Table 2.

The selection criteria for aging biomarkers among MLR, PCA, and KDM.

Selection criteria	Assessment Methods
Significantly correlated with CA	MLR (3, 13, 14, 20–22, 27, 32, 35, 40, 45, 54), PCA (3, 4, 10, 16, 18, 19, 23–26, 28–30, 35, 40, 45, 54), KDM (3, 34, 35, 40, 45, 54)
Non-redundant variables	MLR (35, 40, 45), PCA (4, 10, 16, 25, 26, 28–31, 35, 36, 40, 45), KDM (35, 40, 43, 45)
Used in previous studies	MLR (3, 22, 27, 32, 54), PCA (3, 54), KDM (3, 33, 37–39, 42–44, 48, 54)
Monitors the underlying mechanisms of the aging process rather than the effects of disease	MLR (20, 32, 35, 40), PCA (29, 31, 35, 40), KDM (35, 40, 43)
Repeatable measurements	MLR (14, 35), PCA (35, 46), KDM (35, 38, 46)
Reflects different organs or physiological functions	MLR (13, 15, 54), PCA (15, 23, 54), KDM (38, 54)
Variables with higher loadings within the first principal component	MLR (3, 15), PCA (3, 10, 15), KDM (3)
Test results can be quantified	MLR (35), PCA (16, 30, 31, 35, 46), KDM (35, 46)