At Least One in Four Former NFL Players Who Died Had CTE
At least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, according to research published Tuesday. The study’s authors are clear that 25 percent is a floor rather than an estimate, and that the true figure is almost certainly higher.
The work came from Boston University, Mass General Brigham and the Concussion and CTE Foundation.
What the Researchers Actually Counted
The team examined the deaths of 1,712 former NFL players, drawing on postmortem data, medical records and clinical histories. Of that group, 338 had donated their brains for evaluation or research.
The headline finding sits inside a narrower slice. Among 878 former players who died between 2016 and 2021, 235 had donated their brains. Of those 235, 215 were diagnosed with CTE.
That is a diagnosis rate above 90 percent within the donated group, which is where the two very different numbers in this study come from.
Why the Range Runs From 25 Percent to Above 95
This is the part worth understanding before the headline number gets quoted anywhere. Brain donation is not random. Families typically donate when they suspect something was wrong, which means the donated group is weighted toward players who showed symptoms.
To produce the 25 percent floor, the researchers effectively assumed that none of the players who did not donate had CTE. That assumption is certainly false, and it is chosen deliberately to produce a figure that cannot be argued down.
The upper bound in the study runs above 95 percent, built on the opposite assumption. Neither end is the answer. What the range establishes is that the real figure is above one in four, and the study is built so that the floor holds regardless.
How That Compares to Everyone Else
CTE has previously been shown to affect well under 1 percent of the general population. Against that baseline, even the conservative floor in this study is a different order of magnitude.
The disease can only be diagnosed after death by examining brain tissue, which is the constraint shaping all research in this area. There is no test for a living player, and that is why donation studies remain the only route to a population estimate.
What CTE Does
CTE is a progressive neurodegenerative disease associated with repeated head impacts. Reported symptoms include memory loss, confusion, impaired judgment, impulse control problems, aggression, depression and eventually progressive dementia.
The link is to repeated impacts rather than to diagnosed concussions specifically, which matters for how the risk is understood. A player who never had a recorded concussion still absorbed thousands of sub-concussive hits across a career.
What It Means for Football Now
The players in this study came through an era before the current concussion protocols, the practice-contact limits and the rule changes on head contact. Whether those measures change outcomes is a question that cannot be answered for decades, because the answer arrives postmortem.
New Jersey has one of the larger youth and high school football participation bases in the Northeast, and both the Jets and the Giants train in the state. Research like this lands differently in a place where the sport is a weekly civic fixture.
What the Study Does Not Say
It does not establish that a quarter of all former NFL players have CTE. It addresses those who died in a specific six year window, and the donated brains inside that group.
It also does not identify who is at risk while alive, because that diagnosis is not currently possible. What it does is replace an argument about whether the problem is widespread with a floor that is hard to dispute.
Why the Floor Matters More Than the Ceiling
Previous CTE research has been dismissed on exactly the sampling problem this study builds around. If a lab reports that 90 percent of the brains it received had CTE, the obvious response is that families donate when something was wrong.
Designing the analysis to produce a number that survives that objection is the methodological point of the paper. The 25 percent figure is deliberately pessimistic about its own case, which is what makes it difficult to argue with.
What Would Move the Science Forward
A diagnostic test for living patients is the thing everyone in the field is working toward. Imaging and fluid biomarkers are both being investigated, and none is established well enough for clinical use.
Until one exists, prevalence work depends on donated tissue and every study carries the same caveat. That is a limitation of the field rather than of this particular paper.
For families, the practical consequence is that a definitive answer about a relative arrives only after death, and only if the brain is donated. That is a difficult thing to ask of people who are grieving, and it is the reason these sample sizes stay small.
