It could be true, but I find other personality changes more obvious among my older friends. Nonstop talking, more of a propensity to anger, disregard for the needs of others (even among those who had been the opposite before), suspicion of the motives of others, a worried disposition toward life instead of joie de vivre . . .
These are more noticeable if you know someone well. Putting dirty clothes in the freezer, getting lost when out walking, and stuff like that is quirky but there are other signs that seem more gradual and subtle and antisocial.
The trait that freaks me out is when someone who used to be highly intelligent and logical start contradicting themselves less than a minute after they make statements—have a relative like that now...