Study estimates 74.5% of deceased former NFL players had CTE

A study estimates that 74.5% of deceased former NFL players had chronic traumatic encephalopathy, or CTE, after researchers adjusted for potential bias in brain donations, according to ABC7 Los Angeles. The researchers cautioned that the findings may not represent living NFL players.

CTE is associated with repeated head impacts and can be diagnosed only after death. Accounting for which families donate brains helps researchers assess how much those donations may skew estimates of the disease's prevalence.

The study, published in the Journal of the American Medical Association, examined 2,362 deceased former NFL players, ABC7 Los Angeles reported. Researchers analyzed 396 players whose brains were donated and 1,966 whose brains were not.

CTE was identified in 93.5% of brain donors. Researchers estimated that families who had noticed cognitive symptoms were about five times as likely to donate a brain, then adjusted their analysis for that potential bias to reach the 74.5% estimate.

The researchers also estimated that 27.2% of the deceased former players had experienced dementia during their lives. They said that estimate likely understates dementia's prevalence.

Yorghos Tripodis, a Boston University professor of biostatistics and a study author, told ABC News that the group's earlier research had placed possible CTE prevalence between 25% and 98%. He said the new analysis could not eliminate every potential bias, but its estimate remained at or above 60% even under very conservative assumptions.

The NFL Players Association expressed support for research into football's long-term health effects, according to ABC7 Los Angeles. The NFL said it continues efforts to limit concussions and head impacts.

The estimates concern deceased former NFL players, not everyone who has played football. Researchers cautioned against treating the findings as representative of living NFL players.