Believe it. I know a handful of ex-players who were articulate when younger, now in their 50’s cannot make a coherent sentence or remember events that happened not too long ago.
Yep - we just buried one of my best friends (who played on the offensive line in college with me) as he passed away from dementia in his 40’s. There is no way to prove that this was caused by football...but there’s not a whole bunch of people being diagnosed with dementia in their 30’s.