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How we work

Our methodology

Intrinsic Age is editorially independent. We have no affiliate relationships, no sponsored placements, and no vendor partnerships. Here is exactly how we evaluate evidence.

Evidence tier framework

Every test, clock type, and intervention on Intrinsic Age is rated using our four-tier evidence framework. Tiers reflect the current state of published, peer-reviewed research — not marketing claims.

STRONG — Strong evidence

Strong evidence

  • Multiple peer-reviewed RCTs or large prospective cohort studies
  • Independent replication across different populations and labs
  • Consistent effect direction and meaningful effect size
  • Open methods allowing reproduction
  • Demonstrated incremental value beyond standard risk factors

Examples: Classic epigenetic clocks (Horvath, Hannum) for age prediction. Exercise and diet for epigenetic age deceleration.

PROMISING — Promising evidence

Promising evidence

  • Some RCTs or strong observational data
  • At least one independent replication or large-cohort validation
  • Plausible biological mechanism supported by data
  • Published methodology but may lack full independent reproduction
  • Vendor validation may be strong but independent confirmation is limited

Examples: GrimAge and DunedinPACE for mortality prediction. GlycanAge for inflammation tracking. Metformin for aging (pending TAME trial).

EMERGING — Emerging evidence

Emerging evidence

  • Animal studies, pilot human studies, or early-phase trials
  • Mechanistic plausibility but limited clinical data
  • No independent replication in humans yet
  • May be based on small sample sizes or vendor-only datasets
  • Exciting science but translation to clinical utility unproven

Examples: Partial cellular reprogramming. NAD+ precursors for biological age. Microbiome-based age clocks.

INSUFFICIENT — Insufficient evidence

Insufficient evidence

  • Vendor-only claims without published validation
  • No peer-reviewed studies or only vendor-funded studies without independent oversight
  • Marketing language exceeds published evidence
  • Proprietary models without methodological transparency
  • No independent replication or external validation

Examples: Products claiming age reversal without test-retest reliability data. Clocks comparing across different tissue types without calibration.

Editorial principles

No affiliate relationships

We do not receive commissions, referral fees, or any compensation from test vendors. Listings are not paid placements.

Honest about uncertainty

Following Kriukov et al. (2025), we emphasize that aging clocks have real limitations. We always note what a test cannot tell you, not just what it can.

Prioritize independent validation

Vendor-funded studies are noted as such. We weight independent, peer-reviewed replications more heavily than vendor claims.

Evidence tiers can change

As new research publishes, tiers are updated. A product rated EMERGING today may earn PROMISING or STRONG with new independent evidence.

How we classify methods

Beyond evidence tiers, we are systematically reviewing how biological age methods are categorized — distinguishing scientific method families from vendor marketing terms.

Read our classification approach →

The critical lens: “Do we actually need aging clocks?”

Our editorial framework is informed by Kriukov et al.'s 2025 perspective in npj Aging, which argues that many aging clocks rely on abstract definitions of biological age, have inconsistent clinical validation, and frequently ignore prediction uncertainty.

We take this critique seriously. For every test and clock type, we ask: Does this tool demonstrate a clear advantage over simpler alternatives? Is the uncertainty communicated? Has it been validated independently?

This does not mean clocks are useless — it means consumers deserve honest context about what these tools can and cannot do.