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Biological age clocks

Trajectory beats snapshot; a clock reading is a risk estimate, not a verdict.

Updated 14 Oct 202614 sources7 min read
Short answer

Epigenetic clocks are regression algorithms that read age-related DNA-methylation drift and output a biological age or aging rate. Three large 2025–2026 analyses, an 18,859-person head-to-head, a 24-year longitudinal study, and a NHANES mortality analysis, confirmed GrimAge-family and DunedinPACE as genuine risk stratifiers. The caveats: clocks disagree with each other, single measurements are noisy, and no intervention has yet proven that moving a clock changes lifespan.

Summary drafted from this entry’s sources; editorial review pending.

01Key questions

Do biological age tests actually measure aging?

They measure methylation patterns trained against health outcomes. GrimAge v2 and DunedinPACE showed the largest effects among 14 clocks tested against 174 outcomes in Generation Scotland, real risk stratifiers, not deterministic organ age.16

Which biological age clock is best?

It depends on the question: DunedinPACE answers 'how fast am I aging' with the highest test-retest reliability; GrimAge V2 answers 'how much damage has accumulated.' Multi-omic clocks like OMICmAge may outperform both but are earlier.418

Can supplements lower your biological age?

Almost nothing has credible clock data. The best RCT result is semaglutide slowing five clocks including a 9% DunedinPACE drop in an 84-person HIV cohort; rapamycin's PEARL trial was null. Most supplement claims are unsupported.1212

Is one biological age test enough?

No. Single readings carry assay noise and clocks disagree. The entry notes same-provider retests at 6–12-month intervals read as a trajectory, and notes no clock is FDA-cleared as a diagnostic.9

DNA-methylation "clocks" are the de facto surrogate endpoints of longevity medicine — used to price DTC tests, market interventions, and adjudicate trials — yet their validation picture changed materially between Dec 2025 and Mar 2026. Large head-to-head and longitudinal studies confirmed GrimAge-family and DunedinPACE as genuinely predictive of disease and mortality, while simultaneously exposing their limits (single timepoints, assay noise, clock disagreement, zero clinical-grade standardization). Trajectory beats snapshot; nothing about a clock reading is destiny.

02What Clocks Actually Measure

Epigenetic clocks are regression algorithms that estimate biological age (or aging rate) from DNA methylation at hundreds of CpG sites in blood/saliva. Methylation drift is systematic with age — the clock reads the drift. Different clock generations answer different questions:

Generation Clocks Question answered Analogy
1st (2013–14) Horvath, Hannum "How old does methylation say you are?" Odometer (chronological fit)
2nd (2018–19) GrimAge (v1/v2), PhenoAge "How much mortality/disease risk is in your methylation?" Damage gauge (trained on outcomes)
3rd (2020–22) DunedinPoAm → DunedinPACE "How fast are you aging right now?" Speedometer (longitudinal rate)
4th / multi-omic + retroelement (2025–26) OMICmAge, RetroAge, DNAmEMRAge, EpiAge-R concept "Integrate omics + EMR + retroelements into one systems readout; add resilience" Fleet telemetry (in development)

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Design notes that matter for interpretation: - GrimAge trains on DNAm surrogates of plasma proteins + smoking pack-years — it captures cumulative damage including smoking history (predictive even in never-smokers via protein surrogates). Latest version: GrimAge V2 (Aging 14:9484–9549, 2022; DOI 10.18632/aging.204434). Original: Lu et al., Aging 11:303–27, 2019 (DOI 10.18632/aging.101684). - PhenoAge was built from clinical chemistry biomarkers, then methylation-mapped (Levine et al., Aging 10:573–91, 2018; DOI 10.18632/aging.101414). - DunedinPACE was trained on observed 12-year change in 18 organ-function biomarkers in the Dunedin birth cohort (Belsky et al., eLife 11:e73420, 2022; DOI 10.7554/eLife.73420; predecessor DunedinPoAm, eLife 2020; DOI 10.7554/eLife.54870). Score of 1.0 = cohort-average pace; >1 = faster aging. It has the highest test-retest reliability of any clock — the reason it dominates intervention trials.

