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

An estimated 75% of professional football players who died over a 15-year span had signs of chronic traumatic encephalopathy, or CTE, a study published Wednesday found. It’s the highest estimate to date. Most recently, a study published in August by the same group estimated that one-quarter of NFL players who died in a five-year span had CTE. The new study, published in JAMA Network Open, put the figure at three times higher. Not all people with signs of CTE in the brain go on to experience cognitive decline or dementia, and some people may never experience symptoms at all. A smaller proportion of the former players in the analysis were estimated to have dementia, about 27%, the study found.

The results were surprising, said study leader Yorghos Tripodis, the director of statistics and data management at the Boston University Alzheimer’s Disease and CTE Center. Boston University houses the UNITE Brain Bank, which studies the effects of repetitive head trauma in donated brains, including the brains of athletes, military personnel and others. “I had to double-check the numbers,” Tripodis said. Still, he said, the number is a best guess. “Right now we don’t know how to diagnose CTE when people are alive, so we are trying to estimate.” In an emailed statement, an NFL spokesperson said, in part, that the league