Study estimates 75% of NFL players who died over 15-year span had CTE

A new study found that an estimated 75% of professional football players who died over a 15-year span had signs of chronic traumatic encephalopathy (CTE), triple the estimate from a previous study conducted five months earlier. CTE, caused by repeated head impacts, can lead to cognitive decline, memory loss, depression, and mood swings, though not all people with CTE develop symptoms. The condition can only be diagnosed through autopsy, making it difficult to study prevalence accurately and creating potential bias in research since families of symptomatic players are more likely to donate brains for study.