Study Estimates 24.5 Percent of Deceased NFL Players Had CTE

Researchers studying hundreds of brains from deceased NFL players reported Tuesday that at least 24.5 percent had chronic traumatic encephalopathy, a degenerative disease tied to repeated head impacts, based on cases among 878 players who died between 2016 and 2021.

The analysis identified at least 215 cases of CTE among 878 former players who died from 2016 to 2021, while 643 other brains were not examined, meaning the true prevalence could be higher, according to the study described by The New York Times, NPR, and CBC.

Chronic traumatic encephalopathy can only be definitively diagnosed after death, and studies cited by NPR and CBC found that rates of CTE were nearly zero in people without repeated head impacts.

“We were unfortunately both surprised but saddened to see that the minimum rate was so alarmingly high,” said Dr. Daniel Daneshvar, lead author and chair of Physical Medicine and Rehabilitation at Mass General Brigham and an associate professor at Harvard Medical School.

CBC reported the study examined former players who died between 2008 and 2021, including 235 who donated brains, and that more than nine in 10 donated brains showed evidence of CTE.

“They had clinical impairment in their thinking and memory that was so severe they couldn't take care of their own activities of daily living,” Dr. Daneshvar said.

NPR reported that the BMJ paper published Tuesday estimated a minimum around 25% for CTE at death and described the figure as the low end, with the true rate potentially higher.

“The prevalence estimate of 25% is at the "low end," Daneshvar said,” NPR reported.

NPR also said the researchers created a denominator list of 1,712 deceased players from Centers for Disease Control and Prevention death certificates and used it to estimate the share likely affected in the 2016 to 2021 period.

In a statement reported by NPR, an NFL spokesperson said the league “continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts,” and added that the NFL remains committed to expanding resources for physical and mental wellbeing.

NPR reported that the study found a strong link between dementia in life and the most advanced stage of CTE after death, with more than 90% of Stage IV samples also diagnosed with dementia by a clinician based on records and information from loved ones.

“If we're trying to think about how to practically apply this information to living former NFL players who've just left the league, or those who left a while ago and are starting to age, that part deserves further discussion,” said Rachel Grashow, a neuroepidemiologist at the Harvard T. H. Chan School of Public Health, who was not involved in the study.

NPR reported that Grashow said further research is needed and warned that public conversations can create hopelessness that discourages people from seeking treatment for treatable conditions linked to prior head injury symptoms.