Study estimates that 75% of former NFL players who died between 2008-2023 had CTE

A new study estimates that nearly 75% of all NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) neuropathology. CTE is a neurodegenerative disease that has been diagnosed in individuals with substantial exposure to repetitive head impacts. It can only be definitively diagnosed after death.

This study, a collaboration among researchers at Mass General Brigham, Boston University and the Concussion & CTE Foundation, was published in JAMA Network Open. Researchers caution that the new study’s estimate of prevalence only applies to former NFL players after death. It does not predict how many living former players have CTE or how many active players are impacted.

The new findings build on an August 2026 study from the same research group that estimated that between 25% and 98% of former NFL players who died between 2016 and 2021 had CTE. The wide range reflected uncertainty about how representative brain donors were of the overall NFL population. Brain donors are more likely to have symptoms believed to be related to CTE, a concept known as selection bias.

“These findings are concerning, but they do not mean former NFL players are destined to develop dementia,” said co-author Daniel Daneshvar, MD, PhD, Chair of Physical Medicine and Rehabilitation at Mass General Brigham and Earl P. and Ida S. Charlton Associate Professor at Harvard Medical School. “In our clinic with former players, particularly those in midlife, we have had success improving cognitive symptoms, mental health and quality of life through both targeted treatments and proactive brain health strategies. While we cannot yet treat the underlying CTE pathology, our goal is to bend the curve of brain aging, extend brain healthspan and help players feel and function better throughout their lives.”

For the new study, researchers analyzed selection bias to estimate the prevalence of CTE in players they didn’t directly study. This estimate was made possible by understanding the differences between NFL players whose brains were donated and NFL players whose brains were not donated. Among the 387 deceased NFL players that were studied, 362 (94%) had some degree of CTE neuropathology. Researchers then studied available records of death certificates from the National Death Index for all 2,362 NFL players from this era, which included data on how many died of neurodegenerative disease and had dementia.

Researchers also analyzed other factors associated with brain donation, including cognitive symptoms, age at death, position and years played in the NFL. From this analysis, they estimated that former players with cognitive symptoms were about five times more likely to have their brains donated by their family than those without such symptoms. They used this estimated selection ratio to adjust the 94% prevalence of CTE observed among brain donors to an overall estimate of 74.5%.

This is the first estimate of CTE neuropathology prevalence among all 2,362 deceased former NFL players, including those who did not have their brains donated and were not measured directly. In comparison, CTE is rare in the general population and has been seen in less than 1% of thousands of brain donors to community brain banks in the United States, Australia, Austria and Brazil.

Not every player with CTE pathology will go on to develop symptoms, particularly in cases of early-stage disease. Among players who do develop symptoms of CTE, common manifestations include cognitive impairment, behavioral changes and dementia. Dementia is a general term for a severe decline in memory, reasoning and language function that interferes with everyday functioning and independence. Previous studies have shown NFL players develop dementia at four times the rate of the population. No other environmental or occupational exposure ever studied is known to have increased dementia risk at death by that much.

“We would like to thank the former NFL player community for their support of this research that is answering an important public health question on the relationship of tackle football and CTE,” said Yorghos Tripodis, PhD, senior author of this study and professor of biostatistics at Boston University School of Public Health. “We recognize these findings may cause concern for the community of living players and their families. We want them to know that we and others are standing by to provide support, and that we have hope for those living with CTE. Discoveries from the brain bank have already brought us significantly closer to a diagnosis during life, at which point our most important goal will be to develop effective treatments for CTE.”

Former NFL players concerned about their brain health should consider being evaluated by a clinician who specializes in neurodegenerative conditions. While it's not always possible to eliminate long-term risk, identifying and addressing modifiable risk factors can support brain health and improve quality of life.

If you're a former NFL player seeking guidance, support for mental health symptoms, help finding a specialist or support in managing your health, resources are available through The Trust Powered by the NFL Players Association (NFLPA), the NFLPA's Professional Athletes Foundation and the NFL Life Line, which provides 24/7 independent and confidential support (800-453-0078). All former athletes, veterans and anyone concerned about CTE can access support through the Concussion & CTE Foundation HelpLine.

Authorship: In addition to Daneshvar and Tripodis, authors include Julia Gallini, Michael L. Alosco, Bobak Abdolmohammadi, Jennifer Weuve, Ann C. McKee, Thor D. Stein, Robert A. Stern, Jesse Mez and Christopher Nowinski.

Disclosures: Daneshvar reports stock options with StataDx and Solius and personal fees from Medicolegal for expert testimony and Eli Lilly and Co. Additional author disclosures can be found in the paper.

Funding: This study was funded in part by the National Institutes of Health through the National Institute on Aging and National Institute of Neurological Disorders and Stroke (P30AG072978, U54NS115266, NCT02798185) and the Concussion & CTE Foundation.

Paper cited: Gallini J., et al. “Bias-Adjusted Prevalence of Chronic Traumatic Encephalopathy Among Deceased National Football League Players,” JAMA Network Open. DOI: 10.1001/jamanetworkopen.2026.40884

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