A study published in The BMJ has found that roughly one in four former NFL players could develop chronic traumatic encephalopathy (CTE), the degenerative brain disease linked to repeated head impacts, at some point in their lives. Researchers examined the brains of 878 former players who died between 2016 and 2021 and found evidence of CTE in at least 215 of them, though the true rate is likely higher since 643 brains were never examined. The findings have prompted renewed calls for the NFL to go further in protecting players from cumulative, repetitive head trauma, not just diagnosed concussions.

The 24.5% prevalence rate, if applied to the NFL's current 1,696 active roster spots across all 32 teams, would suggest around 415 players might eventually develop the disease. CTE can currently only be confirmed after death and causes symptoms including memory loss, mood swings and erratic behaviour; it first gained public attention in football after diagnoses in former players such as Junior Seau and Mike Webster. Neurosurgeon Dr Julian Bailes, a pioneer of CTE research who was portrayed in the film "Concussion", said the study "should be a call to action for everyone involved in football," urging further advances in rules, training and equipment to reduce cumulative brain impacts rather than treating safety as an "all or nothing" issue.