Researchers from Mass General Brigham, Boston University and the Concussion & CTE Foundation report that at least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy at the time of death - a rate far above what is seen in the general population. The findings, published in The BMJ, also show that 61.3% of NFL donors with CTE met clinical criteria for dementia, and that more severe CTE was more often accompanied by dementia.
The estimate comes from an unusual piece of arithmetic. Because CTE can still only be confirmed after death by examining brain tissue, the team identified every former NFL player from the hard-shell helmet era who died between 2008 and 2021, then focused on the 2016 to 2021 window, when brain donations peaked. Of the 878 former players who died in that period, 235 donated their brains, and 215 of those brains - 91.4% - showed CTE. Treating those 215 as the only cases among all 878 deaths yields a floor of 24.5%.
That floor is deliberately conservative. At the other extreme, if every player who did not donate a brain also had the disease, prevalence would reach 97.7%. The researchers describe both ends as highly unlikely and say the real figure sits somewhere between them. Most of the analyzed brains came to the UNITE Brain Bank at the Boston University CTE Center, with additional cases from brain banks at Mount Sinai and the University of California San Francisco Alzheimer's Disease Research Center.
For families of former players, the dementia link is the part that lands hardest: CTE in this group was not a quiet pathology found only under a microscope but was frequently paired with clinical dementia, and more so as the disease advanced. Brain-bank samples are self-selected, which is precisely why the authors framed their result as a range rather than a single number - and why a reliable way to detect CTE in living people remains the field's central missing tool.