Study: At Least 25% of Former NFL Players Who Died Between 2016 and 2021 Had CTE

CTE can only be diagnosed after death through brain dissection. Previous research has relied on brain donations from families or individuals who often showed symptoms like memory loss or mood swings, making it unclear how representative those samples were. To address this, researchers at Mass General Brigham used the UNITE Brain Bank at Boston University and compiled a complete roster of players who appeared in at least one NFL game since 1949, cross-referenced with death certificates from the CDC.

Of 1,712 players who died between 2008 and 2021, the researchers focused on the 2016–2021 period, when donation rates were highest. The minimum prevalence was 25%, but the authors said the actual figure is likely higher. They pointed to additional CTE diagnoses made outside the brain bank sample, 215 non-donor death certificates listing neurodegenerative diseases, and cases where the brain was not evaluated. At the upper extreme, if all but 20 brains cleared of CTE had the disease, prevalence would be about 97%. Lead author Dr. Daniel Daneshvar said the true rate is "somewhere in the middle."

The study also examined dementia. More than 90% of brains with Stage IV CTE had been diagnosed with dementia in life, but the connection was less clear at lower stages. About 40% of brains without CTE also had dementia diagnoses.

In response, an NFL spokesperson told NPR the league "continuously strives to make the game of football safer," including strategies to reduce concussions and head impacts, and remains committed to providing resources for former players’ physical and mental wellbeing.

Rachel Grashow, a neuroepidemiologist at Harvard T.H. Chan School of Public Health not involved in the study, said further research is needed to apply these findings to living former NFL players, thousands of whom are still alive.