A major 2026 study has renewed attention on CTE in former NFL players. Published in The BMJ in August, the research examined chronic traumatic encephalopathy among former professional football players who died between 2008 and 2021.
The findings are important, but they also require careful explanation. One headline number can easily create the wrong impression.
Researchers examined the brains of 338 former NFL players. CTE was found in 315 of those donors, or 93.2%.
That does not mean researchers proved that 93.2% of all former NFL players develop CTE.
Most players who died during the study period did not donate their brains. Brain donation can also be influenced by symptoms, family concerns, and other factors. The researchers therefore used a wider approach to estimate what the findings might mean across the deceased NFL population.
This article explains the study, its connection with dementia, and the limits readers should understand before turning the results into a simple statistic.
What the 2026 Study Found About CTE in Former NFL Players
The researchers identified 1,712 former NFL players who died between 2008 and 2021. All had played in the era after hard-shell helmets became standard in professional football.
Of those 1,712 players, 338 donated their brains for neuropathological examination. That represented about one in five of the deceased players in the study group.
Neuropathologists examined the donated brains without knowing the players’ clinical histories. Clinicians also reviewed medical records and information from people who knew the players. Those clinicians did not know the brain findings when deciding whether dementia had been present.
This type of blinding helps reduce the risk that one set of findings influences how researchers interpret another.
Why the Study Did Not Report One Simple CTE Prevalence Number
Among the 338 brain donors, 315 had CTE pathology. That equals 93.2% of the donated brains.
However, the researchers did not have brain tissue from the other 1,374 former players who died during the same period.
Without those brains, researchers could not determine whether each non-donor had CTE.
Instead, the study calculated a possible range.
The lowest estimate assumed that only the confirmed donor cases had CTE. Under that very conservative assumption, 18.5% of all 1,712 deceased players had CTE.
The highest estimate assumed that almost every unexamined player also had CTE. That produced an upper estimate of 98.7%.
The wide range shows how much uncertainty remains when tissue is unavailable for most members of a population.
Why the 93.2% Brain-Donor Figure Is Not the General NFL Prevalence
Brain banks do not receive a random sample of every person who dies.
A family may be more likely to donate a brain when a former athlete experienced memory problems, behavioral changes, dementia, or other neurological concerns. Players without noticeable problems may be less likely to become brain donors.
That creates what researchers call selection bias.
The BMJ study tried to address this problem in several ways. Most importantly, it identified the larger population of NFL players who died during the study period instead of studying only the brain-bank group.
Still, researchers could not determine the exact CTE status of players whose brains were never examined.
That is why saying “93% of NFL players have CTE” would go beyond what this study established.
A more accurate statement is that 93.2% of the examined brain donors had CTE, while the exact prevalence among all deceased former NFL players remained uncertain.
That distinction is central to reading brain-bank studies responsibly.
The Later Study Period Provides a Stronger Minimum Estimate
Brain donation became more common during the later years of the study.
From 2016 through 2021, 878 former NFL players in the study population died. Researchers examined the brains of 235, or 26.8%.
CTE was confirmed in 215 of those donors.
Even if every unexamined player were assumed not to have CTE, those confirmed cases alone equal 24.5% of all former NFL players who died during that six-year period.
That is why the authors concluded that, at minimum, nearly one-quarter of former NFL players who died during 2016–2021 had CTE pathology at death.
The estimate still applies to the deceased players studied. It should not be automatically extended to every current or former NFL player alive today.
Questions about exposure also remain important. Years of contact-sport participation, number and intensity of head impacts, age, medical history, genetics, and other factors may all shape long-term risk.
Readers interested in why modern brain-injury science is moving away from simple labels can also read our guide to the newer multidimensional TBI classification framework.
More Severe CTE Was Associated With Dementia Among Brain Donors
The study also looked at the relationship between CTE severity and dementia.
Researchers classified CTE pathology by stage. Stage I represents less extensive pathology, while stage IV represents the most advanced stage.
Among the 338 donors, 104 had stage IV CTE.
Overall, 202 donors had dementia based on the study clinicians’ review of records and histories. Dementia was particularly common among donors with stage IV disease.
After statistical adjustment, stage IV CTE was associated with a 44% higher risk of dementia compared with donors who did not have stage IV CTE.
This finding strengthens evidence that advanced CTE pathology can have meaningful clinical consequences.
It does not mean CTE was the only possible contributor to dementia in every donor.
Many people had more than one form of brain disease. Some also had Alzheimer’s disease, Lewy body disease, frontotemporal degeneration, or other neuropathological findings.
