I think you might have a bunch of us who are in the late 50s early 60s for info, but... 80 is another thing entirely. I'm watching a few of my older friends deal with the issues of 78~85, and their experience is a good deal outside my own. Not being able to trust your brain to lift your left foot over that curb, even though the right foot managed it just fine, a microsecond ago. My aunt described it as "unlearning how to walk" and it's... one's brain starts to forget things that one takes totally for granted, until they can't be anymore.

Not sure if that's at all helpful, but your post made me think, certainly.