A study published October 28, 2026 in JAMA Network Open estimates that about 74.5% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) at the time of their death.

Researchers from Boston University's CTE Center examined 2,362 deceased former players, of whom 396 had donated their brains for research. Among the brain donors whose CTE status was determined, 93.5% showed CTE neuropathology.

Study investigator Yorghos Tripodis, a Boston University professor of biostatistics, told Medscape the key takeaway is that 'CTE neuropathology is common, not rare, among former NFL players.'

The finding is surprising because it narrows an enormously wide range. An August study in The BMJ could only estimate that somewhere between 24.5% and 97.7% of former players who died between 2016 and 2021 had CTE, reflecting uncertainty about how representative brain donors were.

Even under a conservative lower-bound analysis, the new study puts the estimate at 63.7%, and Tripodis told ABC News that even under very conservative assumptions the estimate does not fall below 60%. By comparison, CTE found in brain banks in the general population is estimated at less than 1%.

Because CTE can only be diagnosed after death, researchers worry that families who noticed cognitive symptoms are more likely to donate a loved one's brain, inflating apparent rates. The study found players with cognitive symptoms were about five times more likely to have their brains donated.

To adjust, researchers combined brain bank data with National Death Index records and dementia and mild cognitive impairment data from the 2022 NFL-Long study, applying a selection ratio to estimate prevalence across all deceased players.

The estimated prevalence of all-cause dementia history during life among the players was 27.2%.

Experts not involved in the study cautioned against overextending the results. Dr. Kristen Dams-O'Connor of Mount Sinai told CBS News the results 'cannot and should not be interpreted as being representative of current living athletes,' since many studied players ended careers long ago.

Dr. Jon LaPook noted the research measured signs of CTE in the brain, not actual symptoms. Dr. Rachel Grashow of Harvard told CNN that researchers found higher dementia rates only in stages III and IV CTE, and Tripodis said not everyone with CTE pathology will develop severe symptoms.

The NFL said it 'continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts,' and remains committed to expanding resources for players' physical and mental well-being.

The NFLPA called studies like this 'critical to improving our understanding of football's long-term impacts' and said it remains committed to supporting research and expanding access to care.

The league has implemented rule changes to reduce concussions and introduced protective equipment including Guardian Caps, which Dams-O'Connor said should translate to lower CTE risk in recent generations of players.

Researchers say the field still needs a reliable biomarker to diagnose CTE in living patients; Tripodis told Medscape that such a tool would let scientists follow people over time and learn why some with CTE pathology develop symptoms while others do not.

Dr. Jay Alberts of the Cleveland Clinic told CBS News that studying activities like driving or balancing a checkbook may reveal early changes, and Dr. Jeremy Tanner of UT San Antonio said long-term studies of players could benefit research into other neurodegenerative diseases.

Chris Nowinski told Medscape the 75% estimate should spur support for former players and prevention at youth levels, while the family of former player Wesley Bender, diagnosed posthumously with stage 2 CTE, is speaking out for youth protections.