Original studyJAMA Network Open, 2026Read the paper →
A new study estimates that about three in four former National Football League (NFL) players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) neuropathology at death. The study, published in JAMA Network Open on 28 October 2026, is described by its authors as, to their knowledge, the first population-level estimate of CTE neuropathology among deceased former NFL players.
What CTE is
CTE is a progressive neurodegenerative disease associated with repeated head impacts, such as those from contact sports, military combat, and intimate partner violence. It can only be confirmed after death by examining brain tissue. Cognitive, mood, and behavioural symptoms during life are among the reasons families donate brains for research, and Psychreg has previously explored how head injuries can change a person’s personality.
Dr Yorghos Tripodis, professor of biostatistics at Boston University School of Public Health, said:
“Millions of American men have played tackle football, so knowing how common CTE is among players is an important public health question. We wanted a more precise estimate. That number matters for two reasons. First, it helps the medical community prepare to support players and families dealing with suspected CTE. Second, it gives current and future players accurate information about the risk, so everyone involved can work to make the game safer.”
Why donor-only figures overstate the population burden
Most of what is known about CTE in NFL players comes from brains donated to research. Families are more likely to donate when a player showed cognitive, mood, or behavioural symptoms, so donated brains are not a fair sample of all players. A widely cited 2017 study found CTE in 110 of 111 former NFL players, a figure the new paper says cannot represent the whole NFL population.
To correct for this, the researchers linked brain bank data with national death records covering all 2,362 former NFL players who died in the period, of whom 396 were donors. Among 387 donors with a CTE assessment, 362 (93.5%) had the disease. Players with clear cognitive symptoms were roughly five times more likely to have their brains donated (selection ratio 4.97).
What the adjusted estimate shows
After adjusting for this donation bias, the estimated prevalence of CTE neuropathology among all 2,362 deceased players was 74.5% (95% CI 69.6% to 78.3%). A deliberately cautious lower-bound analysis still gave 63.7% (95% CI 57.2% to 68.9%). The authors’ bias-adjusted estimate of all-cause dementia history during life in the same group was 27.2% (95% CI 22.6% to 31.6%). Even if players with symptoms were 10 times more likely to donate, they write, prevalence would still exceed 60%.
The authors stress important limits. The findings apply only to deceased NFL players and cannot be extended to living or current players, or to people with less exposure to head impacts. The estimate covers all stages of CTE, and many cases may have been early stage and possibly symptom free. Nondonors were assessed using death records and estimates of mild cognitive impairment rather than direct clinical examinations.
Tripodis said:
“Having CTE changes in the brain does not mean every player had symptoms, and we don’t want to cause undue alarm. However, multiple studies, including this one, suggest that former NFL players have four times the rate of dementia that we’d expect to see in the general population at a similar age. No other environmental or occupational exposure ever studied is known to have increased dementia risk at death by that amount. The takeaway for everyday people is that repeated hits to the head carry real long-term risks to the brain. If someone you love played football and is struggling with memory, mood, or behaviour, those symptoms deserve medical attention and support.”
What it means beyond American football
The study does not cover association football, but repeated heading is a live question in the UK. FA guidance recommends that adult amateur players limit heading practice to 10 headers per session, in only one session a week. Research has also looked at simple changes to the ball that could reduce head injury risk, and international experts have issued updated guidelines on athlete concussion care.
Looking ahead, Tripodis said:
“Our top priority is a reliable way to diagnose CTE during life, and we are making real progress in that direction. Once we can diagnose the disease in living people, we can design the clinical trials needed to find effective treatments and, ultimately, a cure. We invite former players to join studies aimed at diagnosing and treating CTE during life. We are also working to understand the risk for people who played only in high school or college, which is where most players’ careers end. Finally, CTE is preventable. Repeated head impacts are the only known risk factor, so we need to limit how often players are hit in the head.”
The authors conclude that selection bias inflates donor-based estimates but is unlikely to fully explain the high burden of CTE neuropathology among deceased former NFL players. They call for research at high school and college levels, and into the mechanisms, symptoms, and prevention of the disease.
