The number that should terrify the NFL isn't a defensive stat. It's 24.5 — the minimum percentage of former NFL players who died between 2016 and 2021 found to have chronic traumatic encephalopathy (CTE) in a landmark study published Tuesday in The BMJ. And the researchers' worst-case estimate is almost too grim to say out loud: as high as 97.7 percent.
The study, led by Dr. Daniel Daneshvar of Mass General Brigham and Harvard Medical School with Boston University's CTE Center and the Concussion & CTE Foundation, analyzed 1,712 former NFL players who died between 2008 and 2021. Of the 338 brains donated for examination, a staggering 93.2 percent showed CTE pathology. The researchers then extrapolated that to the full cohort — every player who appeared in at least one NFL game since 1949 — and arrived at a minimum prevalence of 24.5 percent. One in four. Minimum.
The 93 Percent That Everyone Keeps Misreading
Here's where the conversation usually goes off the rails. The "93 percent of donated brains" figure is real, but it's also misleading — brain banks have always skewed toward players whose families suspected something was wrong. That's precisely why this study matters: it's the first serious attempt to answer the question nobody wanted to ask. Not "how many players who donated their brains had CTE?" but "how many players who died had CTE?" The answer, at the floor: roughly one in four. The ceiling, if you assume virtually every player carried the disease except the 20 brains definitively cleared: nearly everyone.
"The true rate of CTE at death in NFL players is somewhere in the middle," Daneshvar told NPR. Middle, in this case, is a terrifying place to be — because even the low-end estimate is far higher than the general population rate, where CTE affects less than 1 percent of people.
The Hard-Shell Era Came With a Hidden Price
Every player in this study came from the hard-shell helmet era — the generation that built the modern NFL into a $20 billion-a-year monster. They played through concussions, got up slow, and went back in. The league changed the rules, softened the game, and wrapped players in Guardian Caps. But the damage was already done, and the dose-response relationship is brutal: the more you play, the higher your risk. BU CTE Center co-director Dr. Jesse Mez warns that the same math could apply to college and even high school players — a slow-motion public health reckoning that extends far beyond the NFL.
The study also found that more than 90 percent of players with Stage IV CTE — the most advanced form — had been diagnosed with dementia in life. That's the closest thing yet to a roadmap for identifying living players most likely to be suffering, and it lands like a grenade in the middle of the NFL's concussion settlement math.
The Settlement That Now Looks Like a Bargain — for the League
Here's the uncomfortable angle nobody in the league office wants to discuss: the NFL's landmark concussion settlement was built on actuarial assumptions from an era when CTE prevalence was treated as unknowable. This study just made it knowable — and the true burden is almost certainly multiples of what the settlement's baseline assumed. The NFLPA called the findings "a sobering reminder that football carries real risks" and "a call to action across the entire football ecosystem." The NFL's response was boilerplate: the league "continuously strives to make the game of football safer."
But here's the tension that should make every fan pause: the league that markets violence on Sunday is now paying quietly for the consequences on every other day of the week. The settlement was supposed to be the final word. Studies like this one suggest the final word hasn't been written yet — and the next CBA negotiation, whenever it comes, will be fought in the shadow of a 97.7 percent worst-case scenario.
What This Means for Football's Future
The existential threat to the NFL has never been the XFL, or flag football, or declining ratings. It's this: a parent reading this study and deciding their kid doesn't play tackle football. Youth participation has been sliding for years, and studies like this one are the accelerant. The league can put a Guardian Cap on every helmet in America — and it's trying — but you can't cap the compounding interest of a generation of head trauma that's already been paid out in full.
The prediction here is simple and probably unpopular: within a decade, the NFL will quietly expand its settlement payouts, fund a wave of CTE-diagnosis research with suspicious urgency, and market safety harder than it has ever marketed anything — not because the league grew a conscience, but because the math finally caught up. One in four dead players, minimum, is a number that doesn't settle. It compounds.
The next time you watch a defensive back lower his helmet into a tackle, remember the study's real finding isn't the 93 percent of donated brains. It's the 24.5 percent floor — and the uncomfortable reality that the true number, like the league itself, is probably somewhere in the middle. And the middle is where the NFL's biggest bet of all is still being graded.
Lauren Mitchell
Lauren Mitchell covers sports with a focus on roster movement, coaching trends, player development, and the bigger storylines behind each matchup.