Nearly 75% of National Football League players who died between 2008 and 2023 had chronic traumatic encephalopathy, or CTE, according to a new study led by Boston University researchers and published in JAMA Network Open.
CTE is a degenerative brain disease that affects individuals who have experienced repeated blows to the head. Because it can only be definitively diagnosed after death, researchers must rely on brain tissue donations. While the condition is rarely seen in the general population, it appears at significantly higher rates among deceased professional football players.
Lead author Julia Gallini noted the contrast between general brain banks and the cohort of former athletes. With CTE consistently found in less than 1% of donors to community brain banks, an estimated 75% prevalence among former NFL players over a 16-year period is concerning. Gallini emphasized that these findings highlight the need to increase efforts to support families, diagnose CTE during life, and treat related symptoms.
The new findings build upon previous research released by Boston University in August, which estimated that anywhere from 25% to 98% of former NFL players who died between 2016 and 2021 had the disease. That wide range reflected uncertainty regarding how representative brain donors were of the overall former player population, as donors were more likely to have experienced symptoms associated with CTE, introducing selection bias.
To address this statistical challenge in the latest research, investigators factored in that former NFL players with cognitive symptoms were five times more likely to have their brains donated to science. Researchers used this estimated selection ratio to adjust the raw 94% prevalence observed among the 387 deceased ex-players studied—of whom 362 were found to have some form of CTE—down to an overall population estimate of 74.5%.
Study authors noted that the research evaluated only former NFL players who have passed away and does not predict how many living former or active players might have the condition. Former NFL quarterback Matt Hasselbeck, who serves as an ambassador for the study, spoke about the impact of the data on those who built the sport.
Both the league and the players’ association responded to the publication. The NFL stated that it continuously strives to make football safer by implementing strategies to reduce concussions and head impacts, pointing to the introduction of better equipment such as Guardian Caps and specific rule changes. The league emphasized its commitment to providing the NFL community with expanded resources to enhance physical and mental well-being and encouraged former players to seek treatment when concerned about their health.
The NFL Players Association called the study one of many that are critical to understanding the long-term health impacts of football. The union affirmed its commitment to supporting scientific research, investing in resources that aid player well-being, and expanding access to care.
Individual figures from the football community also reflected on the inherent risks of the sport. New England Patriots head coach Mike Vrabel, a former linebacker, stated that players understood what they were signing up for when they decided to play. He added that while he believes the league is trying to make the game safer and better, the NFL should do everything it can to protect players’ quality of life.
