Study Finds CTE in Roughly Three Out of Four Former NFL Players Who Died Between 2008 and 2023

A new study led by researchers at Boston University estimates that nearly 75% of NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, known as CTE.

CTE is a degenerative brain disease linked to repeated blows to the head. It can only be definitively diagnosed after death. The condition has been found in football players, other athletes, first responders and military members.

The research appeared in JAMA Network Open. Lead author Julia Gallini said in a statement that CTE is rarely seen in the general population but is far more common among deceased NFL players. "With CTE consistently found in less than 1% of donors to community brain banks, an estimated 75% prevalence among NFL players who died over a 16-year period is concerning, and suggests we need to increase efforts to support families, diagnose CTE during life, and treat CTE-related symptoms," Gallini said.

The findings build on an earlier study released in August, which estimated that between 25% and 98% of former NFL players who died from 2016 to 2021 had CTE. Boston University said that wide range reflected uncertainty over how representative brain donors were of the full NFL population. Donors are more likely to have symptoms believed to be related to CTE, a problem known as selection bias.

In the new analysis, 362 of 387 deceased former players were found to have some form of CTE. To account for selection bias, the researchers factored in that former NFL players with cognitive symptoms were five times more likely to have their brains donated to science. Using that estimated selection ratio, they adjusted the 94% prevalence observed among brain donors to an overall estimate of 74.5%.

The authors noted that the study covered only players who have died. It does not predict how many living former players, or those currently active, might have CTE.

Former NFL quarterback Matt Hasselbeck, an ambassador for the study, said the data should guide efforts to improve safety. "It's hard to learn what the guys who built the game have suffered through," he said. "We have to learn from this data to make the game safer, because we can't accept these numbers for the next generation of players."

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 league pointed to improved equipment and rule changes designed to protect players. It added that it remains committed to giving the NFL community access to a robust and expanding set of resources for physical and mental wellbeing, and encouraged former players to use them if they are concerned about their health.

The NFL Players Association called the study one of many that are "critical" to understanding the long-term health effects of football. The union said it remains committed to supporting scientific research, investing in resources for players' physical and mental well-being, and expanding access to care during and after their playing careers.