Epigenetic Age: What It Actually Measures

Epigenetic age has become the marquee metric of longevity medicine — and, unfortunately, one of the most misunderstood. In this essay we separate the three most-cited clocks and explain which ones actually respond to protocol.

Horvath's multi-tissue clock (2013) trained on methylation at 353 CpG sites and predicts chronological age with remarkable accuracy. It is a static reference, not a moving target — its stability is the point.

GrimAge, developed by Lu and Horvath in 2019, is different. Trained on mortality prediction rather than age, it responds to lifestyle, inflammation and cardiovascular load. A four-year reduction over twelve months, as we see in the majority of our members, is meaningful.

DunedinPACE, more recent still, estimates the rate of biological aging — how fast you are currently aging, rather than how old your biology is. It is the single most sensitive metric to intervention in our clinic.

The practical implication: run all three. Use Horvath as your baseline, GrimAge for medium-term protocol response, and DunedinPACE as your steering wheel.