A perspective piece in Rejuvenation Research challenges the field's foundational vocabulary, arguing that 'biological age' and 'health' are functionally interchangeable concepts in most clinical contexts — both resist single-biomarker quantification, both describe multidimensional physiological states, and both currently exist as abstractions rather than measurable quantities. The author, affiliated with longevity startup Tally Health, contends that biological age holds a future advantage over composite health indices precisely because it maps onto an intuitive, familiar numerical scale that patients and clinicians can immediately interpret.
This commentary arrives at a critical moment in aging science. The proliferation of epigenetic clocks — Horvath, GrimAge, DunedinPACE — has created a marketplace of biological age estimates that often disagree with each other by years, raising legitimate questions about what exactly is being measured. The author's core insight is underappreciated: calling someone 'biologically 45' communicates nothing more precise than calling them 'healthy for their age' until the underlying measurement infrastructure matures. The healthspan-versus-lifespan divergence example is particularly sharp — a compressed morbidity scenario where someone dies young but lived vigorously exposes the conceptual seam between the two constructs. The practical implication for adults investing in longevity interventions is sobering: current biological age tests may be rebranding existing health assessments rather than revealing something genuinely novel. This is an editorial rather than empirical work, limiting its evidential weight, but its philosophical precision makes it a necessary corrective to overclaiming in the biological age testing industry.
