A Boston University study estimates that 74.5 percent of former NFL players who died from January 2008 through December 2023 had CTE. This brain disease is linked to repeated head injuries. It can only be diagnosed by examining the brain after death.
The research included more than 2,300 former players. Almost 400 had brains donated to the university’s brain bank, while the remaining players were identified through US death records. The team estimated that families were five times more likely to donate a brain if the player had experienced symptoms associated with CTE.
Because of this difference, donated brains may not represent all former players fairly. A 2017 study based on brain donations estimated a CTE rate of 99 percent. By accounting for the difference in donation rates, the new team produced the first population-level estimate for NFL players, rather than an estimate based only on donated brains.
People later diagnosed with CTE may experience memory problems, difficulty concentrating, depression, and trouble controlling their behavior. Researchers also estimate that about one in four players in the group had dementia, which affects memory and thinking. Dementia is a common feature of late-stage CTE.
