At least 1-in-4 ex-NFL players who died from 2016 to 2021 had CTE, study finds

At least a quarter of ex-NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, or CTE — a much higher rate than is seen in the general population, a study released Tuesday showed.

CTE is a brain disease linked to repeated blows to the head. Former NFL stars like Junior Seau , Demaryius Thomas and Mike Webster were all found to have the disease, which can only be definitively diagnosed after someone dies by examining their brain tissue. The disease isn't exclusive to football. MLS player Scott Vermillion was also diagnosed with it following his death. NHL players, like Hall of Famer Bobby Hull , were also diagnosed with the disease.

The researchers also found 61.3% of former NFL players who donated their brains and had CTE met the clinical criteria for dementia, and that severe CTE was associated with dementia more frequently.

The study was done by Mass General Brigham, Boston University and the Concussion & CTE Foundation, and was published in The British Medical Journal.

An NFL spokesperson told CBS News the league "continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts."

"The NFL remains committed to ensuring that the NFL community has access to a robust — and expanding — set of resources to enhance their physical and mental wellbeing. We encourage former players to utilize these resources to identify and seek treatment when they are concerned about their health," the spokesperson continued.

Researchers began by identifying all former NFL players who died between 2008 and 2021.

Of the 878 players who died between 2016 and 2021, the highest donation period, some 235 donated their brains, the researchers said. There were 215 (91.4%) donated brains that were diagnosed with CTE.

To take players who didn't donate their brains into account, researchers estimated a range for possible CTE prevalence between 24.5% and 97.7%.

"The true prevalence likely lies somewhere in the middle," they said, which would mean the actual percentage could be much higher than 24.5%.

"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 Daniel Daneshvar, the study's lead author, the chair of physical medicine and rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School.

"These data, alongside my experience treating NFL players with dementia ... indicate that we need to dedicate resources towards developing a cure," he said.

The researchers said future studies should look at athletes who played more recently, and that prevention efforts should "focus on reducing repetitive head impacts that drive CTE risk, not just concussions."