New research on donated brain tissue from former professional players has reignited discussion about chronic traumatic encephalopathy (CTE) and its prevalence. A study published Aug. 25 in The BMJ examined 338 brains donated by players who died between 2008 and 2021. Within that donor sample, more than 93% showed pathological signs associated with CTE and roughly 30% met criteria for stage IV, the most advanced category identified by neuropathologists.
The authors used the donor sample to estimate possible CTE prevalence across 1,712 former players who died in the same interval, producing a very wide range of estimates. For the entire period the study reported a possible prevalence between about 18.5% and 98.7%; focusing on the period with the most donations (2016–2021) yielded a narrower—but still broad—range of 24.5% to 97.7%. The analysis also found that not all brains with CTE pathology had documented clinical dementia: about 60% of cases with CTE-related changes had a dementia diagnosis, while around 90% of stage IV cases did.
Thayne Munce, director of the Jayhawk Athletic Performance Laboratory at the University of Kansas, who was not involved in the work, emphasized limits that affect interpretation. Donor samples can be biased if people with symptoms are more likely to donate, and the cohort studied largely reflects athletes who played several decades ago. Changes in equipment, rules, practice patterns and formal concussion management mean those historical rates do not necessarily describe risks for current football players, Munce noted in an interview about the study.
The study underscores two distinct findings: neuropathology consistent with CTE can be common among selected brain donors, and the presence of pathological markers does not always map directly onto clinical symptoms. That distinction matters for players, families and clinicians weighing concerns about memory, mood and behavior. Experts also point to ongoing efforts to reduce exposure to repetitive head impacts—through rule changes, helmet standards and limits on contact in practice—as relevant to the question of contemporary risk.
Looking ahead, researchers highlight priorities that follow from the study: reducing sample bias in brain-banking work, improving tools to assess cumulative head-impact exposure in living athletes, and developing diagnostics that could identify neurodegenerative changes before death. Those steps would help clarify how historical findings relate to youth, collegiate and modern professional play and guide evidence-based steps to limit long-term harm from repetitive head impacts and concussion.
