Study finds 75% of deceased ex-NFL players likely had brain disease

Scientists from Boston University, Mass General Brigham, and the Concussion & CTE Foundation estimate that three in four former NFL players who died between 2008 and 2023 suffered from chronic traumatic encephalopathy. The study, published in JAMA Network Open on Wednesday, represents the first comprehensive scientific assessment of CTE prevalence among deceased former professionals in the league.

The research team examined 2,362 cases. This total included 396 players who donated their brains for study and 1,966 players identified through National Death Index records who did not donate. The data showed that 94% of the donated brains contained evidence of the neurodegenerative disease.

Researchers noted that players who donated brains differed from those who did not. Donors were more likely to be white, died at younger ages, and played in the NFL for longer periods. These differences address previous criticisms of selection bias in earlier studies, which often relied heavily on brains from players who showed symptoms during their lives.

Despite these demographic differences, the authors stated their analysis accounted for donation status while still indicating a high rate of CTE. They clarified that the 75% estimate applies only to deceased players and cannot predict rates among living former professionals or players in college and youth football.

Julia Gallini, the lead author, described the nearly 75% figure as concerning. She urged for increased efforts to support families, develop tests for diagnosis during a player’s lifetime, and treat symptoms associated with the condition. CTE is currently diagnosable only after death, though research into antemortem testing continues.

The study also pointed out gaps in knowledge regarding high school and college football. A lack of data on deceased players who did not donate brains makes it difficult to research the long-term effects of youth tackle football. CTE severity is categorized into four stages, and symptoms often do not appear until the disease progresses beyond the earliest stages.

The NFL stated it works continuously to improve safety through measures aimed at reducing concussions and head impacts. The league encouraged former players with health concerns to seek evaluation and treatment. The NFL Players Association said studies of this nature are critical for understanding the long-term physical effects of playing football.

An earlier paper from August involving some of the same researchers had estimated that one in four former NFL players who died between 2016 and 2021 had the disease. The new study expands that timeframe to include deaths from 2008 through 2023, providing a larger sample size for the prevalence estimate.