Contact Sports and Football
What a New Study Reveals About Traumatic Brain Injuries
By Thomas Lehrich, Vanessa Souders, and Kevin Johnston, NP | Plus One Foundation
Abstract: Brain research is one of the last frontiers in medical research. Plus One Foundation's education campaign Think aBout It features educational information and outreach on contemporary neurological topics. Education is at the heart of what we do—our Think aBout It campaign aims to dig deeper into all aspects of TBIs and neurological conditions.
American football is celebrated for its physical intensity, teamwork, discipline, and competitive spirit. Like other contact sports, the long-term consequences of repeated blows to the head of athletes are subject to a new study.
A newly published study by JAMA Network Open brings this issue into sharper focus. Researchers from Boston University, Mass General, and the Concussion & CTE Foundation examined the brains of 2,362 former National Football League (NFL) players and estimated that approximately 74.5% had chronic traumatic encephalopathy (CTE) when they died. In comparison, the National Death Index reports CTE to be present in less than 1% of typical deaths. The brains were from players that had died between 2008 and 2023.
The findings extend beyond professional football. They raise important questions about the cumulative effects of repeated head impacts, the adequacy of existing player protections, and the responsibility of sports organizations to safeguard athletes’ health long after their playing careers end. This is not just football, but any sport that involves repeated blows to the head. This includes soccer, boxing, hockey, martial arts, auto racing, and cycling.
Understanding the Impact of Repeated Head Trauma
Football, hockey and other collision sports expose players to impacts that can injure the brain. While concussions are an important and widely recognized consequence of these collisions, researchers have become increasingly concerned about the cumulative effects of repeated head impacts, including those that do not produce immediately recognizable concussion symptoms.
One condition associated with repetitive head trauma is chronic traumatic encephalopathy, or CTE. This progressive neurodegenerative disease is characterized by abnormal accumulations of tau protein and other changes in brain tissue. It has been associated with difficulties involving memory, thinking, behavior, mood, and emotional regulation. The severity is staged as levels I through IV, with IV being the worst. Very few symptoms are noted in the early stages, but it is an insidious disease, accelerated by repeated head traumas.
Currently, CTE can only be definitively diagnosed by examining brain tissue after death. Consequently, scientists have faced a major challenge in determining how common the disease is among living and retired football players. Many of the brains available for research have come from families who chose to donate them because their loved ones experienced concerning neurological or behavioral symptoms. This creates a potential selection bias: donated brains may disproportionately represent individuals with suspected brain disease. The families donated these brains because they were concerned about behavioral changes that they may have noticed, even if there were no formal medical diagnoses.
What the New Study Found
The study, led by researchers affiliated with Boston University's Alzheimer’s Disease Research Center and CTE Center, analyzed medical records from 2,362 former NFL players who died between 2008 and 2023. These players had spent an average of five years in the league. Nearly 400 had donated their brains for scientific examinations.
Among those brain donors, approximately 93.5% showed evidence of CTE. Although this figure is alarming, it cannot automatically be applied to every former NFL player because brain donors may have been more likely to experience symptoms that prompted their families to participate in research.
To address this limitation, researchers used medical records from both donors and nondonors to estimate the likely prevalence of CTE across the larger group. They found that former players with documented cognitive symptoms were approximately five times more likely to donate their brains. After adjusting for this difference, the researchers estimated that 74.5% of the deceased former NFL players in the study had CTE pathology at death.
The study’s senior author Yorghos Tripodis, PhD, a professor of biostatistics at Boston University, emphasized the magnitude of the estimated dementia-related risk. However, the result should be understood as a statistical estimate derived from a model, not a direct brain examination of every player in the study.
Russell Lonser, a professor of neurological surgery at The Ohio State University who was not involved in the research, described the work as an important effort to correct for selection bias in brain-bank data while cautioning that the findings remain an estimate.
Why These Findings Matter
The study's significance extends well beyond professional football. It adds to growing concerns about how repetitive head impacts may affect the brain over time and highlights the need to take neurological health seriously in contact sports.
For players, the potential consequences can extend well beyond their final game. Cognitive difficulties, emotional changes, memory problems, and other neurological symptoms can affect relationships, employment, independence, and overall quality of life. Families may also shoulder the emotional and practical burdens of caring for loved ones experiencing these challenges. The NFL, college and high school football team owners and management have taken note of these reports and are actively developing safer equipment (such as helmets that absorb more of the impact and softer turf) and rules to reduce helmet-on-helmet contact and other hard hits.
For the medical community, the findings reinforce the importance of investigating the long-term effects of repeated head trauma. Researchers need better ways to identify individuals at risk, understand how brain injuries develop, and distinguish CTE-related symptoms from other conditions that can cause dementia or behavioral changes.
The study also highlights a critical limitation: researchers examined former players who had died, so the findings do not establish the prevalence of CTE among current NFL players or provide a precise estimate of any individual player's risk. CTE was first described in 1928 by Dr. Harrison Martland as being 'punch drunk' from boxing. Boxing has also introduced safety protocols to reduce the damaging effects. Other sports, such as cycling and skateboarding, have added helmets and tried to reduce exposure to CTE-inducing contact. Soccer also has been implicated as a major source of CTE cases.
