 Epigenetic clocks are one of the most effective tools we have for estimating biological age. They can be extremely useful in figuring out whether a lifestyle choice or therapeutic intervention increases or decreases biological age compared to chronological age. For that to really make sense, epigenetic clocks should also be good predictors of things like longevity and mortality. In other words, if an epigenetic clock says you're biologically younger, that should mean you'll live longer.