A new analysis of brain tissue from former National Football League players found that at least 25% of those who died between 2016 and 2021 had a degenerative brain disease, the study's authors said.
The research, which reviewed cases from that five-year period, concluded that a minimum of one in four of the examined former players showed pathological evidence of a progressive brain condition. The investigators cautioned that this figure should be regarded as a lower bound and that the actual prevalence among former players could be considerably greater.
Researchers pointed to limitations in the available data and sampling methods that make a precise estimate difficult. They warned that factors such as how brains are selected for study and the size of the sample can affect measured rates, and said further work is needed to establish more representative prevalence estimates.
The findings add to an ongoing conversation about long-term brain health among participants in contact sports and the potential consequences of repeated head trauma. The study’s authors called for additional, larger-scale research to clarify the risks and to guide medical care, prevention efforts and policy discussions involving athletes, leagues, and medical professionals.
While the report does not by itself change clinical guidance, it underscores continuing scientific and public concern about degenerative brain disease in former sports professionals and the need for more comprehensive data to inform safety measures and support for affected players and families.