Landmark Study Finds at Least 1 in 4 Former NFL Players Died With CTE

A Disease Hidden in Plain Sight

The largest study ever conducted on deceased NFL players' brains has confirmed what many researchers feared — and the true prevalence of the disease is likely even higher than the headline numbers suggest. Published on Tuesday, August 25, in the British Medical Journal, the findings paint a sobering picture of what a career in professional football may cost players long after the final whistle.

At minimum, nearly a quarter of all former NFL players who died from 2016 to 2021 had confirmed chronic traumatic encephalopathy (CTE) — a neurodegenerative disease linked to repeated head impacts — at the time of death. The study was conducted by Mass General Brigham, Boston University, and the Concussion & CTE Foundation. It is the most comprehensive population-level estimate of CTE prevalence ever attempted.

How the Research Was Done

Researchers examined brain samples from some of the 878 players who had appeared in at least one NFL game, in any year, and died during that six-year period. They referenced demographic data and obtained death certificates for all deceased players from the Centers for Disease Control and Prevention to create a denominator list of 1,712 players who died in the same time period. That methodological rigor is what makes this study stand apart from earlier research.

Of the 878 players who died from 2016 to 2021, 215 — or 24.5% — were diagnosed with CTE, which researchers called a conservative estimate. They say the actual rate could be as high as 97.7%, depending on how many players whose brains were not examined after death also had the disease. The true prevalence likely lies somewhere in the middle, researchers said. CTE has been linked to repeated head injuries and can only be diagnosed after death, which makes pinning down an exact figure nearly impossible while players are still alive.

Players whose brains showed the most advanced CTE (stage IV) were also more likely to have symptoms typical of dementia before death, such as memory loss and impaired cognitive function. Researchers found that 104 brain donors had stage IV CTE, while 202 had clinically diagnosed dementia. A total of 63 had neurodegenerative disease listed as their primary cause of death.

What This Means Beyond the NFL

Among the general population, CTE affects less than 1 percent of people. That makes the NFL figures staggering by comparison. According to the study's results, in a 50-person professional football team, at least 12 players could develop CTE. Lead author Dr. Daniel Daneshvar was direct about what the numbers demand: "To see that, at a minimum, 25 percent of NFL players have this pathology in their brain when they die, that means that we need to move towards how to treat this disease and how to cure it for these individuals."

Daneshvar also stressed that although the study focused on former professional football players, these athletes didn't acquire their head impact exposure only at the professional level — they were exposed to head impacts at the collegiate level, at the high school level, and in many cases, the youth level. That reality broadens the public health implications well beyond the NFL.

Context, Caveats, and What Comes Next

Among the former players whose brains were donated, the mean age at death was around 66 years old, meaning most of their professional football careers took place before 2005, when CTE was first diagnosed in a former NFL player. As scientific understanding of the relationship between repeated head trauma and neurodegenerative conditions has grown, the league has taken steps to improve player safety, such as banning dangerous plays like traditional kickoffs and helmet-to-helmet tackles, and funding research into safer equipment. Some experts caution that today's players may face a different risk profile as a result.

The next challenge, researchers say, is to measure the long-term neurological consequences of repetitive head impacts well enough to inform athletes, clinicians, sporting organizations, and policymakers — including identifying CTE during life. Above all, existing and emerging evidence must be regularly shared with past, present, and prospective NFL players, ensuring that consent to play is obtained with full knowledge of the potential risks involved. With millions of young Americans playing football at every level, that conversation has never been more urgent.