1 in 4 former NFL players who died from 2016 to 2021 had CTE, study estimates

By Nadia Kounang, CNN

(CNN) — At least 1 in 4 former National Football League players who died between 2016 and 2021 had chronic traumatic encephalopathy, according to a study released on Tuesday in the journal BMJ.

The study is “one of the most informative estimates to date of CTE burden among former NFL players,” an editorial that published along with the study said.

CTE is a neurodegenerative disease associated with repeated blows to the head. It can only be diagnosed after death, although symptoms can include memory loss, impulse control problems, anxiety, depression and anger issues. It’s most often seen in people who play sports such as football, hockey and soccer, but it has also been detected in the brains of soldiers who have been injured in explosions and in some people who experienced domestic violence. In the brain, it is marked by an abnormal buildup of the protein tau.

A separate recent analysis detected the disease in 99% of former NFL players who had donated their brains for research. However, a significant limitation of that study was that it was done in a population of people who were potentially biased because their brains had been donated by family members who may have noticed symptoms while their family members were living.

For this new study, researchers from Mass General Brigham, Boston University and the Concussion & CTE Foundation — many who had been involved in the previous CTE research — set to overcome that limitation by analyzing the total number of NFL deaths between 2008 and 2021. The researchers used death certificate data and compared it to the number of brain donors with confirmed CTE. The researchers further narrowed the time period down to 2016 and 2021, when the highest number of brain donations had been received.

Of the 878 former players who died in the time frame, 235 had donated their brains for research. Among them, 215 had been diagnosed with CTE. Many of the brain donations analyzed had been done at brain banks at Boston University and the University of California, San Francisco.

An NFL spokesperson said: “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 study’s lead author Dr. Daniel Daneshvar, the ​chair of physical medicine and rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School, said ​that repeated traumatic brain injuries are a known factor in elevated rates of neurodegenerative disease.

“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.

The ​study also found dementia was common among ​brain donors, with researchers urging prevention measures that focus on cutting down on 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.

The NFL’s 2011 Collective Bargaining ​Agreement limited the number ​of contact practices during the ⁠season. The current CBA was ratified in 2020 and runs through March 2031.

The Ivy League banned full-contact tackling during practices five years later.

The Supreme Court cleared the way for the NFL’s settlement of concussion-related lawsuits with thousands of retired ​players in 2016.

“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.

“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.”

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Jill Martin and Reuters contributed to this report.