A recent study conducted by researchers at Boston University indicates that approximately 75% of deceased National Football League (NFL) players examined had some degree of chronic traumatic encephalopathy (CTE). The study, which analyzed the brains of over 2,300 former players who died between 2008 and 2023, found that out of 396 individuals who donated their brains for research, 93.5% showed signs of CTE.
CTE is a progressive, degenerative brain disease associated with repeated head impacts, rather than a single injury. The disease can only be definitively diagnosed after death. Researchers estimated that former NFL players who experienced cognitive symptoms during their lives were roughly five times more likely to donate their brains for study than those without such symptoms. These donors also died at a younger average age, around 67, compared to the overall study group average of nearly 75.
The study also found that an estimated 27.2% of the players had a history of all-cause dementia during their lives, though it did not establish a direct causal link between CTE and dementia in these cases. The researchers noted that many diagnosed cases may have been in early stages and potentially symptom-free at the time of death.
This finding adds to previous research on the prevalence of CTE in former professional football players. A study released in August estimated that up to one in four NFL players might develop CTE during their lifetime. Symptoms associated with CTE can include memory loss, mood swings, and erratic behavior.
The connection between football and CTE gained significant public attention following the deaths of prominent players like Junior Seau and Mike Webster, both of whom were diagnosed with the disease posthumously. Dr. Bennet Omalu's examination of Mike Webster's brain led to the first diagnosis of CTE in an NFL player, which spurred a broader awareness of concussions and their potential long-term effects in the sport.
While CTE is most commonly associated with football players due to the frequent head impacts, it has also been identified in athletes from other contact sports such as hockey and rugby. The NFL has reported an increase in documented in-game concussions, with 168 recorded in the 2025 season, a 30% rise from the 129 recorded in the 2024 season. These figures do not include the total number of evaluations or medical timeouts during games.