At Least 24.5% of Former NFL Players May Develop CTE, Study Finds

At least one in four NFL players could develop chronic traumatic encephalopathy (CTE), a progressive brain disease linked to repeated head impacts, according to new research. The study, led by Dr. Daniel Daneshvar and involving researchers from Boston University and other institutions, examined the brains of 235 former NFL players who died between 2016 and 2021 and found CTE in 215 cases, representing 24.5% of the total 878 players who died during this period. However, since only 235 out of 878 brains were examined, the actual prevalence could be higher.

CTE can cause memory loss, confusion, mood changes, and other cognitive and behavioral issues. It is definitively diagnosed only after death and is extremely rare without repeated head trauma. The disease has been found in athletes across various contact sports, including boxing, hockey, and soccer, as well as in some military personnel exposed to blasts.

Applying the study’s findings to the current NFL roster suggests at least 400 of the 1,696 active players could eventually develop CTE, not accounting for practice squad members or those injured. The NFL has historically downplayed the risks of head injuries, though it has implemented safety measures like banning dangerous hits and improving helmet technology. A 2025 Harvard study emphasized that safety equipment alone cannot eliminate the risk, advocating for stricter concussion protocols and reduced contact in practices. Dr. Daneshvar suggests preventing cumulative head impacts, potentially by keeping children out of tackle football and eliminating contact in practices.

The NFL responded by reaffirming its commitment to safety and player wellbeing, while the NFL Players Association called the research a “call to action” for the entire football ecosystem to improve safety and support players.

Cases like those of Pro Football Hall of Famers Junior Seau, Ken Stabler, and Frank Gifford, who were diagnosed with CTE posthumously, and tragic incidents involving Aaron Hernandez and Phillip Adams, highlight the severe consequences of the disease. A recent case in July 2025 involved Shane Tamura, a non-NFL football player who killed four people before being found to have CTE, further underscoring the disease’s impact.