Seems then, that we need a good way to measure health span.
If we could define it we could measure it.
If I can perform daily activities particular to my lifestyle, and meet the cognitive and physical demands they place upon me, with no or limited compensating assistance, I probably am still in the ‘healthspan’ segment of my life.
If I end up in a wheelchair and/or don’t know what day it is, I’m probably out of the ‘healthspan’ segment.
Good enough for me, But I’m pretty low-IQ, and easily satisfied with simplistic concepts like the above.
I like your definition, but how much decline in function to we accept over time?