An estimated 74.5 per cent of former NFL players who died between January 2008 and December 2023 had chronic traumatic encephalopathy, or CTE, according to a Boston University study. Published in JAMA Network Open, the research provides the first population-level estimate for NFL players. Researchers also estimate that approximately one-quarter had dementia, a common feature of late-stage CTE.
The analysis covered more than 2,300 former players, including almost 400 whose brain samples were held in the university's UNITE Brain Bank. The remainder were identified through the US National Death Index. Families of players who experienced CTE-related symptoms were five times more likely to donate their relative's brain than families of players without such symptoms.
Accounting for that donation bias produced an estimate substantially below the 99 per cent reported in a 2017 analysis of donated brains. That earlier sample may have disproportionately represented players whose symptoms prompted their families to donate. Establishing the disease's true prevalence is important for understanding its public health impact, the researchers note.
CTE is a neurodegenerative disease associated with repeated head impacts and can currently be diagnosed only through an examination after death. Symptoms experienced during life can include memory difficulties, impaired concentration, depression and poor impulse control. In affected brains, a protein called tau forms abnormal, damaging clumps. Although identified most frequently among American football players, CTE can also occur in people exposed to other contact sports, intimate partner violence or military combat.
