Study estimates CTE in nearly 75% of former NFL players who died from 2008 to 2023

A study published in JAMA Network Open estimates that 74.5% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, a degenerative brain disease associated with repeated head impacts.

Researchers from Mass General Brigham, Boston University and the Concussion & CTE Foundation examined records for 2,362 deceased former players. Of 387 players whose brains were donated for examination, 362, or about 94%, had some degree of CTE neuropathology.

Because families may be more likely to donate the brains of players who showed cognitive symptoms, the researchers adjusted for selection bias. They estimated that players with such symptoms were about five times more likely to have their brains donated, reducing the estimated prevalence across the full group to 74.5%. By comparison, CTE is found in less than 1% of donors to community brain banks, according to the researchers.

The authors cautioned that the estimate applies only to former NFL players who died during the study period. It does not indicate how many living former or active players have CTE, which can currently be definitively diagnosed only after death. The presence of CTE pathology also does not necessarily mean a person experienced dementia or cognitive decline.

The NFL said it continues to pursue rule changes, improved equipment and other measures intended to reduce concussions and head impacts. Outside experts told CBS News that the study used strong methods but that the estimate may still be too high and should not be applied to current athletes or participants in nonprofessional contact sports.