Study Finds 74.5% of Deceased NFL Players Had CTE

74.5% of deceased former NFL players had chronic traumatic encephalopathy, according to a study published Wednesday in the Journal of the American Medical Association. The figure represents a narrowing of previous estimates that ranged as high as 98%. The new analysis provides a specific metric for a condition that affects the brain tissue of athletes who suffered repeated head impacts.

The research team examined data on 2,362 deceased former NFL players. Only 396 of those individuals had donated their brains for examination, while 1,966 had not. Among the brains that were examined, 93.5% showed signs of CTE. Researchers adjusted the overall estimate to account for the difference in donation rates between players whose families observed cognitive symptoms and those whose families did not.

Yorghos Tripodis, a professor of biostatistics at Boston University and an author of the paper, explained the need for a more precise figure. "Our group’s earlier study could only say the figure was somewhere between 25% and 98%, and we wanted a more precise answer," Tripodis said. He noted that even under very conservative assumptions regarding donation bias, the estimated rate of CTE does not drop below 60%.

The study also assessed the prevalence of dementia among the cohort. Researchers estimated that 27.2% of the former players had dementia during their lifetime. They stated that this number likely underestimates the true prevalence of the condition. The findings build on prior work published in August, which found that at least one in four former players who died between 2016 and 2021 may have had CTE.

Tripodis highlighted the scale of the issue for the current population. "More than 20 million men alive today in the US have played football, so understanding how many of them have CTE is an important public health question," he told ABC News. The Centers for Disease Control and Prevention describes CTE as a brain disease associated with repeated hits to the head. It involves a buildup of abnormal proteins that damage brain tissue and can cause brain cells to die.

The NFL issued a statement regarding the findings. The league said it "continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts." The statement also referenced the organization's commitment to providing resources to enhance the physical and mental well-being of the NFL community.

The NFL Players Association, the union representing football players, weighed in on the results. The group told ABC News that the data is a "sobering reminder that football carries real risks, and those risks can have lasting consequences for players and their families." The union stated that the findings reinforce its core priority of improving player safety and supporting players throughout their lives, both during and after their careers.

Researchers noted that CTE can only be diagnosed after death, requiring families to donate a loved one's brain for examination. They estimated that families who observed cognitive symptoms in a loved one during life were about five times more likely to donate a brain. The study team adjusted their analysis to account for this potential bias. They cautioned that their findings apply specifically to deceased former NFL players and may not be representative of living players.

In September 2016, NFL Commissioner Roger Goodell announced an initiative called "Play Safe, Play Smart." The organization pledged $100 million to player safety as part of this effort. Goodell described the initiative as a drive to progress in the prevention, diagnosis, and treatment of head injuries while enhancing medical protocols. He said the goal is to further improve the way the game is taught and played by all who love it.

Betsy-Ann Assoumou, MD, MBA, a family medicine resident at Cheshire Medical Center/Dartmouth Health in Keene, New Hampshire, contributed to the medical analysis for ABC News.