At Least One in Four NFL Players May Have CTE

“Among the people who did not donate,” he says, “16% had dementia listed on their death certificate. That certainly does not mean they had CTE, but it illustrates how unrealistic it is to assume that every non-donor was disease-free.”

Another part of the study looked at a larger time window—from 2008 to 2021—during which 1,712 former NFL players died. Of those, 338, including the 235 already analyzed, donated their brains to research, and of that group, 315 had CTE. That makes for a possible CTE prevalence of as high as 93.2%, though if the researchers once again made the conservative—if unrealistic—estimate that all of the unexamined brains were disease-free, the figure would drop to 18.4%.

What makes CTE particularly insidious is that it is a cumulative disease, one that builds up over a career’s-worth of hits that don’t begin when a player is tapped for the NFL, but can stretch back into college, high school, and even childhood play. In 2011, the NFL, mindful of the growing incidence of CTE, established its concussion protocol, sidelining players who take a hit and exhibit any signs of possible concussion, such as confusion, amnesia, ataxia—a lack of muscle control—or any loss of consciousness.