Boston University finds CTE lesions in 75% of deceased NFL players

A research team led by Boston University evaluated the prevalence of chronic traumatic encephalopathy (CTE) among 2,362 former National Football League (NFL) players who died between 2008 and 2023, gigazine.net reported gigazine.netgigazine.netgigazine.netOpen source ↗. Using statistical modeling designed to adjust for brain donation bias, the investigators estimated that approximately 74.5%—around 1,760 individuals—had developed neuropathological signs of CTE.

CTE is a progressive neurodegenerative disease associated with repeated impacts to the head, which can lead to memory deficits, cognitive decline, and alterations in mood or behavior. According to neurosurgeon Julian Bailes of Endeavor Health, mechanical forces cause the brain to shift within intracranial fluid and strike the cranial vault, prompting the accumulation of pathological tau protein in functional regions. Conclusive diagnosis currently requires post-mortem examination of brain tissue.

Correcting donation bias

Earlier investigations into post-mortem cohorts observed CTE signs in up to 99% of donated brains, but those samples carried significant ascertainment bias because symptomatic athletes are more likely to undergo organ donation. To establish a more generalizable estimate, Yorghos Tripodis and colleagues combined direct tissue assessments with demographic and epidemiological figures. The cohort included post-mortem tissue data from 387 players alongside historical metrics, age at death, and known rates of mild cognitive impairment and dementia in older players across 1,966 unexamined cases.

Direct neuropathological evaluation revealed CTE lesions in 93% of the donated brain specimens. By comparison, CTE markers occur in only about 1% of non-athlete brain tissue collections across facilities in the United States, Austria, and Brazil, according to the researchers.

Pathology and clinical status

Not all individuals with neuropathological changes exhibit symptomatic impairment during life. The study calculated that approximately 27% of the evaluated players likely had clinical dementia gigazine.netgigazine.netgigazine.netOpen source ↗. Tripodis emphasized that the 74.5% prevalence figure remains a statistical estimate, as diagnostic tools cannot yet detect CTE pathology in living patients.

Responding to the findings, an NFL representative stated that the league continues to develop technical and regulatory strategies intended to mitigate concussions and repetitive impacts.