Can an epigenetic age test really tell you how old your body is?
An epigenetic age test provides a meaningful indication of biological ageing, but is not yet a definitive verdict on your health. Use the result as a starting point for a conversation with your doctor, not as a fixed judgement.
Horvath's epigenetic clock was validated on more than 8,000 tissue samples from 51 different healthy tissues and cell types. Newer clocks followed, such as PhenoAge and GrimAge. PhenoAge outperforms earlier versions at predicting mortality, cancer, cognitive disease, and physical functioning. Cancer tissue showed an average of 36 years more epigenetic ageing than healthy tissue from the same person, illustrating how large the deviation can be.
People whose epigenetic age comes out higher than their calendar age have an increased risk of mortality, cardiovascular disease, cancer, and diabetes. That association has been found consistently across multiple clock types, although the size of the effect varies by clock. How large your risk actually is therefore depends on which clock is used and how it was measured. Factors such as high body weight, HIV infection, and male sex are associated with an accelerated biological age on at least one of the clocks.
There are, however, serious limitations. The clocks have not yet been well validated in large-scale studies that follow people over a long period of time. There are also technical challenges: mixed cell types in a blood sample, for instance, can influence the outcome, which makes interpretation difficult. Causal relationships have moreover not yet been demonstrated; the associations found are just that, associations. You cannot simply conclude that lowering your epigenetic age will make you live longer.
Lifestyle, diet, genetics, and disease all influence the measurement. This means the test is sensitive to what is happening in your life, which is both an advantage and a disadvantage. An advantage because interventions can in principle be made visible; a disadvantage because day-to-day fluctuations can colour the outcome without anything genuinely changing in your health. These clocks are increasingly being used as an evaluation tool for anti-ageing treatments, but the methods for doing so are still very much under development.
Claims are based on seven sources, including a systematic review of 156 publications and multiple validation studies. All associations are associative in nature; no RCT evidence for causality is available.