Biological Age Testing Explained
Your chronological age is fixed, but your biological age is modifiable. Epigenetic clocks and other aging biomarkers offer a window into how fast your body is actually aging.
Key Takeaways
- →Biological age measures how fast your body is aging, independent of your calendar age.
- →Epigenetic clocks (DNA methylation tests) are the most validated method for estimating biological age.
- →Second-generation clocks like GrimAge and DunedinPACE predict mortality and disease risk better than first-generation clocks.
- →Telomere length testing is commercially available but has weaker predictive value than epigenetic clocks.
Two 50-year-olds can have vastly different health trajectories. One may have the cardiovascular system of a 40-year-old; the other may already show signs of age-related decline typically seen at 60. Biological age testing attempts to quantify this difference. The field has advanced rapidly since the first epigenetic clocks were published in 2013, and several commercially available tests now offer consumers access to this data.
What Is Biological Age?
Biological age is a composite estimate of your body's physiological state relative to population norms for your chronological age. It is influenced by genetics, lifestyle, environment, and disease burden. Several methods exist to estimate it, but not all are equally validated.
Epigenetic Clocks: The Gold Standard
Epigenetic clocks analyze DNA methylation patterns — chemical modifications to DNA that change with age. By measuring methylation at hundreds or thousands of specific sites (CpG sites), algorithms can estimate biological age. The key clocks in use today include:
- •Horvath Clock (2013) — The first multi-tissue epigenetic clock, trained on 353 CpG sites. Correlates well with chronological age but is a weaker predictor of mortality than newer clocks.
- •Hannum Clock (2013) — Trained on blood samples, uses 71 CpG sites. Similar limitations to the Horvath clock.
- •GrimAge (2019) — A second-generation clock that incorporates plasma protein surrogates and smoking pack-years. Strongly predicts time-to-death, cardiovascular disease, and cancer (Aging, 2019). Considered one of the most clinically relevant clocks.
- •DunedinPACE (2022) — Measures the pace of aging (how fast you are aging right now) rather than cumulative biological age. Developed from the Dunedin longitudinal birth cohort study. Published in Nature Aging, it is the most responsive to lifestyle interventions.
- •TruAge (TruDiagnostic) — A commercially available test that reports multiple clock outputs including GrimAge and DunedinPACE. Currently the most comprehensive consumer epigenetic test.
DunedinPACE: measuring the speed of aging
Unlike clocks that estimate a single biological age number, DunedinPACE measures your current rate of biological aging. A value of 1.0 means you are aging at the expected rate; below 1.0 means slower. Studies show DunedinPACE responds to caloric restriction, exercise, and other lifestyle changes within months.
Telomere Length Testing
Telomeres are protective caps on the ends of chromosomes that shorten with each cell division. Shorter telomeres have been associated with aging and age-related diseases. However, telomere length has high natural variability, is influenced by the measurement method, and has weaker predictive power for mortality than epigenetic clocks. It is commercially available but generally considered less informative for individual decision-making.
Limitations to keep in mind
Biological age tests are research-grade tools being offered to consumers. Results can vary between tests and between repeat measurements. They are best used to track trends over time rather than to make clinical decisions from a single data point. No biological age test has been validated as a diagnostic tool by the FDA.
What Can You Do With the Results?
The primary value of biological age testing is tracking your rate of aging over time in response to lifestyle changes. Interventions with the strongest evidence for slowing biological aging include regular exercise (both aerobic and resistance training), caloric optimization, quality sleep, stress management, and avoidance of smoking and excessive alcohol. Retesting every 6–12 months allows you to see whether your interventions are having a measurable effect.