San Francisco 49ers players practice at Levi’s Stadium in Santa Clara on May 28. A recent study found that 1 in 4 former NFL players will end up with chronic traumatic encephalopathy, a brain disease known as CTE.

A new study showing that at least 1 in 4 people who have played in the NFL will end up with chronic traumatic encephalopathy is just the latest sobering dose of reality for our football-obsessed culture. 

The brain disease, known as CTE, is caused by repeated hits to the head, and it is highly prevalent in former NFL players. We’ve learned this by studying the brains of those who have recently died because we still can’t diagnose the disease while someone is alive.

Through building one of the most ambitious brain donation programs in the world at the Boston University CTE Center and the Concussion & CTE Foundation, we proved that 25% to 98% of NFL players who died between 2016 and 2021 had the disease: 878 players died over those six years, 235 brains were studied and 215 (91%) had it. The findings are sobering for NFL players, but they are also concerning for everyone who plays tackle football because we don’t yet know how to cure CTE.

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Related reading: Experts and parents — including an ex-49er — question youth football safety after CTE study

And the athletes aren’t just statistics — the last person included in the study, Chris Eitzmann, was my roommate and captain when we played football for Harvard University. He passed away at the age of 44 due to heavy drinking that helped him cope with his hidden brain injuries. 

It may be hard for many football fans to hear, but we already know........

© San Francisco Chronicle