Study finds CTE in at least 24.5% of deceased NFL players from 2016 to 2021

Postmortem findings across six years

A study published on Tuesday in the British Medical Journal reveals that at least 24.5% of former National Football League players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE). Researchers from Mass General Brigham, Harvard Medical School, Boston University, and the Concussion & CTE Foundation analyzed 878 deceased former players over the six-year period. Families of 235 players donated their brains for neuropathological examination, leaving 643 brains unexamined. Among the 235 examined brains, pathologists diagnosed CTE in 215 cases. Researchers calculated that the true prevalence among all deceased players in the period falls between a conservative minimum of 24.5% and a maximum of 97.7%.

Cumulative impacts across amateur and youth football

CTE is a progressive degenerative brain disease that can only be definitively diagnosed postmortem through direct tissue examination. Medical researchers associate the condition with repeated blows to the head and concussions, causing symptoms such as memory loss, depression, cognitive impairment, mood swings, headaches, and dementia. Lead author Daniel Daneshvar, associate professor at Harvard Medical School and chair of physical medicine and rehabilitation at Mass General Brigham, explained that the risk stems from cumulative career hits. Daneshvar pointed out that most head trauma occurs before athletes ever enter the professional ranks.

The bulk of the head impacts that these former NFL players experienced didn't occur at the NFL level. They occurred at the collegiate level... and at the high school level and in many cases the youth level. And all of those cumulative hits to the head added up to result in an increased risk.

Active roster implications and league response

Applying the study's conservative rate to the modern league indicates that at least 400 of the 1,696 players on active 32-team rosters could eventually develop CTE, excluding practice squads and injured reserves. Daneshvar noted that former players face approximately four times the mortality rate from neurodegenerative disease compared to the general population. The disease has also been documented in boxing, hockey, rugby, soccer, wrestling, bobsledding, and military personnel exposed to blasts. In response to the published findings, league officials stated that they remain committed to providing medical resources to retired players and encouraged former athletes to seek clinical treatment.

The NFL continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts.

Policy changes and legal history

The findings follow years of scrutiny regarding head injuries and contact rules across American football. In 2011, the NFL and its players association agreed to limit full-contact practices during the regular season to reduce total impacts. The Ivy League banned tackling during practices in 2016, the same year the US Supreme Court cleared the league's concussion settlement with thousands of retired athletes. Notable posthumous diagnoses have included Pro Football Hall of Fame members Junior Seau, Ken Stabler, and Frank Gifford, as well as Vincent Jackson and Kevin Ellison. Other high-profile cases connected to CTE have involved violent crimes, including former players Aaron Hernandez, Phillip Adams, and Shane Tamura. Researchers have urged youth, high school, and college leagues to adopt practice limits similar to the NFL's cap of fewer than one full-contact practice per week.