A Boston University-led study estimates that 74.5% of former National Football League (NFL) players who died from 2008 through 2023 had chronic traumatic encephalopathy (CTE) pathology, below the share among evaluated brain donors.
Published Wednesday in JAMA Network Open, the study draws on records for 2,362 deceased former NFL players. Researchers found CTE in 362 of the 387 donated brains that underwent neuropathological evaluation, a rate of 93.5%. That percentage describes the evaluated donors, not all former players represented in the records.
The researchers adjusted the donor result using a model of the likelihood of brain donation. In that model, donation probability was about five times higher for players with clear cognitive symptoms. Because nondonors were not all directly assessed, the researchers inferred symptoms using dementia-related death records and estimated rates of mild cognitive impairment.
After the adjustment for modeled brain-donation selection bias, the estimated prevalence was 74.5%, with a 95% confidence interval of 69.6% to 78.3%. The gap between the donor finding and the adjusted estimate reflects the model’s correction for differences in who was represented among brain donors.
The paper also discusses an earlier study that found CTE in 110 of 111 former NFL brain donors. Its authors cautioned that the donor group was selected and did not represent the wider player population.
Because this analysis covers deaths from 2008 through 2023, it cannot establish CTE prevalence among players who are still living, including current NFL players. CTE can be diagnosed only after death, and the researchers said more work is needed to understand its clinical effects.
Julia Gallini, the study’s lead author and a Boston University Ph.D. candidate, said the findings may help guide support for families and work to identify and treat symptoms linked to CTE, Boston University reported.
