What it is
Biological age is an attempt to express how old you are physiologically — using biomarkers like an epigenetic clock, blood panels or functional tests — rather than the years since birth (chronological age).
Why it matters for longevity
If biological age can be measured reliably, it could act as a near-term readout for whether an intervention is helping, instead of waiting decades for mortality data. It ties many of the hallmarks of aging into a single number.
What the evidence shows
Different clocks and panels disagree, can be noisy at the individual level, and few are validated to *change* outcomes when you act on them. They are valuable research tools and improving fast, but a single “biological age” result should be read as an estimate, not a verdict.
How we use it
We treat biological-age measures as supportive signals and weight hard outcomes and well-validated risk markers more heavily.