Boston researchers estimate three-quarters of late NFL players had brain disease signs

Ninety-three point five percent of donated brains from deceased former National Football League players showed evidence of chronic traumatic encephalopathy, according to a new study released on Wednesday. The research, published in Jama Network Open, estimates that approximately 75% of all ex-NFL players who died between 2008 and 2023 had signs of the degenerative brain disease.

The study was conducted by a team based in Boston and analyzed records for 2,362 former players who spent an average of five years in the league. Close to 400 of these individuals had their brains donated for examination. The authors stated that this is the first effort to estimate CTE prevalence among all deceased players in that timeframe, rather than limiting the scope to those who donated brain tissue.

The researchers noted a stark difference between the player cohort and the general public. Fewer than 1% of brain samples in community-based brain banks contain evidence of CTE. Physical markers of the condition include brain atrophy, which is a loss of brain tissue, and accumulations of tau protein, a substance also associated with Alzheimer's disease.

The study outlined limitations in interpreting the findings. The presence of CTE-related changes does not automatically result in dementia or cognitive decline, and some individuals never develop noticeable symptoms. The researchers estimated that about 27% of the former players in the analysis had dementia. The condition can also impact areas of the brain controlling emotion and behavior, potentially causing depression, memory issues, and severe mood shifts.

Yorghos Tripodis, the senior author of the study, acknowledged in a statement issued by Mass General Brigham that the findings might cause concern for living players and their families. He said researchers are standing by to provide support and expressed hope for those living with CTE. Tripodis added that discoveries from the brain bank have brought researchers significantly closer to diagnosing the condition during life, making the development of effective treatments the primary next step.

These results follow a report released in August that found at least one in four former NFL players who died between 2016 and 2021 had CTE. Following that earlier report, the NFL stated it continuously strives to make the game safer by implementing strategies to reduce concussions and head impacts. Several high-profile former players who died by suicide, including Junior Seau, Dave Duerson, and Aaron Hernandez, were found to have had CTE during posthumous brain examinations.