About 74.5% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, or CTE, according to a new estimate from researchers at Boston University, Mass General Brigham and the Concussion & CTE Foundation. The study, published Oct. 28 in JAMA Network Open, drew on records for 2,362 deceased former players, ABC News reported on the new estimate.

The figure is a statistical estimate, not a count of diagnoses. CTE, a brain disease linked to repeated hits to the head, can be confirmed only by examining the brain after death, and most players' brains were never studied. The researchers combined findings from donated brains with death records to estimate the likely rate across all players who died in that period.

For families of former players, the number turns an abstract risk into a household question. Many spouses, adult children, and caregivers already manage memory loss, mood changes or dementia in a loved one, and the estimate suggests those experiences are common rather than rare.

Correcting for Families Who Donate

The study's central challenge was selection bias. Families who notice cognitive or behavioral symptoms in a loved one are more likely to donate the brain, which can make CTE look more common among donors than among all players.

Among donated brains, 362 of 387 had some form of CTE, or about 94%, CBS News reported. The researchers estimated that former players with cognitive symptoms were about five times more likely to have their brains donated, and they used that ratio to adjust the rate to 74.5% for all deceased players.

Even under very conservative assumptions, the estimate "does not go below 60%," said co-author Yorghos Tripodis, a professor of biostatistics at Boston University. The researchers also estimated that 27.2% of the former players had dementia during their lifetime, a figure they said likely understates the true rate.

The work narrows a much wider range from an August study in The BMJ by many of the same researchers. That study, based only on brain donors, estimated that at least 24.5% and as many as 97.7% of former players who died between 2016 and 2021 had CTE.

What the Evidence Can and Cannot Show

The study is observational and relies on brain examinations, death records, and statistical modeling, not on brain exams of every player. It does not show how many hits or seasons cause CTE in any individual, and it does not estimate how many living or active players have the disease.

The result depends on the assumption about how much more likely symptomatic families are to donate. If that ratio is off, the estimate shifts, which is why the researchers reported a conservative floor.

The findings stand in sharp contrast with the general population. Lead author Julia Gallini, a doctoral candidate at the Boston University School of Public Health, noted that CTE is "consistently found in less than 1% of donors to community brain banks" and said the estimated 75% prevalence among deceased NFL players is concerning, Boston 25 News reported. She said more work is needed to support families, diagnose CTE during life and treat related symptoms.

Dr. Ann McKee, director of the Boston University CTE Center, said the estimate shows that "football played at the professional level is a real risk for this disease." She also called CTE "a preventable disease," according to WBUR. Because the estimate comes from the research group behind the brain bank, confirmation by independent teams will matter.

The NFL said it "continuously strives to make the game of football safer," pointing to rule changes, concussion-reduction efforts, and equipment such as Guardian Caps. The NFL Players Association said studies like this one are critical to understanding football's long-term health effects.

What Former Players and Families Can Do

The estimate applies to deceased professional players, not to people who played only high school or college football. Still, it matters to the many men who played the game. "More than 20 million men alive today in the US have played football," Tripodis said.

CTE cannot yet be diagnosed in living people, but symptoms researchers associate with it, including memory loss, confusion, depression, mood swings and impulsive behavior, can be evaluated and often treated. Former players or family members who notice those changes can ask a primary care doctor about a referral to a neurologist or memory clinic, since other causes of similar symptoms, such as sleep apnea, depression, or medication effects, are treatable.

Anyone with thoughts of suicide or self-harm can call or text 988, the 988 Suicide and Crisis Lifeline. Sudden confusion, a severe headache, or weakness on one side of the body needs emergency care.

McKee said the risk can be lowered by raising the age at which children start playing tackle football and by reducing head hits overall, whether or not they cause concussions. Parents of young athletes can ask coaches about limits on full-contact practice and what the team's concussion protocol requires before a child returns to play. Former NFL players can also find support through player resources such as the NFL Lifeline and the NFL Players Association's programs.

Researchers are working toward tests that could detect CTE in living people, a step that would change how families plan care. For now, CTE appears common among former NFL players who have died, while the exact rate remains an estimate with real uncertainty.

Key Questions Answered

What did the study estimate? That about 74.5% of former NFL players who died between 2008 and 2023 had CTE.

Is this a count of diagnosed cases? No. It is a statistical estimate. Among donated brains, 362 of 387 had CTE.

How did researchers adjust for donation bias? They estimated that players with cognitive symptoms were about five times more likely to be brain donors and adjusted the rate accordingly.

Can CTE be diagnosed in living people? Not yet. It can be confirmed only by examining the brain after death.

Does this apply to youth or college players? No. The estimate covers deceased professional players only.

What should families do if they notice symptoms? Ask a doctor about evaluation by a neurologist or memory clinic, since many symptoms can be treated.

Published by Medicaldaily.com