Epigenetic Clocks ("Biological Age" Tests)
DNA methylation patterns at specific genomic sites, combined by algorithm into an estimate of “biological age.” The best-known versions — the Horvath clock, GrimAge, PhenoAge and DunedinPACE — underpin most consumer biological-age tests. Methylation does change with age in a fairly predictable pattern, and some clocks, GrimAge and DunedinPACE in particular, correlate with future mortality and morbidity better than chronological age alone. That is a genuine and interesting finding about populations, which is not the same as a finding about you.
A 2026 review, “From population science to the clinic? Limits of epigenetic clocks as personal biomarkers,” concluded that epigenetic clocks fail to meet common standards for clinical utility compared with established biomarkers, and that applying them to individual-level decision-making can be uninformative and potentially harmful. It cites unresolved technical issues — clock construction methods, sample handling, computational implementation — alongside biological ones: tissue specificity, sensitivity to environmental and sociodemographic context, and limited replication across diverse populations. Its conclusion is that even if those hurdles are eventually cleared, epigenetic clocks as currently understood should not be used to make individual-level decisions.
"From population science to the clinic? Limits of epigenetic clocks as personal biomarkers." PubMed: PMID 41403206