Nearly 3 Out of 4 Former NFL Players Who Died May Have Had a Serious Brain Disease, Study Finds

A new study found that about 74.5% of former NFL players who died between 2008 and 2023 likely had a serious brain disease called chronic traumatic encephalopathy, or CTE. That means nearly three out of every four players may have had this condition. Researchers looked at the medical records of more than 2,000 deceased players to reach this conclusion. The study was published in a medical journal called JAMA Network Open.

CTE is a brain disease that gets worse over time. It has been linked to sports where players receive many hard hits to the head, like football. The disease can cause memory loss, confusion, and other serious health problems. Right now, doctors can only confirm CTE after a person has died by studying their brain.

Because CTE can only be found after death, past studies had a big problem called selection bias. This happens when the people studied don't truly represent everyone in the group. For example, players who had memory problems while they were alive were about five times more likely to donate their brains for research than players who felt fine. That made earlier studies show higher rates of CTE than might actually exist.

To get a more accurate number, researchers from Boston University, Mass General Brigham, and the Concussion & CTE Foundation combined data from 2,362 former NFL players who had died. Of those, 396 players had donated their brains for study. The other 1,966 players were tracked using national death records. Almost 94% of the donated brains showed signs of CTE, but researchers adjusted that number down to 74.5% to account for selection bias.

Julia Gallini, the lead author of the study and a PhD student at Boston University, said it is very important to understand how many people might have CTE. She noted that more than 20 million American men alive today have played football at some point in their lives. 'It is crucial to learn how many may have CTE to ensure the medical community is prepared to support families fighting suspected CTE,' Gallini said.

A separate study published two months earlier also looked at CTE in NFL players. That study found that nearly 60% of all NFL brain donors had dementia, which is a condition that causes serious memory loss. Among players with the most severe form of CTE — called Stage IV — more than 90% had dementia. Yorghos Tripodis, a professor at Boston University, said no other known job or environmental exposure has been linked to that level of dementia risk.

Another study published in the British Medical Journal looked at NFL players who died between 2016 and 2021. It estimated that at least one in four of those players had CTE. However, the lead author of that study, Dr. Daniel Daneshvar, said 25% was likely on the low end of the true number. He said the actual rate could be much higher, possibly as high as 97%.

The NFL said in a statement that it works to make football safer by reducing concussions and head impacts. The NFL Players Association, the union that represents players, called studies like this one important for understanding football's long-term impacts. The union also said the findings are a reminder that football carries real risks for players and their families.

CTE is not just a concern for NFL players. Researchers are also worried about players in college football, high school football, and youth leagues. Because the disease can't be found until after death, there isn't much data on younger players yet. CTE has even shown up in other sports — Boston University recently confirmed that Fred Lorenzen, a NASCAR Hall of Fame driver who died at age 89, had Stage 3 CTE and is the first NASCAR driver confirmed to have had the disease.

Scientists are working hard to find ways to diagnose CTE while people are still alive. Gallini said that once doctors can test for CTE in living patients, researchers can begin clinical trials to look for treatments and eventually a cure. She encouraged former players to join studies that are trying to develop those tests. Most importantly, Gallini said the disease can be stopped: 'Repeated head impacts are the only known risk factor, so we need to limit the number of times players are hit in the head.'