CTE Study Finds At Least 25 Percent Of Former NFL Players Who Died Had The Brain Disease

A landmark study published Tuesday in The BMJ, one of the world's most prominent peer-reviewed medical journals, has produced the first scientifically rigorous estimate of how common chronic traumatic encephalopathy is among retired NFL players, and the number is 25 percent at minimum.

Researchers at Mass General Brigham, led by Dr. Daniel Daneshvar, began by identifying every player who had appeared in at least one NFL game since 1949.

They cross-referenced demographic data against death certificates from the Centers for Disease Control and Prevention, producing a denominator list of 1,712 former NFL players who died between 2016 and 2021, the window in which voluntary brain donation rates were highest.

They then compared that list against the brains donated to CTE research during the same period and ran the math.

The result: a minimum of 25 percent of the former NFL players who died in that window had CTE confirmed on examination.

"We've known that this disease process can be caused by, in part, repeated traumatic brain injury," Daneshvar said. "But we didn't know how common it was."

The 25 percent figure is, by the researchers' own description, a floor rather than a ceiling.

It reflects only confirmed CTE cases in brains that were donated, not every former player who died during the period had their brain studied, meaning the actual prevalence could be considerably higher.

The mean age of death in the study cohort was approximately 66 years old, meaning most of the players whose brains were examined played their careers before 2005, when CTE was first diagnosed in a former NFL player.

The NFL has made meaningful rule changes in the intervening decades, banning helmet-to-helmet hits, eliminating traditional kickoffs, funding helmet safety research, and researchers caution the current prevalence among players who entered the game more recently may be lower.

CTE is a degenerative brain disease caused by repeated head trauma. It can only be diagnosed after death through brain tissue examination. Symptoms in living patients, which cannot be attributed to CTE without the post-mortem diagnosis, include memory loss, cognitive decline, depression, aggression and impulse control problems.

There is no cure, no treatment and no way to detect it in a living person. Billy Ray Smith Jr., the Chargers linebacker who died last month at 64 from dementia, was among the most recent former players whose family attributed his decline to CTE.

OJ Brigance, the Ravens Super Bowl champion who died from ALS after a 19-year battle, had separately raised awareness of the neurological risks former players face.

The NFL said in a statement that it has committed more than $400 million to independent medical research on player health since 2016 and that its ongoing efforts include improving protective equipment, updating rules to reduce high-risk plays and expanding longitudinal health studies of active and retired players.