CTE Can Still Be Confirmed Only After Death
One of the most important facts about CTE is also one of the most easily misunderstood.
CTE remains a neuropathological diagnosis. At present, it can be confirmed only by examining brain tissue after death.
Researchers look for a characteristic pattern involving abnormal phosphorylated tau protein around small blood vessels in particular areas of the brain.
Scientists are actively studying blood tests, imaging, and other biomarkers that might eventually help identify CTE during life. Those tools are not yet able to provide a definitive diagnosis.
Researchers use the term traumatic encephalopathy syndrome, or TES, for a proposed clinical syndrome associated with substantial repetitive head-impact exposure and progressive cognitive or behavioral problems.
However, TES and confirmed CTE are not interchangeable.
A 2026 Nature Medicine study highlighted this challenge. Researchers tested current TES criteria against postmortem findings and found that the criteria still have limited ability to identify exactly who has CTE pathology.
That uncertainty is one reason symptoms should be evaluated medically instead of being self-diagnosed as CTE.
What the New CTE Research Means—and What It Does Not Mean
The 2026 BMJ study adds important information to a difficult research problem.
Previous brain-bank studies showed high rates of CTE among donated brains from former professional football players. Critics correctly noted that brain donors could differ from the entire football population.
The new study improves on that approach by identifying all former NFL players who died during a defined period. It then places confirmed brain-donor cases inside that larger group.
This method still cannot produce one exact prevalence figure. However, it gives researchers a stronger lower boundary for how common CTE was among the deceased players studied.
It also provides further evidence that severe CTE pathology is associated with serious cognitive outcomes.
Repetitive Head Impacts Matter More Than One Concussion Story
CTE research increasingly focuses on cumulative exposure to repetitive head impacts.
That includes diagnosed concussions, but it can also include repeated impacts that never produce obvious concussion symptoms.
This distinction matters because CTE should not be reduced to a simple question such as how many diagnosed concussions a person had.
American football players can experience hundreds or thousands of head impacts across years of practices and games. The force of those impacts also varies widely.
Researchers continue to study how duration of play, position, impact intensity, age of first exposure, and other factors relate to later brain changes.
The BMJ study found that longer lifetime football participation was associated with advanced CTE severity among donors.
However, population research cannot predict the future of one individual athlete.
Our return-to-sports after concussion guide explains why current concussion care focuses on recognizing an injury, removing the athlete from danger, and returning gradually under appropriate medical supervision.
Symptoms After Football Do Not Automatically Mean CTE
Memory problems, depression, irritability, headaches, sleep problems, balance changes, and difficulty concentrating can occur for many reasons.
Some can follow brain injury. Others may relate to depression, sleep disorders, medication effects, cardiovascular disease, chronic pain, substance use, Alzheimer’s disease, or another neurological condition.
A history of football or repetitive head impacts therefore does not make every later symptom evidence of CTE.
That point is especially important because people may become frightened after reading a study about former professional athletes.
Someone with new or worsening cognitive, behavioral, balance, or neurological symptoms should receive an appropriate medical evaluation. Clinicians can look for treatable conditions and assess the full health history rather than assuming one explanation.
Likewise, this study should not lead every former football player to expect dementia.
The data describe risk and pathology in a specific group of deceased professional athletes. They do not provide an individual prediction for a current player, a former amateur athlete, or someone who experienced one concussion.
Our article on whether traumatic brain injury should sometimes be viewed as a chronic condition explores the wider shift toward following brain health over the long term without assuming that every injured person will develop lifelong problems.
professional athletes.
The central message from the new research is more careful than many headlines suggest.
CTE was common among the examined brains of former NFL players. Even under a highly conservative assumption, confirmed cases represented nearly one-quarter of all former NFL players who died during 2016–2021.
Advanced CTE was also associated with dementia among donors.
At the same time, researchers still cannot give one precise percentage for all former NFL players. They also cannot diagnose CTE definitively in a living person or use this study to predict one athlete’s future.
That combination of evidence and uncertainty is not a weakness of science. It is an accurate description of where CTE research stands in 2026.
Future studies need better ways to follow athletes during life, measure repetitive head-impact exposure, identify reliable biomarkers, and connect clinical changes with eventual neuropathology.
For now, the BMJ study adds an important piece to the evidence that repetitive head impacts can have long-term neurological consequences. It also shows why CTE research needs careful language. Strong findings deserve attention, but they become less useful when uncertainty is removed from the story.
Medical note: This article is for general educational purposes only. It does not diagnose CTE, dementia, concussion, or any other neurological condition. New, worsening, or concerning cognitive, behavioral, physical, or neurological symptoms should be discussed with a qualified healthcare professional.