Researchers find alarming rates of CTE in former football players

In a new study from Mass General Brigham, Boston University (BU), and the Concussion & CTE Foundation, researchers found evidence that at least 1-in-4 former NFL players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE) at the time of their death, a much higher prevalence compared to the general population. Researchers also found that 61.3% of NFL donors with CTE met clinical criteria for dementia, with severe CTE more frequently associated with dementia. Results were published today in The BMJ.

Currently, CTE can only definitively be diagnosed after death through examination of brain tissue. To estimate prevalence, researchers identified all former NFL players from the hard-shell helmet era who died between 2008 and 2021. Between 2016 and 2021, the highest donation period, 878 former NFL players died. Of those players, 235 donated their brains, and 215 (91.4%) of the donated brains were found to have CTE.

The majority of brains analyzed were donated to the UNITE Brain Bank at the Boston University CTE Center, with additional donations included from the Mount Sinai and University of California San Francisco Alzheimer's Disease Research Center brain banks. To account for players who did not donate their brains, researchers estimated a range for possible CTE prevalence. The most conservative estimate assumes that the 215 confirmed cases were the only cases of CTE among all 878 deceased players, resulting in a prevalence of 24.5%, or about 1-in-4 former NFL players.

The opposite extreme-that every player who did not donate their brain also had CTE-means that up to 97.7% of players in that study period could have had CTE, although both extremes are highly unlikely. The true prevalence likely lies somewhere in the middle.

Community brain bank studies have shown that CTE affects less than 1% of the general population. To find that somewhere between 24.5% and 97.7% of NFL players from that time period had this progressive brain disease is a wake-up call for the NFL and scientific communities. These data, alongside my experience treating NFL players with dementia in clinic, indicate that we need to dedicate resources towards developing a cure."

Daniel Daneshvar, MD, PhD, lead and corresponding author, Chair of Physical Medicine and Rehabilitation at Mass General Brigham and Earl P. and Ida S. Charlton Associate Professor at Harvard Medical School

The study also found that dementia was common among brain donors, and 95.5% of donors with dementia had CTE pathology. The most severe form of the disease, Stage IV CTE, was strongly associated with dementia and with greater impairment in cognition and daily functioning.

"We recognize that these findings will be concerning for NFL players and their families, and we want them to know that help is available," said senior author Jesse Mez, MD, MS, associate professor of neurology at the BU Chobanian & Avedisian School of Medicine and co-director of clinical research at the BU CTE Center. "We have treatments for many symptoms believed to be associated with CTE, and in our clinic we find that symptoms can improve with proper medical care."

Researchers note that future studies should examine athletes who played more recently, and that prevention efforts should focus on reducing repetitive head impacts that drive CTE risk, not just concussions.

Former NFL players concerned about their brain health or the risk of neurodegenerative disease should consider being evaluated by a clinician who specializes in these conditions. It's important to remember that many health issues can mimic neurodegenerative disease, and many are treatable. While it's not always possible to eliminate long-term risk, identifying and addressing modifiable risk factors can support brain health and improve quality of life. If you're seeking guidance, help finding a specialist, or support in managing your health, resources are available through The Trust Powered by the NFL Players Association (NFLPA), the NFLPA's Professional Athletes Foundation, and the Concussion & CTE Foundation HelpLine.