Study estimates about 75% of deceased former NFL players had CTE

A study published in JAMA Network Open estimates that about 75% of former NFL players who died from 2008 through 2023 had chronic traumatic encephalopathy, or CTE. Researchers adjusted their estimate to account for brain donation bias, since families of players with cognitive symptoms were about five times more likely to donate brains than families of players without symptoms. About 93% of donated brains showed signs of CTE, according to NBC News.

The study also estimated that 27% of the former players had dementia, which the study’s lead author said could have any cause. CTE can be definitively diagnosed only after death, CBS News reported. The researchers said the estimate applies to deceased players and does not predict how many living or active players have CTE.