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CTE

At Least 25 Percent of Former NFL Players Had CTE When They Died, New Study Suggests

Boston University’s CTE Center helped lead research that found the neurodegenerative disease was common among players who died between 2016 and 2021; rate may even be as high as 97.7 percent

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 Boston University, 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, MD, MS, 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 BU 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.

“Because there is a rather linear dose-response relation between the amount of play and risk for CTE, we might also expect higher prevalence for college and high school players, too,” says Mez, a BU Chobanian & Avedisian School of Medicine associate professor of neurology and BU Alzheimer’s Disease Research Center associate director. “We have efforts underway to take a similar approach among former college football players. We are also using a geospatial approach to understand these relationships among football players at the county level.”

Because there is a rather linear dose-response relation between the amount of play and risk for CTE, we might also expect higher prevalence for college and high school players, too.

Jesse Mez, MD, MS

Mez’s coauthor, Daniel Daneshvar, MD, PhD, of Mass General Brigham and Harvard Medical School, says that finding that “somewhere between 24.5 percent and 97.7 percent of NFL players from that time period had this progressive brain disease is a wake-up call for the NFL and scientific communities.”

The researchers noted high rates of dementia among brain donors, a diagnosis that was also associated with severe CTE. In a previous study of 20,000 NFL players, Mez and his colleagues had found football stars were at a significantly increased risk of dying of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), dementia, and Parkinson’s disease.

There’s currently no way to diagnose CTE in life, though BU researchers are working on a number of projects that aim to change that, including Bank CTE, a major new study following people aged over 40 who played an organized or collision sport or served in the military.

And while there’s much work still to do to understand CTE, Mez says former football players—and others—experiencing symptoms can still get help.

“We recognize that these findings will be concerning for NFL players and their families, and we want them to know that help is available,” he says. “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.”

This BU Brink story was written by Andrew Thurston.