A research team from Boston University has recalibrated previous data regarding “brain donation bias” and estimates that approximately 74.5% of former National Football League (NFL) players who passed away between 2008 and 2023 were suffering from chronic traumatic encephalopathy (CTE) at the time of their death. This marks the first population-level estimate of CTE prevalence among NFL players.
The findings from this study were published on October 28, 2026, in the *JAMA Network Open*, a notable journal dedicated to medical research.
CTE is a degenerative brain condition linked to repeated head trauma that can only be diagnosed post-mortem through an autopsy. Individuals afflicted with CTE may exhibit symptoms such as memory issues, difficulties with attention, depression, and poor impulse control while alive. While primarily associated with contact sports, CTE can also affect individuals who have experienced intimate partner violence or those who have served in military combat. Research has previously indicated that the longer a person participates in American football, the higher their risk of developing CTE, along with more severe manifestations of the disease.
A 2017 analysis of brain donations had estimated that a staggering 99% of former NFL players were found to be suffering from CTE. However, this figure may be skewed. Families tend to donate the brains of loved ones who exhibited CTE-related symptoms during their lifetime, thus resulting in a sample that is heavily weighted toward players with pronounced symptoms.
The current study encompasses all former NFL players who died between January 2008 and December 2023, totaling more than 2,300 individuals. Among these, nearly 400 brain samples are stored in Boston University’s UNITE brain bank, while the remaining players were identified via the National Death Index.
The research team uncovered that players who exhibited CTE-related symptoms in life were five times more likely to have their families donate their brains compared to those without symptoms. By leveraging this discrepancy, the team executed statistical corrections that ultimately estimated a CTE prevalence rate of 74.5%, representing roughly three-quarters of the examined population.
Despite this corrected figure being significantly lower than the previously cited 99% from 2017, the estimated proportion of 74.5% still underscores the alarming long-term risks to brain health associated with a professional football career. It is essential to recognize that this study estimates the prevalence among deceased players and cannot directly translate to the lifelong risk for active players. Moreover, the report did not provide any official response from the NFL regarding the findings.
This research forms part of the ongoing discourse surrounding player health and safety in contact sports, illuminating the profound impact that such a demanding profession can have on the brain over time. As further investigations are conducted, they may provide deeper insights into preventive measures and the management of brain health among athletes, potentially altering the landscape of sports-related health awareness and protocols.