At least 1 in 4 former NFL players who died between 2016 and 2021 had CTE, study finds

In a new study from Mass General Brigham, Boston University (BU), and the Concussion & CTE Foundation, researchers found evidence that at least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE) at the time of death, a much higher prevalence compared with the general population.

Researchers also found that 61.3% of NFL donors with CTE met clinical criteria for dementia, with severe CTE more frequently associated with dementia. Results were published in The BMJ.

How the estimates were built

Currently, CTE can only definitively be diagnosed after death through examination of brain tissue. To estimate prevalence, researchers identified all former NFL players from the hard-shell helmet era who died between 2008 and 2021. Between 2016 and 2021, the period with the most donations, 878 former NFL players died. Of those players, 235 donated their brains, and 215 (91.4%) of the donated brains were found to have CTE.

The majority of brains analyzed were donated to the UNITE Brain Bank at the Boston University CTE Center, with additional donations included from the Mount Sinai and University of California San Francisco Alzheimer’s Disease Research Center brain banks. To account for players who did not donate their brains, researchers estimated a range for possible CTE prevalence.

The most conservative estimate assumes that the 215 confirmed cases were the only cases of CTE among all 878 deceased players, resulting in a prevalence of 24.5%, or about one in four former NFL players.

The opposite extreme—that every player who did not donate their brain also had CTE—means that up to 97.7% of players in that study period could have had CTE, although both extremes are highly unlikely. The true prevalence likely lies somewhere in the middle.

“Community brain bank studies have shown that CTE affects less than 1% of the general population. To find that somewhere between 24.5% and 97.7% of NFL players from that time period had this progressive brain disease is a wake-up call for the NFL and scientific communities,” said lead and corresponding author Daniel Daneshvar, M.D., Ph.D., chair of physical medicine and rehabilitation at Mass General Brigham and Earl P. and Ida S. Charlton Associate Professor at Harvard Medical School.

“These data, alongside my experience treating NFL players with dementia in clinic, indicate that we need to dedicate resources toward developing a cure.”