TL;DR
Get sports gear delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
A study in JAMA Network Open estimates that about 75% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE). The estimate adjusts for likely donation bias, but CTE can currently be confirmed only after death, and the finding does not mean that three-quarters of players had dementia or symptoms.
A study published Wednesday in JAMA Network Open estimates that about 75% of former NFL players who died from 2008 to 2023 had signs of chronic traumatic encephalopathy, or CTE. The figure is a statistical estimate—not a diagnosis of every player in the group—and researchers say CTE can currently be confirmed only through examination of the brain after death.
The research team combined findings from 396 donated brains held by Boston University’s UNITE Brain Bank with records on 1,966 other deceased former NFL players. The combined group represented about 2,360 players who died during the 15-year period. Researchers estimated that approximately 1,760 players had CTE.
Signs of CTE were found in about 93% of the donated brains, but brain-bank donations are not a representative sample of all former players. Families of players who had cognitive symptoms were estimated to be about five times more likely to donate a brain than families of players without such symptoms. The researchers used statistical adjustments intended to account for that imbalance.
The study also estimated that about 27% of the players had dementia. That is a separate measure from the estimated rate of CTE: the researchers said the dementia estimate includes dementia from all causes. CTE-related changes do not necessarily lead to noticeable symptoms, cognitive decline or dementia.
What the Estimate Says About CTE
The estimate offers a broader view than research based only on donated brains, which can overrepresent people whose families sought an examination because of symptoms. It also underscores the difficulty of measuring CTE in living people: the headline figure may help researchers frame the scale of the issue, but it cannot establish how many current or former players have symptoms caused by the disease.
CTE is associated with repeated head impacts, and the findings keep attention on the long-term health questions surrounding football. They do not, by themselves, establish that every player with CTE had cognitive or behavioral problems, or that CTE caused a particular player’s symptoms. The distinction matters for families, clinicians and league safety discussions, since the brain changes and a person’s daily functioning are not interchangeable measures.
Products Worth Considering
Therabody Theragun Prime 6th Generation Deep Tissue Massage Gun, Black
Coleman Sundome 6-Person Camping Tent with Rainfly
Garmin Tacx Antares Indoor Bicycle Rollers, 62 cm
As an affiliate, we earn on qualifying purchases.
How Researchers Adjusted Donation Bias
Researchers have previously reported high CTE rates among donated brains, but those collections are subject to selection bias. A Boston University study cited in the report found signs of CTE in 99% of brains donated for research by former NFL players. That figure describes the donated sample, not all former players.
In an earlier study published in August, the same research group estimated that one-quarter of NFL players who died in a five-year span had CTE. The new analysis covers a longer period and uses brain-bank findings alongside death records and estimates of mild cognitive impairment and dementia among former players over 50. The researchers’ adjustment aims to address donation bias, but it does not replace examinations of every person in the population.
CTE involves structural changes in the brain associated with repeated head impacts. According to neurosurgeon Julian Bailes, impacts can cause the brain to move within the skull, and repeated injury can contribute to the accumulation of tau proteins. Symptoms associated with CTE can overlap with those of other conditions, including dementia and Parkinson’s disease.
““Right now we don’t know how to diagnose CTE when people are alive, so we are trying to estimate.””
— Yorghos Tripodis
What the Study Cannot Confirm
The study does not establish a precise, individually confirmed CTE count for the estimated 2,360 players. Most players in the analysis did not have donated brains examined, and the researchers used statistical methods to infer prevalence from available data. The estimate depends on those methods and assumptions about donation patterns and cognitive conditions.
CTE is currently diagnosed through examination of brain tissue after death, not through a definitive test in a living person. It is also unclear how many people with the brain changes will develop symptoms. Some lesions found at autopsy may be limited, and symptoms such as memory loss, depression or changes in behavior can have other causes. The study’s estimated dementia rate includes all causes, so it cannot show what share of dementia in the group was caused by CTE.
Prevention and Diagnosis Research
The study does not announce a new diagnostic test or a change in NFL rules. Researchers and outside experts cited in the report said better methods for identifying CTE in living people are needed. Until such methods exist, prevalence research will continue to rely on brain examinations after death and statistical estimates that account for who is more likely to donate.
Tripodis said reducing brain injuries and impacts is a key prevention approach. The NFL spokesperson pointed to measures including redesigned helmets, such as the Guardian Cap, and a dynamic kickoff rule intended to lower collision speeds. The study does not assess the effectiveness of those measures. Follow-up research will be needed to clarify how well safety changes reduce impacts and how CTE-related brain changes relate to symptoms over time.
Key Questions
What does the 75% estimate mean?
Researchers estimated that about 1,760 of roughly 2,360 former NFL players who died between 2008 and 2023 had CTE. It is a population estimate based partly on donated-brain findings, not an autopsy-confirmed result for every player.
Does the study say 75% of former players had dementia?
No. The study estimated that about 27% of the players had dementia. That estimate covers dementia from all causes, and the study did not establish that all of it was caused by CTE.
Can doctors diagnose CTE in a living person?
According to the researchers and experts quoted in the report, CTE can currently be diagnosed only by examining brain tissue after death. There is no established way to confirm it in a living person.
Why was the rate among donated brains higher?
Brain donations may overrepresent players who had symptoms. The study estimated that families of players with cognitive decline were about five times more likely to donate than families of players without symptoms, and researchers adjusted their estimate to account for that bias.
What did the NFL say about the findings?
An NFL spokesperson said the league works to make football safer and cited efforts to reduce concussions and head impacts. The statement did not address the study’s specific prevalence estimate.
Source: nbcnews.com
