Study Finds CTE in 74.5 Percent of Deceased Ex-NFL Players

A new study estimates that 74.5 percent of former National Football League players who died between January 2008 and December 2023 had chronic traumatic encephalopathy, or CTE.

Researchers published the findings in JAMA Network Open on October 28, 2026. The team examined data from 2,362 deceased former players. Only 396 of those men had donated their brains for examination.

The study found CTE in 362 of the 387 donors whose status was determined, a rate of 93.5 percent. Nine donors had undetermined status and were excluded from that specific calculation. However, the authors noted that donated brains do not always represent the entire population of former players.

Families may be more likely to donate a brain if a loved one showed memory issues or other cognitive symptoms before death. This selection bias can make donor-based estimates appear higher than the actual rate across all players. To correct for this, the researchers used National Death Index records and statistical modeling. This adjustment lowered the estimated prevalence to 74.5 percent.

A more conservative analysis within the study placed the estimate at 63.7 percent. The work involved researchers from Boston University, Mass General Brigham, and the Concussion & CTE Foundation. The study also estimated that 27.2 percent of the deceased players had experienced dementia during life. This figure includes dementia from any cause, not just CTE.

The estimates apply only to deceased former NFL players. They do not account for living players, college athletes, or youth players. The data also does not show how many people with CTE had disabling symptoms, as some early-stage cases may have been symptom-free. Because most brains were not examined, the overall estimate relies on assumptions about symptoms and donation decisions. The authors acknowledged that unmeasured factors could still influence the results.

The researchers concluded that donation bias raises the donor-based estimates but is unlikely to fully explain the high burden of CTE among deceased former NFL players.