BOSTON — A new study from researchers at Mass General Brigham, Boston University, and the Concussion & CTE Foundation found that at least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE), a degenerative brain disease linked to repeated head trauma.
The findings, published Tuesday in The British Medical Journal, examined former NFL players from the hard-shell helmet era and suggest the prevalence of CTE among professional football players is significantly higher than in the general population.
Researchers identified 878 former NFL players who died between 2016 and 2021. Of those, 235 donated their brains for study, and 215 of the donated brains, or 91.4%, showed evidence of CTE.
Because CTE can only be diagnosed after death through brain tissue examination, researchers estimated a range for how widespread the disease may have been among all deceased former players. Their most conservative estimate found at least 24.5% of former NFL players who died during that period had CTE. The upper estimate reached 97.7%, though researchers said both extremes are unlikely and the true prevalence is likely somewhere in between.
“Community brain bank studies have shown that CTE affects less than 1% of the general population,” said Dr. Daniel Daneshvar, lead author of the study and chair of Physical Medicine and Rehabilitation at Mass General Brigham. “To find that somewhere between 24.5% and 97.7% of NFL players from that time period had this progressive brain disease is a wake-up call for the NFL and scientific communities.”
Daneshvar added, “These data, alongside my experience treating NFL players with dementia in clinic, indicate that we need to dedicate resources towards developing a cure.”
The study also found a strong connection between CTE and cognitive decline. Researchers reported that 61.3% of former NFL players with CTE met clinical criteria for dementia. Among players diagnosed with dementia, 95.5% had evidence of CTE.
The most severe stage of the disease, Stage IV CTE, was strongly associated with dementia, as well as greater impairment in thinking, memory, and everyday functioning.
Researchers acknowledged that the findings may be troubling for former NFL players and their families but emphasized that treatment options are available for many symptoms associated with the disease.
“We have treatments for many symptoms believed to be associated with CTE, and in our clinic we find that symptoms can improve with proper medical care,” said Dr. Jesse Mez, a neurologist at Boston University and co-director of clinical research at the BU CTE Center.
In a statement in response to the findings, an NFL spokesperson told Boston 25 News, “The NFL continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts.”
The spokesperson added, “The NFL remains committed to ensuring that the NFL community has access to a robust - and expanding - set of resources to enhance their physical and mental wellbeing. We encourage former players to utilize these resources to identify and seek treatment when they are concerned about their health.”
The study’s authors said future research should focus on athletes who played more recently and on preventing the repetitive head impacts believed to drive CTE risk.
They also encouraged former NFL players concerned about their brain health to seek evaluation from medical specialists, noting that many conditions that resemble neurodegenerative diseases can be treated and that early intervention may improve quality of life.
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