Study Estimates 1 in 4 Former NFL Players Who Died From 2016 to 2021 Had CTE

A new study estimates that at least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, or CTE, a degenerative brain disease associated with repeated blows to the head.

The study, published Tuesday in the medical journal BMJ, examined deaths among former NFL players and compared those records with brain donations that had been examined for signs of CTE.

Researchers identified 878 former NFL players who died during the six-year period. Of those, 235 had donated their brains for research, and 215 were diagnosed with CTE.

CTE can only be definitively diagnosed after death. The disease is associated with an abnormal buildup of the protein tau in the brain. Symptoms that may be associated with CTE include memory problems, difficulty controlling impulses, depression, anxiety and anger.

Researchers say the new study provides a broader estimate of how common CTE may be among former NFL players because it considered the overall number of player deaths rather than looking only at people whose families chose to donate their brains for research.

A previous study found CTE in 99% of former NFL players whose brains had been donated for research. Researchers noted that study was potentially affected by selection bias because families may have been more likely to donate the brains of players who had experienced concerning symptoms.

The researchers behind the new study say repeated head impacts remain an important concern throughout a football player's career. Lead author Dr. Daniel Daneshvar said many of the head impacts experienced by former NFL players occurred before they reached the professional level, including during college, high school and youth football.

The study also found that dementia was common among the brain donors.

Experts caution, however, that having CTE does not necessarily mean a person experienced specific symptoms while alive. Researchers are still working to better understand the relationship between the amount of tau buildup in the brain, CTE and cognitive or behavioral symptoms.

Dr. Rachel Grashow, a Harvard University researcher who was not involved in the study, said the research is significant because it gives scientists a better denominator for understanding how frequently CTE occurs among former NFL players. She cautioned against assuming that the percentage of players with CTE is the same as the percentage who experienced symptoms.

The NFL said the league continues to work on strategies designed to reduce concussions and head impacts and provide health resources for current and former players.

The study's authors say reducing repetitive head impacts could be an important part of preventing long-term neurological problems. They point to research indicating that a large percentage of head impacts occur during practices rather than games.

Changes have already been made at the professional and collegiate levels to reduce contact during practices. Researchers say expanding those efforts to high school and youth football could further reduce athletes' cumulative exposure to head impacts.

The findings add to ongoing research into the long-term health effects of football and the steps that can be taken to make the sport safer at every level.