CTE Prevalence: 75% of Deceased NFL Players Affected

Scientists at Boston University, Mass General Brigham, and the Concussion & CTE Foundation released findings on Wednesday, October 28, estimating that 75% of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy.

The study, published in JAMA Network Open, analyzed 2,362 cases. It combined data on 396 players who donated their brains for research with National Death Index records for 1,966 players who did not. The researchers described the work as the first comprehensive scientific effort to measure how widespread the neurodegenerative disease was among deceased former professionals.

Nearly 94% of the donated brains showed evidence of CTE. However, the authors noted that donors differed from non-donors. Players who donated their brains were more likely to be white, die at a younger age, and spend more years playing in the NFL. These disparities address previous criticisms that brain donation studies suffer from selection bias by disproportionately including players who showed symptoms during their lives.

The authors stated that their analysis accounted for these demographic and career differences. Even after adjusting for the fact that donors were more likely to be symptomatic, the estimated prevalence remained high.

Lead author Julia Gallini called the nearly 75% estimate concerning. She urged greater efforts to support families, develop methods for diagnosing the disease while patients are alive, and treat associated symptoms. The team noted that symptoms often do not appear in the earliest stages of CTE. This suggests many players may have died without showing obvious signs of the condition.

The estimate applies only to deceased NFL players. It does not predict how common CTE is among living professionals or among college and youth football players. CTE can currently be diagnosed only after death, though research into in-life testing continues. The study also pointed to gaps in knowledge regarding high school and college athletes, partly due to a shortage of data on deceased players who did not donate their brains.