Study Estimates About 75% of Deceased Former NFL Players Had CTE
A new study estimates that about 75% of former NFL players who died over a 15-year span had evidence of chronic traumatic encephalopathy, or CTE. The disease is a degenerative brain condition linked to repeated blows to the head. The study was published Wednesday in JAMA Network Open, a peer-reviewed medical journal, and was conducted by a team based in Boston.
CTE can only be confirmed after death, when doctors examine brain tissue under a microscope. That is why research like this depends on families who agree to donate a relative's brain for study.
The study examined estimated CTE prevalence among NFL players who died from 2008 through 2023. Its analysis included records from 2,362 deceased former players, who spent an average of five years in the league.
Of the nearly 400 players whose brains were donated for examination, 93.5% showed evidence of CTE. That figure applies only to the donated group, while the roughly 75% estimate covers the broader set of deceased players. The two numbers describe different groups, so they should not be read as one statistic.
Researchers also estimated that about 27% of the former players in the analysis had dementia. Yorghos Tripodis is the study's senior author.
The authors put those NFL results next to other brain collections. They reported that less than 1% of brain samples from community-based brain banks contain evidence of CTE. Brain banks are collections of donated tissue, and the difference between the two groups is one of the points the study highlights.
The research builds on earlier Boston work. A 2023 study from Boston University found CTE in 345 of 376 former NFL players whose brains were examined. The new paper extends the timeline and adds the estimate for all deceased players in the 2008 to 2023 window.
For fans, the findings add weight to a question the league has faced for years: what repeated contact does to players over a lifetime. Some of the players in this study spent only a few seasons in the NFL, since the average career length in the analysis was five years. Those who follow the game closely will likely watch how the league and players' groups respond to research like this in the seasons ahead.
The full paper is available through JAMA Network Open under DOI 10.1001/jamanetworkopen.2026.40884.
