Nearly 3 in 4 former NFL players likely had CTE at death, landmark study finds

A groundbreaking study published in JAMA Network Open estimates that roughly 3 in 4 former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy (CTE) — and that's after accounting for a major flaw in prior research. Earlier studies relied solely on donated brains, but players with cognitive symptoms were about five times more likely to donate, inflating prevalence rates. Boston University researchers corrected for this "selection bias" and still arrived at a striking 74.5% CTE prevalence.

The study analyzed 2,362 deceased former NFL players, of whom 396 were brain donors. Among donors with a confirmed CTE status, 93.5% tested positive. Even the most conservative sensitivity analysis placed CTE prevalence at 63.7% — a figure researchers themselves called "shocking." Importantly, having CTE neuropathology doesn't automatically mean a player experienced symptoms while alive.

By the Numbers:

• 74.5% — bias-adjusted CTE prevalence among deceased former NFL players
• 63.7% — conservative lower-bound estimate
• 93.5% — CTE rate among brain donors with confirmed status
• 27.2% — estimated prevalence of all-cause dementia during life
• 5x — how much more likely symptomatic players were to donate their brains

Why it matters: This is the first study to rigorously account for brain donation bias in CTE research, making it the most reliable population-level estimate to date. The findings have broad implications — not just for NFL players, but for athletes in contact sports at all levels, and for public health conversations around tackle football safety.