How sad.
Sometimes it's a total surprise, but for those "fortunate" enough, to have a warning, they need to take it seriously -- and not just those to whom it happens, but the doctors, who also usually just brush it off.
But .. dementia is a series of miniscule strokes - which show no outward physical signs.
I can tell when my mom is having an episode - but it's only because of her actions - which don't ever seem to exhibit typical stroke symptoms. She's agitated and walks back and forth to my room at 10-15 min intervals. Can't tell me what she wants - or says she wants nothing. Then she turns around and walks back to the living room where she sits in her chair and continues watching her TV.
I have at times noticed a sluring of her speech - but not during her walking back and forth.