The Challenge of Diagnosing CTE
One of the greatest obstacles in addressing CTE is the absence of a definitive diagnostic test for living individuals. Although researchers can identify characteristic brain changes through postmortem examination, they cannot yet establish a definitive diagnosis of CTE in a living athlete.
This creates a difficult situation for former players and their families. Symptoms such as memory loss, depression, irritability, mood changes, and cognitive difficulties can overlap with those associated with Alzheimer's disease, other neurological disorders, and psychiatric conditions.
This uncertainty matters. Not every former football player who experiences memory loss, depression, or mood changes has CTE. Similarly, the absence of an established diagnosis does not mean that repeated head impacts are harmless.
The new study reinforces the importance of developing reliable diagnostic tools, identifying potential indicators of neurological disease, and understanding how brain changes evolve over time.
Progress in these areas could eventually allow healthcare professionals to identify individuals at greater risk, provide earlier interventions, and better support athletes experiencing neurological difficulties.
What This Means for Football Safety
The NFL has introduced various measures intended to reduce head injuries, including changes to playing rules, concussion recognition, and return-to-play protocols.
These efforts are important. However, the new findings raise a broader question: Are existing protections sufficient to address the cumulative effects of repeated head impacts?
A major concern is that reducing diagnosed concussions alone may not adequately address the problem. Athletes can experience repeated head impacts without necessarily sustaining a concussion or displaying immediate symptoms.
Consequently, prevention efforts must look beyond the treatment of diagnosed concussions and consider the broader burden of repetitive head trauma.
Several areas deserve continued attention:
• Safer playing techniques: Coaching methods and tackling practices should continue to evolve to minimize unnecessary head contact.
• Improved equipment: Protective equipment should be continually evaluated and improved, while recognizing that helmets alone cannot eliminate the risk of brain injury.
• Stronger medical oversight: Athletes need appropriate medical evaluation, transparent concussion management, and carefully monitored return-to-play decisions.
• Reduced exposure: Sports organizations should examine whether practice structures, training methods, and playing rules can reduce unnecessary repetitive head impacts.
• Long-term monitoring: Neurological health should remain a priority after retirement, not simply during an athlete's active career.
Youth and amateur football deserve particular attention.
Children and adolescents are still developing, and their participation in contact sports raises questions about how best to balance the benefits of physical activity, teamwork, and competition with the potential neurological risks.
Parents, coaches, schools, and sports organizations must have access to accurate, evidence-based information. No single intervention can eliminate every risk. But prevention, education, medical oversight, and continued scientific research can help reduce avoidable harm.
Moving Forward: Awareness, Prevention, and Accountability
This study represents an important contribution to the growing body of evidence concerning repetitive head trauma and long-term brain health. It also demonstrates why researchers must carefully account for selection bias when studying diseases that can only be confirmed after death.
Several priorities emerge from these findings:
• Invest in research: Support efforts to understand the mechanisms, progression, and long-term consequences of repetitive head impacts.
• Improve prevention: Continue evaluating playing rules, tackling methods, equipment, and training practices to reduce unnecessary head trauma.
• Strengthen medical care: Ensure that athletes receive timely assessment and appropriate follow-up when they experience concussions or neurological symptoms.
• Educate families and communities: Provide balanced, evidence-based information so athletes and families can make informed decisions.
• Support former players: Improve access to neurological evaluation, mental health services, rehabilitation, and long-term care as needed.
These priorities require cooperation among researchers, healthcare providers, athletic organizations, schools, coaches, and families. Protecting athletes cannot be the responsibility of any single group.
Ultimately, the goal should not be to create unnecessary fear or to dismiss the value of sport. It should be to ensure that athletes understand the risks, receive appropriate protection, and have access to the care and support they need throughout their lives.
Conclusion
The findings published in JAMA Network Open are a reminder that the consequences of contact sports and football can extend far beyond the playing field.
The estimated prevalence of CTE among the deceased former NFL players studied underscores the importance of continued scientific investigation, better prevention strategies, improved diagnostic technologies, and long-term support for athletes.
Important uncertainties remain. Researchers still need to understand how CTE pathology translates into clinical symptoms, why some individuals are more vulnerable than others, and how repetitive head impacts influence neurological health over a lifetime.
But uncertainty should not become an excuse for inaction. Athletes dedicate enormous amounts of time, energy, and physical effort to the sports they love. They deserve advancing scientific knowledge to make the sport safer.
Football and other athletics offer tremendous value to individuals and communities. The challenge now is to turn awareness into action, research into progress, and accountability into lasting change.
The Role of the Plus One Foundation
Plus One Foundation mobilizes resources to inspire hope and enrich the lives of those affected by neurological conditions and educate the community about related issues.
At Plus One Foundation, we provide programming and education for individuals with neurological conditions. Our programming in movement therapy, aquatics and music helps the neurological community with recovery.