One in Four Former NFL Players Had CTE, Major Study Finds

At least one in four former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy, according to a study published August 25, 2026 in the journal JAMA and independently corroborated by Reuters The Guardian.

CTE is a degenerative brain disease that can only be definitively diagnosed after death. It is associated with repeated blows to the head, including concussions, and its symptoms include difficulty with attention and memory, dementia, mood disorders, and headaches.

The study, conducted by Mass General Brigham, Boston University, and the Concussion + CTE Foundation, examined a larger and more recent population than previous research. Of 878 former NFL players who died between 2016 and 2021, 235 donated their brains for study. Of those donated brains, 215 — roughly 91% — were found to have CTE. Because only a fraction of deceased players' brains were donated, the true prevalence across all former players could be lower, but the study's authors frame the one-in-four figure as a floor estimate, not a ceiling.

The lead author, Dr. Daniel Daneshvar, chairs physical medicine and rehabilitation at Mass General Brigham and is an associate professor at Harvard Medical School. He noted that NFL players die from neurodegenerative disease at roughly four times the rate of the general population.

Dementia was common among the brain donors in the study. Researchers urged prevention measures focused on reducing repetitive head impacts across all levels of football — not just the professional ranks.

That last point is critical. Daneshvar said the bulk of head impacts experienced by former NFL players actually occurred at the collegiate, high school, and youth levels, not in the NFL. Nearly 70% of head impacts in a football career happen in practice, he stated, which means the way teams conduct practices matters as much as what happens on game day.

Some rule changes have already targeted that exposure. The NFL's 2011 Collective Bargaining Agreement limited the number of contact practices during the season. The Ivy League went further, banning full-contact tackling during practices in 2016. And in 2016, the U.S. Supreme Court cleared the way for the NFL's settlement of concussion-related lawsuits with thousands of retired players.

This study builds on a longer research record. A 2017 study found CTE in 110 of 111 donated brains from former NFL players. In 2023, Boston University's CTE Center reported diagnosing CTE in 345 of 376 former NFL players whose brains were autopsied — roughly 92%. A 2023 JAMA Neurology study found that most young brain donors with CTE had a mild form of the disease, and a 2024 JAMA Network Open study noted that most diagnosed CTE cases have been in former contact-sport athletes, predominantly elite American football players.

What sets the new study apart is its scope. By looking at all former NFL players who died in a five-year window — not just those whose families chose to donate brains for research — the authors produced a population-level estimate rather than a clinic-based one. The one-in-four figure reflects a broader population than earlier, smaller samples that showed much higher rates among donated brains.

The findings arrive as football continues to grapple with the tension between the sport's appeal and its long-term health costs. The NFL season is weeks away. Millions will watch. This study is a reminder that the consequences of the game can extend far beyond the final whistle.