Epigenetic clocks, telomere length, proteomics, metabolomics — multiple methods claim to measure biological age. Here is what each measures, how they compare, and what they cannot tell you.
Biological age — the concept that two people of the same chronological age can have measurably different levels of physiological aging — is one of the most important and most abused concepts in longevity medicine.
The appeal is obvious: if we can measure biological age, we can track whether interventions are slowing aging in individual patients. But the measurement science is considerably less mature than its commercial applications suggest. Different biological age tests measure different things, correlate imperfectly with each other, and have different levels of validation as predictors of the outcomes that actually matter — mortality, disease incidence, and functional decline.
Epigenetic clocks (Horvath, GrimAge, PhenoAge, DunedinPACE): trained on DNA methylation patterns to predict chronological age or mortality risk. GrimAge and DunedinPACE have the strongest association with mortality in population studies. Sensitive to technical batch effects — measurements can shift due to sample preparation, not biology. Telomere length: shorter telomeres associated with aging and mortality risk in epidemiological studies. High within-individual variability; poor individual-level predictor. Proteomics (SomaScan, Olink): protein levels change with aging; some panels show strong mortality prediction. Expensive. Metabolomics: metabolite profiles change with age. Less developed for longevity prediction than proteomics.
No currently available biological age test has been validated to predict individual outcomes with clinical-grade accuracy. Population-level associations between biological age measurements and mortality risk do not translate to reliable individual-level predictions. More importantly, no biological age test has been validated as an intervention outcome measure — it has not been demonstrated that reducing your biological age score on any current test translates to reduced mortality. This is the critical gap between the science and the commercial applications of biological age testing.
Biological age measurement is a legitimate and important area of aging research. Current tests have meaningful population-level predictive validity. What they do not have is validated individual-level prediction or demonstrated utility as intervention outcome measures. A physician ordering biological age testing for a patient should communicate that the results provide directional information about physiological aging — not a precise individual prediction of mortality, and not a validated measure of whether an intervention is working.
This information is provided for educational reference only and does not constitute medical advice or a treatment recommendation.