Researchers from Boston University, Mass General Brigham, and the Concussion & CTE Foundation released a study on Wednesday, October 28, 2026, estimating that 74.5% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE). The degenerative brain disease is linked to repetitive head impacts and can currently only be definitively diagnosed after death. The research, published in JAMA Network Open, used a statistical model to adjust for selection bias, as families of players with cognitive symptoms are more likely to donate brains for research.
The study analyzed 387 brains donated by former players, representing a portion of the 2,362 NFL players who died during the study period. While 94% of the donated brains were found to have CTE, researchers adjusted this figure to 74.5% to account for the fact that donors with cognitive symptoms were estimated to be five times more likely to participate in brain banking than those without symptoms. A "conservative lower-bound analysis" in the study estimated the prevalence at 63.7%.
Medical experts noted the study's limitations, emphasizing that these findings describe deceased players and do not necessarily reflect the health of current or living athletes. Dr. Kristen Dams-O'Connor of Mount Sinai pointed out that many players in the study ended their careers decades ago, before the NFL implemented modern safety measures like Guardian Caps and updated concussion protocols. The NFL stated it "continuously strives to make the game of football safer" through strategies intended to reduce head impacts.
The findings may influence how current and former professional athletes monitor their neurological health. Dr. Jay Alberts of the Cleveland Clinic Concussion Center noted that detecting early warning signs through "instrumental activities of daily living"—such as changes in driving ability or managing finances—could help identify changes five to seven years before a diagnosis, similar to Alzheimer's or Parkinson's. This data may also impact the development of biomarkers, which researchers hope will eventually allow for CTE diagnosis and treatment during a patient's life.
The NFL continues to implement rule changes and equipment regulations aimed at mitigating repetitive brain injury. Former players seeking guidance are encouraged to utilize resources such as The Trust, the Professional Athletes Foundation, and the NFL Life Line. Researchers stated that further long-term studies are needed to determine if recent safety changes will result in lower CTE prevalence for future generations of players.