03Validation Status: The Dec 2025 – Mar 2026 Trilogy

Three Nature-portfolio analyses landed in one quarter, collectively the strongest validation — and the clearest caution — to date:

  1. Head-to-head (Generation Scotland, n=18,859): Mavrommatis et al. compared 14 clocks against 174 incident disease outcomes + all-cause mortality. 176 disease associations across 13 clocks; GrimAge v2 and DunedinPACE showed the largest effect sizes; respiratory and liver outcomes were the strongest predictive domains; e.g., DunedinPACE HR 1.44 for incident diabetes (Nat Commun 16, 2025; PMID 41402269; PMC12708718).
  2. Longitudinal trajectories (InCHIANTI, n=699, up to 24-year follow-up): Kuo et al. (2026) showed that adding rate-of-change to baseline GrimAge/GrimAgeV2/PhenoAge/DunedinPACE improved mortality prediction to C-statistics of 0.800–0.808 — measurable discrimination gains from modeling trajectories rather than snapshots.
  3. Population mortality (NHANES, n=2,105, median 17.5-year follow-up, 998 deaths): among all clocks examined, GrimAge epigenetic age acceleration was the most statistically significant predictor of mortality (p<0.0001) after standard covariate adjustment (Geroscience, 2025).

Consensus reading: 2nd/3rd-generation clocks are real risk stratifiers — comparable to or better than conventional risk factors for several outcomes. They are not deterministic organ age, they disagree with each other (partially non-overlapping variance), and single readings carry assay noise that marketing omits.

The frontier: multi-omic and resilience

  • OMICmAge integrates multi-omics with electronic medical records into a single biological-age readout; outperformed prior methylation-only clocks on precision and 5-/10-year mortality discrimination in head-to-head analysis (Nat Aging, 2026; DOI 10.1038/s43587-026-01073-7).
  • EpiAge-R framework (Yamada, Int J Mol Sci 27:1908, 2026; PMID 41752045, PMC12940517): clocks are odometers or speedometers but measure no resilience — the capacity to recover homeostasis after stress. Two people with identical GrimAge and DunedinPACE can diverge sharply after surgery or infection.
  • AmiAge — amino-acid biological-age clock (Nat Commun 17:6733, 2026; DOI 10.1038/s41467-026-73371-y): Random Forest regressor trained on plasma concentrations of 18 amino acids (n = 11,000 in-house + 270,000+ public samples, ages 1–89). The AmiAge Gap correlates with frailty index, telomere length, age-related disease incidence, and mortality. Distilled to an 8-amino-acid clinical panel: alanine, glutamine, glycine, histidine, leucine, phenylalanine, tyrosine, valine. Notably taurine is one of the 18 input features but drops out of the distilled panel — consistent with the de Cabo 2025 + Marcangeli 2025 finding that taurine alone is not a primary aging biomarker; its signal is redundant with BCAAs at the population level. Implication: panel >> single amino acid for biological-age tracking; commercial metabolomics-grade amino acid panels are the natural extension of methylation clocks for users who can't access venipuncture-based assays. See Taurine - The Aging Amino Acid for the full biomarker debate.

04What Has and Hasn't Moved Clocks (Honest Intervention Ledger)

Intervention Clock result Read
GLP-1 agonist (semaglutide, 32 wk Ph2b RCT, NCT04019197, n=84 PWH) DunedinPACE −9% (p=0.01); PhenoAge −4.9 yr (p=0.004); PCGrimAge −3.1 yr (p=0.007); GrimAgeV2 −2.3 yr (p=0.009); OMICmAge −2.2 yr (p=0.009); RetroAge −2.2 yr (p=0.030) Best RCT clock data to date — 5/5 clocks significant across 1st–4th gen. Liver-fat responders drove the signal — see GLP-1 Peptides (Semaglutide, Tirzepatide, Retatrutide). Corley MJ et al., Nat Commun 17:6606, 2026. PMID 42156721 · PMC13381876.
Rapamycin (PEARL, TruAge clocks, n=24) Null (mixed, non-significant) Absence of evidence ≠ evidence of absence; assay + n issues — see Rapamycin mTOR Inhibition - PEARL Trial Evidence
Therapeutic plasma exchange (first human RCT 2025) Mixed across 36 clocks Signal, not proof — see Therapeutic Plasma Exchange (TPE)
Caloric restriction (CALERIE) DunedinPACE slowed vs. control Slow aging rate with sustained CR
Taurine (NCT06613542) Pending — first taurine RCT with clock endpoints See Taurine - The Aging Amino Acid
Most supplements No credible clock data Marketing claims unsupported

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⚠️ Surrogate-endpoint caveat: no intervention has yet shown that changing a clock score changes lifespan or healthspan. Clocks are the best available intermediate endpoint, not proof of slowed aging.

05Practical Measurement Guide

Which test: - Rate question ("am I aging fast?") → DunedinPACE-based panel (e.g., TruDiagnostic, Tally Health DTC offerings). - Risk question ("accumulated damage?") → GrimAge V2 / PCGrimAge. - Organ-specific methylation clocks (brain, heart, kidney ages) exist; treat as exploratory.

