Measuring aging: biological age and its biomarkers
Epigenetic clocks, fitness, grip strength and walking speed: what they measure and how much to trust them.
VALREXA Biosciences · 8 min read · November 2026
- Biological age tries to measure how fast a body is aging, separate from birthdays.
- Epigenetic clocks are powerful research tools but are not yet validated for guiding personal treatment.
- Simple functional measures, such as fitness, grip strength and walking speed, strongly predict health outcomes.
Chronological versus biological age
Two people born the same year can age at very different rates. A biomarker of aging is a measurement that tracks this biological rate and predicts future health better than age alone.
Epigenetic clocks
In 2013 Steve Horvath built a “clock” from DNA methylation, chemical tags on DNA, at 353 sites that estimated age across many tissues. Later clocks were trained to predict health outcomes rather than age: PhenoAge, GrimAge and DunedinPACE, which estimates the pace of aging. These are widely used in research.
Functional biomarkers
| Measure | What it reflects | Evidence |
|---|---|---|
| Cardiorespiratory fitness (VO₂max) | Heart, lung and muscle capacity | Strongly and inversely linked to death rates in large cohorts |
| Grip strength | Overall muscle strength | In the 17-country PURE study, lower grip strength predicted higher mortality and cardiovascular death |
| Gait (walking) speed | Integrated health of many systems | Pooled cohorts link faster gait speed to longer survival in older adults |
| Chair-rise and balance tests | Leg strength and stability | Predict falls and disability |
Blood and clinical markers
Routine measures such as blood pressure, HbA1c, lipids, kidney function and inflammatory markers like C-reactive protein also track risk. Researchers combine many of them into composite scores.
What makes a good biomarker?
- It predicts outcomes better than chronological age.
- It is reliable: the same person gets similar results on repeat tests.
- It responds to interventions in a way that matches real changes in health.
- It is validated in large, diverse populations.
Few markers meet all four today, which is why biomarker validation is a major research field.
Sources and further reading
- Horvath 2013. DNA methylation age of human tissues and cell types. Genome Biology
- Belsky et al. 2022. DunedinPACE. eLife
- Leong et al. 2015. Grip strength, PURE study. Lancet (PubMed)
- Studenski et al. 2011. Gait speed and survival. JAMA (PubMed)
- Mandsager et al. 2018. Cardiorespiratory fitness and mortality. JAMA Network Open (PubMed)
VALREXA Biosciences. (2026, November 7). Measuring aging: biological age and its biomarkers. VALREXA Biosciences. https://valrexa.com/longevity/biomarkers-of-aging.html
APA style · Last reviewed November 7, 2026 · Our editorial standardsEducational content, not medical advice. Talk to a qualified healthcare professional before making changes to your health routine.