What is the difference between chronological age and biological age?
Chronological age indicates the time elapsed since birth. Biological age, on the other hand, attempts to measure why individuals of the same chronological age may differ in terms of physiological reserve, disease risk, or rate of aging. A 2025 systematic review demonstrated that numerous different models exist for assessing biological age, and that the methods differ markedly in terms of the biomarkers used and their statistical structure.
What is clinical PhenoAge?
The Phenotypic Age approach developed by Levine and colleagues uses nine biomarkers obtainable from routine laboratories alongside chronological age to generate a phenotypic age estimate associated with mortality risk. In clinical practice, when “PhenoAge” is mentioned, it most often refers to this blood biochemistry-based model.
Which parameters does PhenoAge use?
- Albumin
- Creatinine
- Glucose
- C-reactive protein (CRP)
- Lymphocyte percentage
- Mean corpuscular volume (MCV)
- Red cell distribution width (RDW)
- Alkaline phosphatase (ALP)
- White blood cell count (WBC)
- Chronological age
The composite score formed by these parameters is converted into units of age based on mortality associations in a reference population. The result can provide a broader physiological picture than a single laboratory value; nevertheless, it is not an individual diagnosis of disease.
What does “PhenoAge 55, my actual age is 48” mean?
This result may suggest that, within the model used, the individual’s biomarker pattern resembles a risk profile associated with an older age in the reference population. It is not appropriate to interpret the difference definitively as “you are 7 years older.” Acute infection, elevated CRP, glucose control, kidney function, or hematological changes can influence the score; therefore, serial measurements and clinical context are important.
Are DNAm PhenoAge and clinical PhenoAge the same thing?
No, although their names are similar, they are not the same measurement. Clinical Phenotypic Age uses routine blood biomarkers. DNAm PhenoAge, on the other hand, is an epigenetic clock calculated from DNA methylation sites and developed to predict a phenotype associated with clinical Phenotypic Age. This distinction is especially important when evaluating commercial biological age tests.
What is an epigenetic clock?
Epigenetic clocks primarily use age-related patterns in DNA methylation. While first-generation clocks largely focused on predicting chronological age, next-generation models such as GrimAge, PhenoAge, or DunedinPACE were developed to link to outcomes such as health risk, mortality, or pace of aging. A 2025 review reports that newer-generation clocks may show stronger associations with health outcomes; which clock to use depends on the research or clinical purpose.
What is GrimAge?
GrimAge is among a family of epigenetic models aimed at generating an indicator of aging associated with mortality and health risks by using surrogates of certain plasma proteins and smoking exposure-related markers derived from DNA methylation data. Associations with frailty and other aging outcomes have been reported in various cohorts. However, a single GrimAge result does not definitively predict the development of a specific disease or individual lifespan in a person.
What does DunedinPACE attempt to measure?
DunedinPACE is a DNA methylation metric that attempts to estimate the rate of biological change over time, rather than “how old” aging appears. For this reason, it is interpreted differently from a score given in years of age. Its association with physical activity and other lifestyle factors is an active area of research; in a 2026 systematic review and meta-analysis, higher physical activity was generally associated with younger epigenetic age patterns, though heterogeneity among measurements and outcomes was observed.
Does a biological age test determine treatment decisions on its own?
Generally, it should not determine them on its own. Biological age results can provide useful supplementary information in terms of risk communication, monitoring, or research. However, directly modifiable clinical indicators such as blood pressure, HbA1c/glucose, lipid profile, kidney and liver function, body composition, muscle strength, cardiorespiratory capacity, and sleep should also be evaluated concurrently.
Why are functional age measurements important?
In terms of healthy aging, how strong, mobile, and independent an individual is matters just as much as biomarkers. Handgrip strength, gait speed, sit-to-stand performance, VO₂max or appropriate cardiorespiratory tests, and body composition reflect a person’s physiological reserve from different perspectives. Interpreting the biological age panel alongside these measurements provides a more holistic picture.
Can biological age be reversed?
Some studies have reported small changes in certain epigenetic clocks following lifestyle modifications or interventions. For example, in a 2025 DO-HEALTH post-hoc analysis, combinations of omega-3, exercise, and vitamin D were reported to be associated with small changes in certain DNA methylation clocks. Such results are intriguing; however, a clock becoming “younger” by a few months or years does not mean that all organs have rejuvenated to the same extent or that lifespan has been extended by the same amount. Clinically, the more important goal is the real change in risk factors and functional capacity.
Our approach at our Bodrum clinic
We do not base the evaluation of biological age on a single commercial test. If appropriate data are available, clinical PhenoAge can be calculated; alongside this, muscle strength, body composition, cardiometabolic risk, sleep, physical capacity, and, when necessary, selected advanced biomarkers are evaluated together. In serial measurements, the goal is not merely to lower an “age score,” but rather to demonstrate which modifiable health components have genuinely improved.
For the general approach, you can review the Healthy Aging, Biological Age, and Longevity guide, and for the clinical program, the Longevity and Healthy Aging guide.
Frequently asked questions
Which blood tests are required for PhenoAge?
Along with age, albumin, creatinine, glucose, CRP, lymphocyte percentage, MCV, RDW, ALP, and WBC are required. It is important that the units conform to the calculation model.
Is an epigenetic test or PhenoAge better?
They answer different questions. While clinical PhenoAge uses more accessible routine laboratory data, epigenetic clocks evaluate DNA methylation patterns. Which method is more useful may vary depending on the purpose of the evaluation and the follow-up plan.
Is a single biological age test sufficient?
A single measurement can provide a starting point. To evaluate change, serial monitoring using the same method, similar measurement conditions, and a clinically meaningful time interval may be more useful.
References
- Zurbuchen R, et al. Methods for the assessment of biological age – A systematic review. Maturitas. 2025;195:108215. PMID: 39938306.
- Levine ME, et al. An epigenetic biomarker of aging for lifespan and healthspan. Aging. 2018. PMID: 29676998.
- Johnson AA, Shokhirev MN. First-generation versus next-generation epigenetic aging clocks. Biogerontology. 2025. PMID: 40533678.
- Shan J, et al. Physical activity and biological age measured by DNA methylation clocks: a systematic review and meta-analysis. Lancet Healthy Longev. 2026. PMID: 42068988.
- Bischoff-Ferrari HA, et al. Individual and additive effects of vitamin D, omega-3 and exercise on DNA methylation clocks. Nat Aging. 2025. PMID: 39900648.
Written and medically reviewed by: Dr. Kerem Çağlayan
Last medical review: September 10, 2026
Disclaimer: This content is for general health information; biological age tests alone do not replace a diagnosis or treatment decision.
