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CTE impacting up to 25% of dead players
A new study published in the BMJ estimates that at least 25% of former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE). Analyzing 235 brain donations from 878 deaths, researchers found CTE in 215 brains and highlighted that most head impacts occurred before players reached the NFL. The study and accompanying editorial call for expanded safety measures in football.
Study: CTE found in at least a quarter of deceased former NFL players
A new study published Tuesday in the journal BMJ estimates that at least one in four former National Football League (NFL) players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE), a degenerative brain disease linked to repeated head impacts.
Researchers examined brain donations from 235 of the 878 former players who died during that period and detected CTE in 215 of those brains—a rate of 91.5 percent among donors. Because not every player donated their brain, the team calculated that at minimum 24.5 percent of all 878 deaths involved CTE, with a maximum estimate of 97.7 percent.
The study, conducted by researchers from Mass General Brigham, Boston University, and the Concussion & CTE Center (also identified as the Concussion & CTE Foundation in some coverage), is described in an accompanying editorial as "one of the most informative estimates to date of CTE burden among former NFL players."
CTE link to dementia and head impacts
Among brain donors diagnosed with CTE, 61.3% met the clinical criteria for dementia before death. Looking from the other direction, 95.5% of donors who had dementia also had CTE pathology. Players with Stage IV CTE, the most advanced form, had a 44% higher risk of dementia compared to those with lower stages.
Lead author Dr. Daniel Daneshvar, chair of physical medicine and rehabilitation at Mass General Brigham and associate professor at Harvard Medical School, told sources that NFL players have "about a four times higher rate of death from neurodegenerative disease than the general population." He also emphasized that most head impacts occurred before players entered the NFL. "The bulk of the head impacts that these former NFL players experienced didn’t occur at the NFL level," he said, noting that many happened during college, high school, and youth football.
CTE is a condition that can only be diagnosed after death. It is characterized by an abnormal buildup of the tau protein and has been linked to contact sports such as football, hockey, and soccer, as well as military blast exposure and domestic violence. Symptoms can include memory loss, impulse control problems, anxiety, depression, anger, difficulty walking, emotional instability, and suicidal thoughts.
Methodology and limitations
The researchers analyzed the total number of NFL deaths between 2008 and 2021, using death certificate data and comparing it to brain donors with confirmed CTE. They narrowed the window to 2016–2021, the period with the highest number of brain donations. Many of the donated brains were analyzed at Boston University and the University of California, San Francisco.
The authors acknowledged limitations, including that not all deaths during the period were captured and that family members may have inaccurately recalled or overstated symptoms when providing medical histories. The study also focused on players from the mandatory plastic helmet era beginning in 1949.
Calls for safer practices
The findings highlight risks from head impacts that begin long before athletes reach the professional level. Daneshvar said that "nearly 70 per cent of head impacts are occurring in practice," and suggested that reducing contact in practices to less than once per week—a measure already implemented in the NFL—could benefit athletes if adopted more broadly. An NFL spokesperson said in response: "The NFL continues aim to make the game of football safer, including by implementing strategies to reduce concussions and head impacts."
In 2011, the NFL and the players' union agreed to a collective bargaining agreement that restricted full-contact practices. The league's current CBA, ratified in 2020 and running through March 2031, limits such practices further. The U.S. Supreme Court in 2016 allowed the NFL's settlement of concussion-related lawsuits with thousands of retired players to proceed.
Researchers urged expanding safety rules and reducing contact during practice at all levels to lower the risk of CTE and other neurodegenerative diseases.
How each outlet told it
Bangkok Post
Framing: Headline uses 'may get brain disease' to project risk onto future NFL players, emphasizing the potential fate of players. It leaves out the study's timeframe and the fact that it's based on deceased players. — Alarmist and serious, with phrases like 'lays bare the extreme toll' and 'can only be confirmed in a post-mortem brain exam'. However, it also includes the authors' limitations and editorial praise, giving a balanced scientific tone.
Facts Included:
Study published Tuesday in BMJ
At least a quarter of NFL players may get brain disease
CTE caused by repeated head impacts, symptoms include trouble thinking, memory loss, difficulty walking, emotional instability, suicidal thoughts
Previously linked to contact sports and military blasts
CTE only confirmed post-mortem
Led by Daniel Daneshvar, Harvard Medical School professor
Studied brains of dead players who played at least one NFL game in mandatory plastic helmet era beginning 1949
Framing: Headline simply states 'CTE impacting up to 25% of dead players' - emphasizes the prevalence of CTE without mentioning the study specifics or the range of estimates. — Measured and clinical, with a focus on the scientific methodology and limitations. Example: 'a significant limitation of that study was that it was done in a population of people who were potentially biased'.
