A new study estimates 75% of NFL players who died from 2008 to 2023 had CTE

About three of every four former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, according to an estimate published Wednesday in JAMA Network Open.

The study covered all 2,362 former NFL players who died in that span. Researchers led by Boston University combined brain bank findings from players whose families donated their brains with National Death Index records for players who were not donors. Nearly 94% of the donated brains had CTE, ESPN reported.

Researchers adjusted that figure for selection bias, because families of players who had symptoms are more likely to donate a brain. BU said former players with cognitive symptoms were about five times as likely to be donors, and the researchers used that ratio to adjust the 94% down to an overall estimate of 74.5%.

CTE can be diagnosed only after death. It has turned up in less than 1% of the thousands of brains donated to community brain banks in the United States, Australia, Austria and Brazil, according to BU.

Lead author Julia Gallini, a PhD candidate at the Boston University School of Public Health, said an estimated 75% prevalence among the players "is concerning, and suggests we need to increase efforts to support families, diagnose CTE during life, and treat CTE-related symptoms."

The researchers cautioned that the estimate does not predict how many living former players or active players have CTE, and the study does not address college or youth football. "Many cases may have been early stage at the time of death and possibly symptom free," the paper said, according to ESPN.

The new figure narrows an August study by the same group, which put the share of former players who died between 2016 and 2021 with CTE anywhere from 25% to 98% because it was unclear how representative brain donors were.

The NFL said in a statement that it "continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts." The NFL Players Association said studies like this one "are critical to improving our understanding of football's long-term impacts."

Matt Hasselbeck, an 18-year NFL veteran and an ambassador for the DIAGNOSE CTE study, said in BU's release, "I can't take back the hits I took, but I can sign up for research and do whatever I can to help the scientists so they can find a cure in my lifetime."

BU noted that former players can reach the NFL Life Line, which offers confidential support around the clock, at 800-453-0078.