reviewed medical histories from clinical interviews with family members or other informants to examine the association between advanced stage CTE and dementia.
Study clinicians confirmed dementia cases and cause of death using all available information. Average age at death was 66.5 years.
Among 1,712 NFL players who died from 2008 to 2021, 338 (19.7%) players’ brains were studied, 315 (93.2%) of whom had a diagnosis of CTE; thus, the possible CTE prevalence at death ranged between 18.5% and 98.7%.
Among those who died from 2016 to 2021, when brain donation was most frequent, the possible CTE prevalence at death ranged between 24.5% and 97.7%.
Among donors, 104 (30.8%) had stage IV CTE, 202 (59.8%) had dementia diagnosed by a study clinician, and 63 (18.6%) had neurodegenerative disease listed as the main cause of death.
Stage IV CTE in donors was associated with symptoms typical of dementia before death, and with a 44% higher prevalence of study clinician diagnosed dementia.
Because this retrospective observational study relied on post-mortem brain donation, causal interpretation requires caution. The researchers acknowledge several limitations, including that not all former NFL players who died during the study window were included and that some informants may have overemphasised or inaccurately recalled symptoms.
However, they say: “Together, these findings indicate that NFL players have a higher prevalence of CTE at death than has been previously shown in multiple community based studies. Furthermore, these data indicate that CTE severity at death is significantly associated with dementia in NFL player brain donors, and that dementia is common in these donors.”
Additional work is needed to further clarify the nature of this relation, particularly in other populations, with high lifetime exposure to repetitive head impacts, they conclude.
This study provides one of the most informative estimates to date of CTE burden among former NFL players, say researchers in a linked editorial.
The next challenge is to measure the long term neurological consequences of repetitive head impacts well enough to inform athletes, clinicians, sporting organisations, and policymakers, they write, alongside steps such as identifying CTE during life and continued efforts to reduce avoidable exposure while uncertainty remains.
Above all, existing and emerging evidence on this issue must be regularly shared with past, present, and prospective NFL players, ensuring that consent to play is obtained with knowledge of the potential risks involved and the limitations of the current research evidence, they conclude.
The BMJ
Observational study
People
Chronic traumatic encephalopathy prevalence at death in National Football League (NFL) players: retrospective case-cohort study of all NFL decedents from 2008 to 2021
25-Aug-2026
All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from the National Institute of Neurological Disorders and Stroke (NINDS), National Institute on Ageing (NIA), and the Maloney/ Carpenter Trauma-Related Neurodegenerative Disease Research Fund; DHD reported receiving personal fees for providing expert testimony related to traumatic brain injury and spinal cord injury, serving as a scientific advisor and options holder for StataDx and Solius Labs, serving as a scientific advisor for Eli Lilly, receiving research funding from the Football Players Health Study (FPHS) at Harvard University funded by the NFL Players Association (NFLPA), serving as a volunteer member of the Mackey-White Committee of the NFLPA, and receiving clinical funding from the Brain and Body Programme funded by the NFLPA, all outside the submitted work. CJN reported serving as a volunteer member of the Mackey-White Committee of the NFLPA, for which he receives travel support, and an advisor and options-holder with Oxeia Biopharmaceuticals and StataDx; receiving travel support from the NFL, NFLPA, World Rugby, World Wrestling Entertainment (WWE), and All Elite Wrestling (AEW); serving as an expert witness in cases related to concussion and chronic traumatic encephalopathy, and receiving compensation for speaking appearances and serving on the Players Advocacy Committee for the NFL Concussion Settlement; and being employed by the Concussion and CTE Foundation, a 501(c) (3) non-profit, which receives charitable donations. CBL reports receiving clinical funding from the Brain and Body Programme funded by the NFLPA outside the submitted work. JW reported receiving personal fees from the Alzheimer’s Association outside the submitted work. MJM reports receiving clinical funding from the Brain and Body Programme funded by the NFLPA outside the submitted work. GDR reported receiving research support from NIA, NINDS, Alzheimer’s Association, American College of Radiology, Rainwater Charitable Foundation, Alliance for Therapeutics in Neurodegeneration, Avid, GE Healthcare (all for New IDEAS); Genentech; serving as a paid consultant (SAB, past 36 months) for Alector, Eli Lilly, Merck, Novo Norodisk, Roche; serving as a paid DSMB member for Johnson & Johnson; and serving as associate editor of JAMA Neurology and JAMA. WWS reported grants from the National Institutes of Health, Chan-Zuckerberg Initiative, Bluefield Project to Cure Frontotemporal Dementia, and Rainwater Charitable Foundation during the conduct of the study, and personal fees from Biogen and Atheneum (consulting), and from Lyterian Therapeutics outside the submitted work; in addition, WWS had a patent for US Provisional Patent Application 63/085749 pending. LG reported receiving funding from the WWE and Ivivi Health Sciences. RDZ reported royalties from Springer/ Demos Publishing for serving as co-editor of the textbook Brain Injury Medicine; serving on the scientific advisory board of Myomo, onecare. ai, Kisbee, and NanoDiagnostics; being partially supported by the National Institute on Disability, Independent Living, and Rehabilitation Research; and funding from the FPHS, which is funded by the NFLPA. YT reported receiving personal fees from the American Medical Association outside the submitted work. RCC reported royalties from Houghton Mifflin Harcourt; compensation for expert legal opinion to the National Collegiate Athletic Association and National Hockey League; serving as a consultant for the Concussion Legacy Foundation; serving as a senior advisor and paid consultant to the NFL Head Neck and Spine Committee; serving as a member of the Mackey-White Committee of the NFLPA; serving as vice president of National Operating Committee on Standards for Athletic Equipment and chair scientific advisory committee and cofounder of Medical Director Concussion Legacy Foundation; and serving on the Medical Science Committee for the National Collegiate Athletic Association Student-Athlete Concussion Injury Litigation. RAS reported receiving personal fees from Eisai outside the submitted work and royalties for published neuropsychological tests from Psychological Assessment Resources; owning stock options as a member of board of directors for King-Devick Technologies; receiving grants from the National Institutes of Health (NIH), Life Molecular Imaging, and Rainwater Charitable Foundation during the conduct of the study; and receiving an honorarium from the Michael J Fox Foundation unrelated to this work, and royalties from Oxford University Press outside the submitted work. MLA reported receiving grants from Life Molecular Imaging and Rainwater Charitable Foundation and personal fees from Oxford University Press and the Michael J Fox Foundation outside the submitted work. ACM reported serving as a member of the MackeyWhite Committee of the NFLPA. JM reported receiving grants from the NIH outside the submitted work.