A new study led by Boston University researchers estimates that nearly 75% of all NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) neuropathology, which can only be diagnosed after death.
“Providing a precise estimate for the prevalence of CTE among deceased NFL players helps define the scale of the problem and informs priorities for the potential current and future medical needs of this community,” said Julia Gallini, lead author and a PhD candidate at Boston University School of Public Health.
The new findings build on an August 2026 study from the same research group that estimated that between 25% and 98% of former NFL players who died between 2016 and 2021 had CTE. The wide range reflected uncertainty about how representative brain donors were of the overall NFL population. Brain donors are more likely to have symptoms believed to be related to CTE, a concept known as selection bias.
For new study, published in JAMA Network Open, researchers analyzed this selection bias to estimate the prevalence of CTE in players they didn’t directly study. This estimate was made possible by understanding the differences between NFL players whose brains were donated and NFL players whose brains were not donated. Among the 387 deceased NFL players that were studied, 362 (94%) had some degree of CTE neuropathology. Researchers then studied available records of death certificates from the National Death Index for all 2,362 NFL players from this era, which included data on how many died of neurodegenerative disease and had dementia.
Researchers also analyzed other factors associated with brain donation, including cognitive symptoms, age at death, position and years played in the NFL. From this analysis, they estimated that former players with cognitive symptoms were about five times more likely to have their brains donated by their family than those without such symptoms.
The researchers used this estimated selection ratio to adjust the 94% prevalence of CTE observed among brain donors to an overall estimate of 74.5%. This is the first estimate of CTE neuropathology prevalence among all 2,362 deceased former NFL players, including those who did not have their brains donated and were not measured directly.
Data from Boston University