Study finds at least 24.5% of former NFL players who died 2016–2021 had CTE

A study published Tuesday in The BMJ found that at least 24.5% of former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, or CTE, at death — a deliberately cautious estimate that tries to move beyond years of attention-grabbing findings from self-selected brain donors.

The researchers identified 878 former NFL players who died during that six-year period. Of those, 235 donated brains that were examined after death, and 215 of those 235 donors — 91.4% — were diagnosed with CTE. Rather than treating that donor-only figure as the rate among all former players, the study used all 878 deaths as the denominator. That produces a minimum estimate of 215 out of 878, or 24.5%, because it assumes that none of the players who did not donate their brains had CTE.

That assumption is almost certainly too strict, which is why the authors reported a range rather than a single prevalence figure. Brain donation is not random, and players with troubling symptoms may be more likely to come to medical attention and eventually donate. At the same time, CTE can currently be definitively diagnosed only after death through examination of brain tissue, making it impossible to know the true population prevalence from living players. For 2016 to 2021, the paper said the prevalence at death could plausibly range from 24.5% to 97.7%, with the upper bound reflecting the opposite extreme assumption that every non-donor also had CTE.

The paper, published Aug. 25, 2026, used what the authors described as a retrospective population-based cohort and case-cohort design. Lead and corresponding author Daniel H. Daneshvar, a physician-scientist affiliated with Mass General Brigham, and senior author Dr. Jesse Mez, along with colleagues from Boston University’s CTE Center and other academic institutions, linked known former NFL deaths to available neuropathology data. Most of the examined brains came from the UNITE Brain Bank at Boston University’s CTE Center, with additional tissue from Mount Sinai and the University of California, San Francisco Alzheimer’s Disease Research Center. Diagnoses were made using established neuropathology criteria.

That approach is what sets the study apart from earlier high-profile CTE research. A widely cited 2017 paper found CTE in 110 of 111 former NFL players whose donated brains were examined. But the authors of that study and others cautioned that donor samples are convenience samples, not population snapshots, and likely overrepresent people with symptoms. The new paper asks a different question: not how many brain donors had CTE, but what the minimum prevalence must have been among all known former NFL players who died in a defined period.

Across the full 2008-2021 study window, the researchers identified 1,712 former NFL player deaths, with 338 brains studied and 315 cases of CTE. That translated to a possible prevalence-at-death range of 18.5% to 98.7%. Among the brain-donor sample, the burden of illness was also substantial: 61.3% of NFL donors with CTE met clinical criteria for dementia, and 95.5% of donors categorized as having dementia had CTE pathology.

“To find that somewhere between 24.5% and 97.7% of NFL players from that time period had this progressive brain disease is a wake-up call for the NFL and scientific communities,” Daneshvar said in a Mass General Brigham press summary cited by MedicalXpress.