What biological age is
Ageing is a biological process that plays out at the cellular level — independent of the pace at which a calendar moves. The hallmarks of aging (López-Otín et al., Cell, 2013, updated 2023) describe nine underlying processes including genomic instability, epigenetic changes, mitochondrial dysfunction and chronic inflammation.[6,8]
Biological age tries to summarise that underlying state in a single number. The idea is straightforward: instead of waiting for the outcome (disease, mortality), you estimate how biologically old your systems are right now based on objective markers — and therefore the direction you're heading.
How the clocks work
First-generation clocks — Horvath (2013) and Hannum — read patterns of DNA methylation at hundreds of sites across the genome. Those patterns shift systematically with age and serve as an accurate biological counter.[1,5]
Second-generation clocks went a step further. PhenoAge (Levine, 2018) and GrimAge (Lu, 2019) weren't trained on calendar age but on outcomes that actually matter: mortality, disease onset and healthspan. As a result they say not just 'how old you are' but how high your risk of early outcomes is right now.[2,3]
The newest clock, DunedinPACE (Belsky, 2022), measures not your age but the pace at which you're currently ageing — expressed as biological-years-per-calendar-year. A score of 1.2 means you age 1.2 biological years per calendar year; 0.8 means you're slowing down.4
PhenoAge — a clock from your blood
Not every clock requires DNA methylation. PhenoAge can also be computed from standard blood markers using nine values: albumin, creatinine, glucose, CRP, alkaline phosphatase (ALP), white blood cell count, lymphocyte percentage, MCV and RDW — plus your chronological age.2
That makes PhenoAge practical: these markers sit inside a standard blood panel. The Optimize Baseline measures all of them and computes the result for you. It isn't a perfect number — it speaks to systemic health rather than nuclear-clock biology — but it's one of the best-validated 'blood-age' estimates and it moves with lifestyle.
What moves the clock
The short answer: the same things the other guides come back to. Sleep, exercise (both aerobic and resistance), dietary pattern (Mediterranean has the strongest signal), weight management, not smoking, moderate alcohol, and stress management.[7,8]
The new part is that this is measurable. Classic lifestyle advice now has a feedback loop through biological age: keep doing the things the literature backs, and you see your PhenoAge drop relative to your chronological age. Stop doing them, and it climbs. That makes long-horizon behaviour considerably easier to sustain.
What you can measure
For a first biological-age estimate, an extended blood panel that includes the PhenoAge components (albumin, creatinine, glucose, CRP, ALP, white blood cell count, lymphocyte percentage, MCV, RDW) is the most practical entry point. Strongly complementary: apoB and lipoprotein(a) for cardiovascular ageing; HbA1c for metabolic ageing.
Methylation clocks (Horvath / PhenoAge-DNAm / GrimAge) are more precise but more expensive and need a saliva or blood sample sent to a specialised lab. For most people, a good blood-derived PhenoAge plus a complete cardiovascular screen is the highest-yield start.
How to read the result
A biological age below your chronological age is a good sign — but it's a snapshot, not absolution. A biological age above your chronological age isn't a diagnosis; it's a signal that one or more underlying processes are elevated, and an invitation to look more precisely (cardiovascular? inflammation? metabolic?).
Geroscience — the idea that ageing itself is the common denominator behind most chronic disease — has moved from hypothesis to consensus within the scientific community over the past fifteen years.7 Biological age is the first measurable bridge across.
When to involve a physician
An off biological age on its own isn't a reason to book the GP — but the underlying markers can be. At Optimize every result is triaged by our physician; if there are underlying values that warrant follow-up (e.g. abnormal kidney function, markedly elevated CRP, or concerning lipids) we reach out proactively.