Facts Included:
Study released Tuesday in journal BMJ
At least 1 in 4 former NFL players who died 2016-2021 had CTE
Editorial called it 'one of the most informative estimates to date'
CTE can only be diagnosed after death, symptoms include memory loss, impulse control, anxiety, depression, anger
CTE marked by abnormal buildup of protein tau
Previous study found CTE in 99% of NFL player brain donors, with limitation of potential bias
Researchers used death certificate data and compared to brain donors
Study period narrowed to 2016-2021 when highest number of brain donations
878 deaths, 235 donated brains, 215 diagnosed with CTE
Brain banks at Boston University and UCSF
NFL spokesperson quote
Lead author Dr. Daniel Daneshvar, chair of physical medicine and rehabilitation at Mass General Brigham and associate professor at Harvard Medical School
Daneshvar: 'about a four times higher rate of death from neurodegenerative disease than the general population'
Daneshvar: bulk of head impacts occurred at collegiate, high school, youth levels
2011 CBA limited contact practices; current CBA ratified 2020 runs through March 2031
Ivy League banned full-contact tackling in practices five years later
U.S. Supreme Court cleared NFL concussion settlement in 2016
Daneshvar quote about propagating reduced contact practices
Daneshvar: 'nearly 70 per cent of head impacts are occurring in practice'
Framing: Headline emphasizes the four times higher neurodegenerative death rate, which is a secondary finding in the study, rather than the CTE prevalence. It leaves out the study's timeframe and the fact that it's based on deceased players. — Measured and straightforward, with a hint of alarm in 'highlight risks'. The tone is supported by direct quotes and a neutral description of the NFL's response.
Facts Included:
Study released Tuesday
At least one in four former NFL players who died 2016-2021 had CTE
Examined 235 brain donations out of 878 deaths, detected CTE in 215
CTE can only be definitively diagnosed after death
CTE linked to repeated blows to head, causes memory problems, dementia, mood disorders, headaches
Daniel Daneshvar, lead author, said 'about a four times higher rate of death from neurodegenerative disease than the general population'
Findings highlight risks from head impacts beginning before NFL
Daneshvar quote: bulk of head impacts occurred during college, high school, youth football
NFL spokesperson quote: 'continuously strives to make the game of football safer'
Researchers called for further reductions in contact during practices across all levels
Framing: Emphasizes the finding that 1 in 4 former NFL players had CTE, and adds the context of the study period (2016-21). Does not mention the study's method or the broader ranges of estimates. — Measured and factual, with a concern for safety. Supported by quotes like 'If the changes... were propagated... athletes would be better off' and describing the 91.5% positivity as 'whopping'.
Facts Included:
Study published Tuesday in BMJ
Conducted by Mass General Brigham, Boston University, Concussion & CTE Center
878 former players died 2016-2021, 235 brains donated, 215 tested positive for CTE
25% of former NFL players who died had CTE
61.3% of CTE donors met clinical criteria for dementia
95.5% of donors with dementia had CTE pathology
Stage IV CTE had 44% higher risk of dementia
Daniel Daneshvar quoted: 'bulk of the head impacts... didn't occur at the NFL level'
Each row is one claim, attributed to the outlet whose wording states it most clearly. Confidence rates how directly the source text states the claim — explicit and unhedged rates high; hedged, pieced-together, or internally inconsistent statements rate lower. It does not measure whether the claim is true. Status counts the distinct outlets we found asserting it — so a single-source claim can still show high confidence, and a multi-source claim can show medium. Every one of those outlets is named beside the status, so you can check the count against the list. For claims extracted before we began storing that list, the row says so: it names the outlet the claim is quoted from and states that we have not recorded which outlets backed it. Outlets wrote at different times, so a figure that evolves — a casualty count, for example — can legitimately differ between rows; check the "as of" time next to each claim's source.
Claim
Confidence
Status
ClaimAt least 25% (or 1 in 4) of former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE).
ClaimThe study was conducted by researchers from Mass General Brigham, Boston University, and the Concussion & CTE Center (also named as Concussion & CTE Foundation in another source).
ClaimDaniel Daneshvar, lead author and associate professor at Harvard Medical School, said the bulk of head impacts experienced by former NFL players occurred at the collegiate, high school, and youth levels, not at the NFL level.
ClaimAn NFL spokesperson said: 'The NFL continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts.'
ClaimIn 2011, the NFL and the players' association agreed to a Collective Bargaining Agreement that significantly restricted full-contact practices.
ConfidenceHigh
StatusMulti-source (2 outlets) via ThePrint , CP24
ClaimDaniel Daneshvar told The Guardian that if changes implemented at the NFL level, including reducing contact in practices to less than once per week, were propagated at collegiate, high school, and youth levels, athletes would be better off.
ConfidenceHigh
StatusMulti-source (2 outlets) via ThePrint , CP24
ClaimResearchers and health experts urged expanding safety rules and reducing contact practices to lower the risk of degenerative brain disease.
ClaimThe study is 'one of the most informative estimates to date of CTE burden among former NFL players', according to an editorial that published along with the study.
ClaimSymptoms of CTE can include memory loss, impulse control problems, anxiety, depression, anger issues, trouble thinking, difficulty walking, emotional instability, and suicidal thoughts.
ClaimCTE is most often seen in people who play sports such as football, hockey and soccer, but has also been detected in soldiers exposed to explosions and in some people who experienced domestic violence.
ClaimThe previous 99% study had a limitation: it was done in a population of people whose brains were donated by family members who may have noticed symptoms while living.
ClaimFor the new study, researchers analyzed the total number of NFL deaths between 2008 and 2021, using death certificate data and comparing it to the number of brain donors with confirmed CTE.
ClaimDaniel Daneshvar is the chair of physical medicine and rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School.
ClaimThe study authors wrote that NFL players have a higher prevalence of CTE at death than has been previously shown in multiple community-based studies.
ClaimThe study authors acknowledged limitations: not all former NFL players who died during the study window were included, and some family members may have inaccurately recalled or over-stated symptoms.
ClaimProfessors Tobias Kurth of the University Medical Center Berlin and Richard Riley of the National Institute for Health and Care Research in Birmingham praised the study design in a related editorial.