Nearly one in four former NFL players who died between 2016 and 2021 had been diagnosed with chronic traumatic encephalopathy (CTE), according to a study published Tuesday in the British Medical Journal. The findings, which link the neurodegenerative disease to repeated head impacts, suggest the actual prevalence of the condition could be significantly higher among professional athletes.
High Prevalence of Brain Disease
The research, conducted by scientists at Boston University and Harvard Medical School, analyzed 878 NFL players who died during the six-year period from 2016 to 2021. Of those deaths, 215 players—representing 24.5%—were diagnosed with CTE. However, researchers emphasized that this figure is likely a conservative estimate.
Dr. Daniel Daneshvar, chair of physical medicine and rehabilitation at Mass General Brigham and the study’s lead author, stated that the true prevalence could reach as high as 97.7%. This higher potential rate depends on how many players whose brains were not examined after death also carried the disease. According to researchers, the true prevalence likely sits somewhere between the 24.5% and 97.7% range.
The Impact of Head Trauma
CTE is a progressive brain disease characterized by an abnormal buildup of the protein tau. While the disease can only be definitively diagnosed after death, it is associated with various neurological symptoms. These symptoms can include memory loss, impulse control problems, anxiety, depression, and anger issues.
Dr. Daneshvar noted that NFL players specifically face a significantly higher risk of neurodegenerative conditions than the general population. Data shows that NFL players have approximately a four times higher rate of death from neurodegenerative disease compared to the general population, which typically sees a CTE prevalence of less than 1%.
Dementia and CTE Severity
The study also highlighted a strong connection between the severity of CTE and the presence of dementia. Among the brain donors who had CTE, 61.3% had been diagnosed with dementia based on medical records and informant reports. This figure rose to 90.4% for donors diagnosed with Stage IV, the most severe form of the disease.
Researchers noted that dementia was a common occurrence among the study's brain donors. The findings indicate that the severity of CTE at the time of death is significantly associated with dementia in NFL player brain donors.
Industry and Association Reactions
The NFL Players Association (NFLPA), which provides funding for research into CTE and other football-related health issues at Boston University, released a statement calling the study a "sobering reminder" that football carries real risks with lasting consequences for players and families. The organization stated the findings serve as a call to action for the entire football ecosystem to advance research and improve player safety.
In response to the study, an NFL spokesperson stated that the league continuously strives to make football safer through strategies designed to reduce concussions and head impacts. The spokesperson added that the NFL remains committed to providing the community with resources to enhance physical and mental well-being and encouraged former players to seek treatment if they have health concerns.
Preventative Measures and Practice Risks
A significant portion of the head impacts leading to CTE may not occur during NFL games. Dr. Daneshvar explained that the bulk of head impacts experienced by these former players occurred at the collegiate, high school, and even youth levels.
Researchers suggested that prevention efforts should focus on reducing repetitive head impacts—not just concussions—to mitigate risk. Dr. Daneshvar noted that approximately 70% of head impacts occur during practice. He suggested that if the reduction of contact in practices, similar to the measures implemented in the NFL's 2011 Collective Bargaining Agreement, were applied to collegiate, high school, and youth levels, athletes would be significantly better off.
Future Research Directions
While this study provides one of the most informative estimates of the CTE burden in the NFL to date, researchers noted that no single study can fully define the epidemiology of the disease or the exact contribution of professional football to its development.
The researchers identified the next major challenge as quantifying the consequences of repetitive head impacts well enough to inform athletes, clinicians, sporting organizations, and policymakers. This will require long-term recruitment and follow-up of players starting from the onset of their careers, potentially beginning in high school or college football.