Study finds one in four former NFL players who died between 2016 and 2021 had CTE

A study released on Tuesday by 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). Of 878 former players who died in that period, 235 donated their brains for research and 215 of those donated brains were found to have CTE.

CTE can only be definitively diagnosed after death and is associated with repeated blows to the head, including concussions. The condition is linked to symptoms such as difficulty with attention and memory, dementia, mood disorders and headaches. The study’s lead author, Daniel Daneshvar, chair of physical medicine and rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School, said repeated traumatic brain injuries are a known factor in elevated rates of neurodegenerative disease.

Researchers reported that dementia was common among the brain donors and urged prevention measures that focus on cutting down repetitive head impacts across all levels of the sport. "The bulk of the head impacts that these former NFL players experienced didn’t occur at the NFL level. They occurred at the collegiate level ... and at the high school level and in many cases the youth level. And all of those cumulative hits to the head added up to result in an increased risk," said Daneshvar.

Daneshvar also pointed to broader mortality data in NFL players. "Similarly, we and others have shown that in NFL players, specifically, there is about a four times higher rate of death from neurodegenerative disease than the general population," he added, and urged changes in practice routines. "If the changes that have been implemented at the NFL level, including reducing the amount of contact in sports practices to less than one per week, were propagated at the collegiate, high school, and youth levels, athletes would be better off," said Daneshvar, who urged current and former athletes experiencing cognitive symptoms to seek a neurodegenerative disease expert evaluation.

An NFL spokesperson responded: "The NFL continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts. "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 well being. "We encourage former players to utilize these resources to identify and seek treatment when they are concerned about their health."

The report noted several policy and legal developments connected to concerns about head injuries in football: the NFL’s 2011 Collective Bargaining Agreement limited the number of contact practices during the season; the Ivy League banned full-contact tackling during practices five years later; and the US Supreme Court cleared the way for the NFL’s settlement of concussion-related lawsuits with thousands of retired players in 2016.

A number of high-profile NFL players who took their own lives — including Junior Seau, Dave Duerson and Aaron Hernandez — were found to have had CTE when their brains were analyzed after their deaths.

"We know that nearly 70% of head impacts are occurring in practice. So without changing a single minute of game time at any of those levels, we can be substantially reducing the cumulative head impact burden that these individuals are experiencing throughout their lives," Daneshvar said.