Interactive: 74.5% — how researchers estimated CTE among NFL players who died from 2008 to 2023, step by step

A new study estimates that 74.5% of former NFL players who died from 2008 to 2023 had chronic traumatic encephalopathy, or CTE, a degenerative brain disease linked to repeated head impacts that can only be confirmed after death.

Hall of Fame Steelers center Mike Webster died in 2002 at 50. Pathologist Bennet Omalu examined his brain and in 2005 published the first description of CTE in a former NFL player. In 2013 the league agreed to a settlement with former players over concussions.

Earlier figures came from donated brains, such as 345 of 376 in 2023, and families who saw symptoms were more likely to donate. The new study used death records for all 2,362 players who died over 16 years: 396 donors and 1,966 who never donated.

Players with cognitive symptoms were about five times as likely to be donated. The researchers used that ratio to scale the donor rate to everyone. The estimate’s range runs from 69.6% to 78.3%, and the most conservative version is 63.7%.

The figure applies only to former players after death. It does not predict CTE in living players or say anything directly about active ones. The league points to padded practice caps, newer helmets and kickoff changes, while game concussions rose from 129 to 168 in 2025.