Between 2008 and 2023, approximately 75% of deceased former National Football League players were estimated to have suffered from chronic traumatic encephalopathy, according to findings published in JAMA Network Open.
Estimated Prevalence Among Deceased Players
The research marked a comprehensive attempt to establish a broader prevalence estimate for chronic traumatic encephalopathy among deceased former NFL players. To arrive at the 75% figure, investigators combined detailed brain tissue donations from 396 players with death record data from 1,966 players cataloged in the National Death Index. Among the subset of donated brains specifically, approximately 94% showed pathological evidence of the disease.
Researchers emphasized a critical distinction between the 94% observed in donated tissue and the 75% estimated across the wider deceased cohort. Previous scientific literature faced criticism for selection bias, as brain donations historically relied heavily on athletes who exhibited noticeable neurological symptoms during their lifetimes. In this new cohort, tissue donors tended to be younger at death, spent more years playing in the NFL, and included a higher percentage of white athletes compared to non-donors. Investigators adjusted their statistical models to account for these demographic and career differences.
Having chronic traumatic encephalopathy does not automatically equate to experiencing clinical symptoms during life, as the study authors noted. The research paper did not track or evaluate what specific symptoms individual players displayed before their deaths. Chronic traumatic encephalopathy is categorized into four distinct stages of severity, and the condition often remains in its early stages without manifesting overt cognitive or behavioral changes. The authors pointed out that a significant portion of the cases identified at autopsy were in early stages and might not have caused noticeable clinical impairment while the players were alive.
Limitations and Scope of the Data
The 75% estimation applies exclusively to deceased professional football players who competed in the NFL. Investigators stressed that the figures do not predict the prevalence of the disease among living former players, nor do they extend to college or youth tackle football participants. Examining lower levels of competition, such as high schools and universities, remains challenging due to a general scarcity of non-donor brain records and tissue samples. The study also differed significantly from an earlier paper published in August, which looked at a narrower window between 2016 and 2021 and estimated that one in four deceased players had the disease. Researchers cautioned that because the timeframes and analytical methods differed, the two figures cannot be used to track a temporal increase or decrease in prevalence.
Institutional Responses and Ongoing Research
Julia Gallini, the study’s lead author, described the estimated 75% prevalence as concerning and called for expanded efforts toward family support, antemortem diagnostic methods, and targeted treatments for symptoms associated with the condition. The NFL noted that it continues to implement strategies to reduce concussions and head impacts to improve safety, while encouraging retired athletes who have health concerns to utilize available medical evaluation and support resources. Meanwhile, the NFL Players Association reiterated that ongoing scientific research remains vital to fully understanding the long-term health impacts of professional football.
