BackgroundEpigenetic clocks are DNA methylation-based biomarkers increasingly used in aging research and clinical trials. A recent assessment of 18 clocks across multiple short-term perturbations concluded that most demonstrate only moderate biological reliability, raising concerns about their translational utility. However, epigenetic clocks differ substantially in their construction and in the biological signals they capture, and their sensitivity to physiological perturbation may not be a flaw but a consequence of the construction. To understand this more clearly, we undertook a focused investigation of biological reliability for a single, well-characterised perturbation, an overnight fast followed by acute refeeding, examining how and why clock estimates may shift with physiological state.
MethodsWe evaluated 24 epigenetic clocks spanning five construction categories - first and second generation classical clocks (eg. Horvath, Hannum, PhenoAge), the PC versions of the classical clocks, SystemsAge organ-system clocks, mortality-trained clocks (GrimAge, PCGrimAge, OMICmAge), pace of aging clocks (DunedinPACE) and the IntrinClock, across three datasets: a within-person paired fasting design (n = 15 pairs), a cross-sectional cohort of fasted vs non-fasted (n = 2,895), and EPICv2custom technical replicates (n = 96 samples from 4 individuals). For each clock, we quantified the acute fasting effect with and without immune cell adjustment, decomposed between-person and within-person variance at successive adjustment levels (Raw, EAA, IAA), and benchmarked biological variability against the technical measurement floor.
Seale, K. B. et al. · CC-BY 4.0