Study Finds Brain Disease CTE in 75% of Deceased Former NFL Players

A new study published in Jama Network Open estimates that roughly 75% of former NFL players who died between 2008 and 2023 had evidence of chronic traumatic encephalopathy, a degenerative brain disease. The research was conducted by a Boston-based team and is described as the first attempt to estimate CTE prevalence across all deceased former players from that period, rather than only those whose brains were donated for study.

The analysis drew on records of 2,362 former players who had spent an average of five years in the league. Among the smaller group of nearly 400 players whose brains were actually examined, 93.5% showed signs of the disease.

By comparison, researchers noted that fewer than 1% of brain samples from the general population, collected through community-based brain banks, show evidence of CTE. The disease is associated with brain tissue loss and buildup of tau protein, a change also linked to Alzheimer's disease.

The study also estimated that about 27% of the former players had dementia. CTE has been tied to symptoms such as depression, memory issues and severe mood swings, though researchers noted that evidence of the disease does not guarantee a person will develop dementia or cognitive decline.

The study's senior author said the findings might worry current players and their families, but stressed that support systems exist and that progress is being made toward diagnosing CTE in living patients, which could eventually lead to treatments.

The research follows an earlier study from August that found at least one in four former NFL players who died between 2016 and 2021 had CTE. In response to that earlier study, the NFL said it continues working to make the sport safer, including efforts to reduce concussions and head impacts. Several prominent former players who died by suicide, including Junior Seau, Dave Duerson and Aaron Hernandez, were later found to have had CTE.