08/27/2026
A new study of former National Football League (NFL) players who died between 2016 and 2021 has found that at least a quarter had chronic traumatic encephalopathy (CTE). A worst-case scenario estimate from the study suggests that the number of impacted players could potentially be above 95 percent. By comparison, the rate of the neurodegenerative disease in the general population has previously been shown to be far lower, with CTE affecting perhaps less than 1 percent of people.
The findings, by researchers at BU CTE Center, Mass General Brigham, and the Concussion & CTE Foundation, have been described as a “wake-up call” for scientists and the football community.
Researchers analyzed the deaths of 1,712 former NFL players, including 338 who had donated their brains for evaluation or research. They examined postmortem data, medical records, and clinical histories, as well as the neuropathology, or disease profile, of the donated brains.
The team found CTE in 93.2 percent of the donated brains, a figure researchers extrapolated out to suggest that among all those who died, the prevalence of the disease would, at a minimum, be 24.5 percent—but could be as high as 97.7 percent. All of the players in the study were from the NFL’s hard shell helmet era. The findings were published in the BMJ.
That minimum prevalence of CTE “is higher than expected,” says Jesse Mez, a BU CTE Center codirector of clinical research. “If at least 25 percent of NFL players who died had these changes in their brain, then this seems like a call to action for more discussion about risk, more research, and more support for affected families.”
The Boston University CTE Center has published more than 100 studies and been instrumental in linking the progressive neurodegenerative disease to a range of symptoms, including memory loss, problem solving difficulty, aggression, poor impulse control, and slow movement. It has also found CTE in a high proportion of contact sport athletes studied, particularly former pro football players. The center, which hosts the largest brain bank of its kind in the world, has pinpointed repeated hits to the head as a cause of CTE and other negative brain changes.
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