Aging is a global phenomenon of damage accumulation throughout the body: more damage means faster aging. People who show more damage in any one measure tend to show more damage in all the others too, as it all stems from a few root causes. This bears up in epidemiological studies, but there is a fair amount of individual variation.

Almost every decline in aging that can be measured can be correlated with near future mortality. Grip strength and walking speed are the common ones presently used, and finding others should be in no way surprising.