A Boston University study estimates that 74.5% of former NFL players who died between 2008 and 2023 had signs of CTE, after researchers adjusted for the greater likelihood that symptomatic players donated their brains. Experts stress that the estimate is not a measure of symptoms among living players and cannot be applied to youth football or other nonprofessional sports. They identify remaining limits, including the players who died without donating their brains, and call for better long-term data and early detection methods. Current research follows players over time and examines possible biomarkers, while NFL rule changes and protective equipment are intended to reduce head impacts. The study supports further investigation, not a new rule or a definitive diagnosis.
TLDR: Researchers estimate that CTE signs appeared in nearly three-quarters of sampled former NFL players after adjusting for donation bias, but the result does not describe living athletes or youth players. Experts say longer follow-up and better measures are needed, and ongoing studies are examining changes over time.
A Boston University study estimates that 74.5% of former NFL players who died during a 15-year period had signs of chronic traumatic encephalopathy, or CTE, in their brains. The estimate draws attention to a serious research question, but it is not a count of living players with symptoms. Experts say the findings support collecting more data and improving ways to detect changes during life.
The study’s practical rationale is clear: better evidence is needed to understand CTE, identify possible early warning signs and guide future research. CTE is a degenerative brain disease associated with repeated blows to the head, and it can only be definitively diagnosed after death. That limitation makes careful long-term study important, while also placing firm limits on what a postmortem estimate can establish.
Researchers examined donated brains from 387 players who died between 2008 and 2023. Those donors were part of a larger group of 2,362 former NFL players who died during those years. Ninety-four percent of the donated brains showed some form of CTE. Because people with cognitive symptoms were estimated to be five times more likely to donate their brains than others, the researchers adjusted for that selection bias and estimated that 74.5% of players had CTE.
That adjusted estimate is not a direct measurement of every former player. CBS News chief medical correspondent Dr. Jon LaPook cautioned that it may be too high and noted that the study measured signs of CTE in brain tissue, not the number of people who experienced symptoms. The distinction matters: a brain finding and a person’s lived symptoms are related questions, but they are not interchangeable measures.
The study builds on data published in The British Medical Journal in August. That earlier estimate ranged from 25% to 98% among former NFL players who died between 2016 and 2021. The wide range reflected uncertainty about whether brain donors represented the broader player population, since donors were more likely to have symptoms thought to be related to CTE.
Dr. Kristen Dams-O’Connor, director of the Brain Injury Research Center at Mount Sinai, said the Boston findings should not be treated as representative of current living athletes. Many of the players whose brains were studied ended their careers long ago. She also said the results cannot be applied to most people who played youth football or to other nonprofessional contact-sport athletes.
The approximately 20,000 NFL players who could have died during the study’s 15-year period but did not are another gap in the evidence, Dams-O’Connor said. The researchers used what she described as strong methods to adjust for selection bias, but that adjustment does not remove every uncertainty. Dr. Jeremy Tanner, a neurology professor at the UT San Antonio Health Science Center, said the study helps show the broader picture and cited a minimum estimate of 20% to 25% after accounting for selection bias. He said that level still makes further research important.
There are also reasons not to treat findings from past generations as a fixed forecast for current players. The NFL has changed rules intended to reduce concussions and introduced protective equipment, including Guardian Caps. Dams-O’Connor said those steps should translate to lower CTE risk for newer generations compared with players from decades ago. The NFL said it continuously works to make football safer, including through strategies to reduce concussions and head impacts.
Jay Alberts, director of the Cleveland Clinic Concussion Center, said research should look for early warning signs rather than assume that changes are undetectable. He suggested studying instrumental activities of daily living, such as driving and balancing a checkbook, because those tasks require both cognitive and motor skills. In people with Alzheimer’s or Parkinson’s disease, such abilities can change five to seven years before diagnosis. Alberts said CTE could be similar, but the excerpt does not establish that this timing applies to CTE.
The practical impact described so far is additional research, not a new rule or compliance program. The report identifies no government mandate, fee, form, enforcement process or deadline. It describes ongoing studies that follow current or former players over time, including a study site at UT Health San Antonio, and research into possible biomarkers linked to CTE. Players involved in those studies are the direct focus; the findings do not establish a general diagnosis or risk figure for youth players or other nonprofessional athletes.
Those limits are part of the plan for sound science: the findings can guide questions without being stretched into claims the data cannot support. Long-term studies may help researchers track changes in the body and brain, and future tools could make it possible to detect changes during life. Tanner said such work may eventually help improve prevention or treatment, but no such outcome is guaranteed by this study. The next necessary steps are continued research and careful review of what the evidence can show; experts are working on the measurements and follow-up needed to clarify the picture.
Ryan Mitchell serves as a Staff Writer for Just Right News, where he anchors the desk for Cyber, Technology Policy, and Digital Sovereignty. In an era where the digital landscape has become as much a battlefield as any physical territory, Ryan provides a critical conservative lens on the forces shaping the future of American innovation and national security. His work is defined by a commitment to the idea that American leadership in the digital age is not just a matter of economic success, but a necessity for the preservation of global liberty.
Born and raised in Austin, Texas, Ryan’s perspective is deeply rooted in the Lone Star State’s tradition of independence and skepticism of centralized authority. Growing up in a city that transformed from a quiet state capital into a global technology hub, he witnessed firsthand the disruptive power of the tech industry. This upbringing instilled in him a firm belief in free-market principles and the necessity of protecting individual liberties from both government overreach and corporate overstep. His Texan background serves as a foundational compass, guiding his reporting toward stories that emphasize national resilience and the preservation of constitutional values in an increasingly virtual world.
Now based in San Francisco, California, Ryan operates from the epicenter of the very industry he scrutinizes. Living and working in the heart of Silicon Valley allows him to provide “boots on the ground” reporting that few conservative journalists can match. He navigates the cultural and political complexities of the Bay Area to bring Just Right News readers an inside look at the boardrooms and coding labs where the next generation of digital policy is forged. For Ryan, being stationed in San Francisco is a strategic choice; it allows him to challenge the prevailing ideological monoculture of the tech elite from within their own backyard, ensuring that the concerns of middle America are represented in the conversation about our digital future.
His beat—Cyber, Technology Policy, and Digital Sovereignty—covers the high-stakes world of data privacy, artificial intelligence, and the infrastructure of the modern web. Ryan is particularly focused on the concept of digital sovereignty, arguing that for a nation to remain truly free, it must maintain control over its own technological destiny and critical infrastructure. He frequently explores how international regulations and domestic policies impact the ability of American firms to compete without sacrificing the privacy or security of their citizens.
Central to his current body of work is his featured series, “The New Cold War.” Through this project, Ryan examines the escalating technological rivalry between the United States and its global adversaries. He delves into the complexities of state-sponsored hacking, the global race for semiconductor dominance, and the ideological struggle to define the rules of the internet. Ryan views this competition not merely as a commercial race, but as a fundamental defense of Western values against authoritarian digital models. Through his rigorous reporting and principled analysis, Ryan Mitchell ensures that the readers of Just Right News stay informed about the invisible forces defining the 21st century, always advocating for a future where technology serves the cause of freedom.