A new study published in the British Medical Journal found that somewhere between 25% and 97.7% of former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, the degenerative brain disease caused by repeated blows to the head. Let that range sit with you for a second. The floor is one in four. The ceiling is essentially everyone. The NFL's response was to remind players that resources are available.
What the Study Actually Found
Researchers at Mass General Brigham, Boston University, and the Concussion & CTE Foundation started with 878 former NFL players who died during the six-year window between 2016 and 2021. Of those, 235 donated their brains to science. Of those 235 donated brains, 215 came back positive for CTE. That's a 91.4% hit rate among the brains researchers actually got to examine.
Because most players don't donate their brains, and because CTE can only be definitively diagnosed by dissecting brain tissue after death, researchers had to build a range. Their conservative minimum was 24.5%. Their maximum, which assumed every player had CTE except for the 20 whose brains had been definitively cleared, was 97.7%. As CBS News reported, the researchers themselves said "the true prevalence likely lies somewhere in the middle" — but the middle of 25% and 98% is still a catastrophe.
The study was published Tuesday in The BMJ, one of the most prominent medical journals in the world. The lead author, Dr. Daniel Daneshvar, is the chair of physical medicine and rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School. This is not a fringe paper from a fringe lab.
Four Times More Likely to Die From Brain Disease Than You
To understand how bad these numbers are, you need a baseline. According to CBS News, CTE affects less than 1% of the general population. Daneshvar told reporters that NFL players die from neurodegenerative disease at roughly four times the rate of the general public. The new study suggests that rate may be a dramatic undercount.
The research also found a brutal link between CTE severity and dementia. CBS News reports that 61.3% of former NFL players who donated their brains and had CTE met the clinical criteria for dementia. For those with the most advanced Stage IV CTE, NPR found that more than 90% were also clinically diagnosed with dementia based on medical records and accounts from loved ones. These are not men who felt a little foggy. These are men who lost their minds.
Dementia also showed up in 40% of samples that were entirely free of CTE, NPR noted, which means the sport appears to cause neurodegenerative damage through multiple pathways. The researchers called for urgent development of a cure. "These data, alongside my experience treating NFL players with dementia," Daneshvar told CBS News, "indicate that we need to dedicate resources towards developing a cure."
The Problem Started Long Before the NFL
One of the more damning findings in the study is where most of the damage actually happened. It wasn't in stadiums full of 80,000 people. According to BBC Sport, Daneshvar was direct: "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."
NBC News reported Daneshvar's statistic that nearly 70% of head impacts happen in practice, not games. His conclusion from that fact is actually the most actionable piece of the whole study: you don't have to change a single minute of game time at any level to substantially reduce the lifetime head impact burden on young athletes. You just have to stop running full-contact tackling drills six days a week at high school practice. The NFL itself figured this out with its 2011 Collective Bargaining Agreement, which limited in-season contact practices. The Ivy League banned full-contact tackling during practices in 2016. The suggestion is that everyone else follow suit.
The researchers were explicit on this point, NBC News found, urging that prevention efforts "focus on reducing repetitive head impacts that drive CTE risk, not just concussions." Concussions are the dramatic, visible injury. The slow grind of subconcussive hits, absorbed across years of practice reps, is what the science increasingly points to as the real killer.
The NFL's Response Was Exactly What You'd Expect
An NFL spokesperson issued a statement that multiple outlets including BBC Sport, CBS News, and NBC News all received what appears to be the exact same boilerplate paragraph. The league "continuously strives to make the game of football safer." Resources are available. Former players are encouraged to utilize them. No commitments. No acknowledgment of the specific findings. No mention of 97.7%.
This is, to be fair, a legally careful response from an organization that in 2016 agreed to a $1 billion settlement with more than 5,000 former players after a long-running class action over concussion-related injuries, as BBC Sport noted. The NFL admitted a link between football and brain disease back in 2016 as well. They've known. The question has always been what they plan to do about it.
What they have done, concretely, includes the practice limitations in the 2011 CBA and various rules changes aimed at reducing certain kinds of hits. Researchers are willing to acknowledge those steps. They're also saying clearly, in a peer-reviewed journal, that it isn't enough and that the changes need to reach youth and high school football before a single NFL paycheck changes hands.
The Brain Bank Numbers Tell Their Own Story
NPR reported that the UNITE Brain Bank at Boston University has received brains from more than 330 NFL players who died between 2008 and 2021. Of those, 93% have been diagnosed with CTE. Ninety-three percent. That number predates this study and has been sitting in the research literature, and yet the sport has continued more or less as designed.
The challenge has always been selection bias. Families who donate a loved one's brain to CTE research tend to be families who already suspected CTE, because they watched their husband or father or son change in recognizable ways before he died. Memory loss. Mood swings. Aggression. Depression. The players whose families never suspected anything, the ones who died in car accidents or from unrelated illness without obvious cognitive symptoms, generally didn't donate. That's why the 91% figure from donated brains isn't the whole story, and why this study's attempt to model the total population is so important.
Daneshvar and his team built their denominator by compiling a list of every player who appeared in at least one NFL game since 1949, then cross-referenced CDC death certificates to account for all players who died in the study window, not just the ones whose brains ended up in a lab. That's the methodological contribution that makes this paper significant. It's an honest attempt to count the uncounted.
The Dingo Take
The NFL has known about this for years. The league admitted a formal link between football and brain disease in 2016, paid out a billion dollars, and then the sport kept going, kept growing, kept signing billion-dollar broadcast deals. Sunday is still America's religion. None of that is secret. What this study does is put a number on it, or rather two numbers, and force the conversation about what falls between them.
And here's the part that should bother people beyond football: this isn't primarily an NFL problem. The damage accumulates in youth leagues and high school stadiums, in Friday night games in small towns where the coach has been running the same practice schedule for thirty years and nobody has told him the science changed. The NFL has resources and lawyers and liability exposure that gives them some incentive to update their protocols. A 16-year-old's high school program has none of those pressures. That's where the actual epidemic is being seeded, hit by hit, practice by practice, for decades before anyone gets drafted.
Daneshvar said we need to dedicate resources to finding a cure. He's right. But a cure for a brain disease that takes thirty years of accumulated trauma to develop is a long way off. The thing that could actually protect the next generation of players is already known. Fewer contact reps in practice. It wouldn't cost a dime, and it would be deeply unpopular in the states where football is closest to a civic religion. That's the real problem, and no study in any journal is going to solve it.
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