Interpretation rules: 1. Trajectory > snapshot. Retest at 6–12-month intervals; one reading is noise-prone. 2. Compare like assays only. Different labs/platforms are not interchangeable; stay with one provider for longitudinal tracking. 3. Effect sizes in trials are small (single-digit % pace changes). A DTC report claiming years of reversal from a supplement protocol is marketing. 4. Anchor to functional markers. Pair with VO2max, DEXA, ApoB, HbA1c, hs-CRP (see Overview - Longevity Science biomarker table). 5. No regulatory clearance: as of 2026 no clock is an FDA-cleared in-vitro diagnostic; results are wellness-grade.

06Connections

Neighborhood · 8 linked entriesOpen full map →
Longevity scienceGuide · 32 links→ NAD+Compound · 32 links→ Biohacking and optimizationGuide · 21 links→ Hallmarks of agingMechanism · 17 links→ RapamycinCompound · 14 links→ TelomeresMechanism · 14 links→ GLP-1 agonistsCompound · 13 links→ KlothoMechanism · 12 links→

07Sources

  1. Lu AT, et al. DNA methylation GrimAge version 2. Aging 14(23):9484–9549, 2022. DOI 10.18632/aging.204434 .DOI 10.18632/aging.204434
  2. Lu AT, et al. DNA methylation GrimAge strongly predicts lifespan and healthspan. Aging 11(2):303–27, 2019. DOI 10.18632/aging.101684 .DOI 10.18632/aging.101684
  3. Levine ME, et al. An epigenetic biomarker of aging for lifespan and healthspan (PhenoAge). Aging 10(4):573–91, 2018. DOI 10.18632/aging.101414 .DOI 10.18632/aging.101414
  4. Belsky DW, et al. DunedinPACE, a DNA methylation biomarker of the pace of aging. eLife 11:e73420, 2022. DOI 10.7554/eLife.73420 .DOI 10.7554/eLife.73420
  5. Belsky DW, et al. DunedinPoAm, quantification of the pace of biological aging. eLife 2020. DOI 10.7554/eLife.54870 .DOI 10.7554/eLife.54870
  6. Mavrommatis C, et al. An unbiased comparison of 14 epigenetic clocks in relation to 174 incident disease outcomes. Nat Commun 16, 2025. PMID 41402269 .PubMed 41402269
  7. PMC12708718PMC12708718
  8. OMICmAge quantifies biological age by integrating multi-omics with EMRs. Nat Aging , 2026. DOI 10.1038/s43587-026-01073-7 .DOI 10.1038/s43587-026-01073-7
  9. Yamada H. Epigenetic Clocks, Resilience, and Multi-Omics Ageing: the EpiAge-R Conceptual Framework. Int J Mol Sci 27(4):1908, 2026. PMID 41752045 .PubMed 41752045
  10. PMC12940517PMC12940517
  11. AmiAge — amino-acid biological age clock. Nat Commun 17:6733, 2026. DOI 10.1038/s41467-026-73371-y . Random Forest on 18 plasma amino acids (n>281,000); distilled 8-AA clinical panel (alanine, glutamine, glycine, histidine, leucine, phenylalanine, tyrosine, valine); taurine in full panel but drops out of distilled 8 — consistent with de Cabo 2025 + Marcangeli 2025 single-marker null.DOI 10.1038/s41467-026-73371-y
  12. Corley MJ, Dwaraka VB, Pang APS, et al. "Semaglutide slows epigenetic aging in a randomized trial of HIV-associated lipohypertrophy." Nat Commun 17:6606, 2026. PMID 42156721 · PMC13381876 · DOI 10.1038/s41467-026-72861-3 . Post-hoc analysis of NCT04019197 (32-wk, n=84 PWH; semaglutide n=45, placebo n=39). Significant slowing across PhenoAge −4.9y (p=0.004), PCGrimAge −3.1y (p=0.007), GrimAge V2 −2.3y (p=0.009), OMICmAge −2.2y (p=0.009), RetroAge −2.2y (p=0.030), DunedinPACE −9% (p=0.01) . First GLP-1 epigenetic-clock RCT; HIV-specific cohort limits generalizability; epigenetic endpoints were post-hoc. See GLP-1 Peptides (Semaglutide, Tirzepatide, Retatrutide) .NCT04019197 · PubMed 42156721 · PMC13381876 · DOI 10.1038/s41467-026-72861-3
  13. NCT06613542NCT06613542
  14. Marcangeli V, et al. "Experimental Evidence Against Taurine Deficiency as a Driver of Aging in Humans." Aging Cell 24(10):e70191, 2025. PMID 41061678 · PMCID PMC12507425 . Independent UQAM/McGill refutation of taurine as aging biomarker; n=137 men, ages 20–93, with DXA + pQCT + mitochondrial respiration endpoints. See Taurine - The Aging Amino Acid .PubMed 41061678 · PMC12507425

08Entry history

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