Summary:
A multi-institutional analysis led by researchers at Boston University estimates that roughly three out of four National Football League (NFL) players who died between 2008 and 2023 showed chronic traumatic encephalopathy (CTE) neuropathology on postmortem examination. Published in JAMA Network Open, the study corrected for donation-related selection bias by linking brain bank findings to National Death Index records for 2,362 deceased players, yielding an adjusted prevalence of 74.5%. This contrasts sharply with community brain bank series, where CTE is identified in under 1% of donors.
Key Facts:
- Population-Level Prevalence: After accounting for selection bias across all 2,362 NFL players who died from 2008 through 2023, the model estimates a postmortem CTE prevalence of 74.5%.
- Correcting for Donation Bias: Families of players who experienced cognitive or neurobehavioral symptoms were about five times more likely to donate brains for research, allowing biostatisticians to adjust the raw 93.5% pathology rate seen in the brain bank down to a representative population estimate.
- Marked Difference from General Population: Community brain banks from multiple countries report CTE in less than 1% of donors, emphasizing the elevated risk associated with repetitive head impacts in contact sports such as professional football.
Source: Boston University School of Public Health
Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative tauopathy linked to repetitive head impacts. Because a definitive CTE diagnosis currently depends on postmortem tissue examination to identify perivascular clusters of hyperphosphorylated tau, estimating true disease prevalence among professional athletes has long been complicated by selection bias: families of players with severe symptoms are more likely to donate brains to research.
To address that limitation, a collaborative team from the Boston University School of Public Health, Boston University Chobanian & Avedisian School of Medicine, Mass General Brigham, and the Concussion & CTE Foundation combined detailed neuropathological evaluations with comprehensive mortality records to produce the first population-wide estimate of CTE prevalence for an era of professional football.
Published in JAMA Network Open, the study reports that 74.5% of former NFL players who died between 2008 and 2023 had neuropathological evidence of CTE.
Overcoming the Selection Bias Dilemma
Previous estimates of CTE prevalence among NFL players varied widely because brain donors are not a random sample of all deceased players. In an earlier analysis by the same group, prevalence estimates ranged from 25% to 98% for players who died between 2016 and 2021, reflecting uncertainty about how representative brain bank donors were of the broader player population.
To generate a more accurate estimate, investigators developed a biostatistical model that integrated direct tissue diagnoses from the brain bank with National Death Index data for all 2,362 players who died between 2008 and 2023. Among 387 players whose brains underwent neuropathological examination, 362 (93.5%) had CTE. The team then compared donor and non-donor groups across demographic characteristics, playing position, career duration, age at death, causes of death, and documented clinical diagnoses such as dementia.
Those comparisons showed that former players with cognitive or neuropsychiatric symptoms were roughly five times more likely to have brain tissue donated than players without such symptoms. Applying that selection ratio across the entire cohort, the model produced the adjusted population prevalence of 74.5%.
“Providing a precise estimate for CTE prevalence among deceased NFL players helps clarify the scale of the problem and guides planning for current and future clinical needs,” said lead author Julia Gallini, a PhD candidate at the Boston University School of Public Health. “With CTE detected in under 1% of community brain bank donors, an estimated 75% prevalence among NFL decedents across a 16-year period is alarming. These results underscore the need to support families, improve ante-mortem diagnosis, and develop treatments for CTE-related symptoms.”
Contextualizing Risk and Symptom Expression
The authors emphasize that the 74.5% estimate applies only to deceased former NFL players within the specific 2008–2023 window and should not be extrapolated directly to living retirees or active players, who may have experienced different protective equipment, concussion protocols, or career exposures.
Importantly, postmortem evidence of CTE pathology does not necessarily indicate that an individual had clinically apparent impairment during life, particularly in early stages of the disease. When symptoms do occur, they often include progressive cognitive decline, executive dysfunction, mood instability, and dementia. Prior epidemiologic research has shown that former NFL players develop clinical dementia at substantially higher rates than the general population, a risk elevation associated with repeated head trauma.
“It’s difficult to fully grasp what many of the players who built the modern game have endured,” said Matt Hasselbeck, an 18-year NFL veteran and DIAGNOSE CTE study ambassador. “This research gives us a clearer picture of the challenge. I can’t undo the hits I took, but I can help advance research that aims to prevent and treat these conditions for future generations.”
The Path Toward In Vivo Diagnosis and Intervention
Senior author Yorghos Tripodis, PhD, professor of biostatistics at the Boston University School of Public Health, noted that accurately defining the scope of CTE motivates clinical and research efforts to improve diagnosis and care.
“We appreciate the support of the former NFL player community for research that addresses the link between tackle football and CTE,” said Dr. Tripodis. “We understand this information may raise concerns for living players and their families. Researchers and clinicians remain committed to offering support and advancing work that moves toward reliable in vivo diagnosis and, ultimately, effective treatments.”
Clinical specialists recommend that former athletes who experience new or worsening mood, memory, or behavioral symptoms seek evaluation from clinicians skilled in neurodegenerative disorders. Early management of vascular risk factors, sleep disorders, metabolic conditions, and psychiatric symptoms can help preserve cognitive function and improve quality of life.
Funding
This research was supported by the National Institute on Aging Boston University Alzheimer’s Disease Research Center (P30AG072978), the National Institute of Neurological Disorders and Stroke (U54NS115266), and the Concussion & CTE Foundation.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The full journal article will be reviewed when it is publicly released.
- Additional context was provided by staff editors.
About this CTE Research:
- Media Contact: Gina DiGravio
- Source: Boston University School of Medicine
- Image Credit: Image credited to Neuroscience News
- Original Research is Open Access: The findings will appear in JAMA Network Open
