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At Least 25 Percent. Possibly Nearly All of Them.
A study published today in the British Medical Journal found that at least 24.5 percent of former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, CTE. In the general population, the rate is below one percent. That four-in-four-hundred versus one-in-four gap is the story. But the study also contains a worst-case number that is harder to sit with: if the pattern of brain donation holds across all players who did not donate, the true prevalence could be as high as 97.7 percent. Researchers from Harvard Medical School, Boston University, and Mass General Brigham are careful to say that figure is an upper bound, not a claim. What they will say directly is that this is now a public health problem, not a statistical curiosity.
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:STATS
[icon:CHART] Former NFL players analyzed | 1,712
[icon:CHART] Brains donated for study | 338
[icon:TARGET] Donated brains with CTE confirmed | 93.2%
[icon:BOLT] Minimum prevalence estimate (all who died) | 24.5%
[icon:FIRE] Maximum prevalence estimate (worst case) | 97.7%
[icon:USERS] CTE rate in the general population | less than 1%
[icon:CLOCK] Higher neurodegenerative death rate vs. general pop | 4 times
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:INFO
What CTE Does to a Brain
Chronic traumatic encephalopathy is caused by repeated blows to the head, not by any single concussion. Each impact triggers a cascade that deposits an abnormal form of the tau protein in the brain. Over years and decades the deposits spread, disrupting the regions that govern memory, emotion, and impulse control. Symptoms while alive include memory loss, depression, extreme mood swings, and in advanced cases dementia. The disease cannot be diagnosed in a living person. There is no scan, no blood test, no symptom list that confirms it. The only definitive diagnosis comes from examining brain tissue after death, which is why every CTE study begins with a donation and ends with a count of what was found. The brains in this study came from the UNITE Brain Bank at Boston University, the world's largest collection of its kind, now holding more than 330 brains donated by former NFL players since 2008.
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:QUOTE [quotetype:plain, subtitle:Dr. Jesse Mez]
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, research, and support for affected families.
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Why the True Number Could Be Much Higher
The 24.5 percent figure is a conservative floor. It comes from a simple calculation: 215 of the 338 donated brains showed CTE, and 338 is 19.7 percent of the 1,712 former players who died during the study period. The problem is that brain donation is not random. Players who experience severe symptoms, memory loss, rage, depression, suspected dementia, are far more likely to donate. Their families know something is wrong and want answers. Players who die without neurological symptoms are far less likely to end up in a brain bank at all. That selection effect means the 93.2 percent CTE rate among donated brains almost certainly overstates the true rate. But it means the 24.5 percent floor, built on the assumption that every non-donated brain was clean, almost certainly understates it. The researchers modelled a range from 24.5 to 97.7 percent and declined to pick a point inside it. Dr. Daniel Daneshvar of Harvard Medical School, a lead author on the study, noted that former NFL players a
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A Sport Now Confronting Its Own Evidence
The study covers players who wore hard-shell helmets, the gear that has defined the NFL since the 1970s. It does not resolve whether modern helmet designs or rule changes that ban certain hits have reduced the underlying risk. What it does is put a prevalence floor on the problem for the first time in a peer-reviewed study large enough to be taken seriously. The researchers call for prevention measures focused on cutting repetitive head impacts at every level of the sport, not just in the professional game. Youth and college players absorb the same forces. The NFL has paid out more than one billion dollars in concussion settlements since 2013. This study is the first to provide a population-wide estimate of how common the outcome of that exposure actually is. The authors say the next step is longitudinal data: following players while they are still alive, measuring neurological function over time, and correlating that with career length and position, so that athletes can give genuinely
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:LINK
https://www.bu.edu/articles/2026/many-former-nfl-players-had-cte-before-death
Boston University CTE Center: study findings and BMJ paper (primary source)