The JAMA Network Open research covers players who died between 2008 and 2023 and adjusts for selection bias in brain donation.
Researchers at Boston University, Mass General Brigham, and the Concussion & CTE Foundation published a new study in JAMA Network Open estimating that approximately 74.5 percent of former NFL players who died between 2008 and 2023 had CTE, the neurodegenerative brain disease linked to repeated head impacts in contact sports.
The figure marks a jump from an earlier estimate. In August, a study in the British Medical Journal, using many of the same researchers, put the number at roughly 24.5 percent of former NFL players who died between 2016 and 2021. That earlier study prompted the NFL Players Association to call it "a sobering reminder that football carries real risks."
The new, higher estimate comes after researchers adjusted for selection bias in brain donation, since families who suspect a loved one had CTE are more likely to donate the brain for study in the first place. Most of what is known about CTE in NFL players still comes from donated brain tissue rather than from a representative sample of the full player population, which has made it difficult to pin down exactly how common the disease is across the league's history.