Biological Age Tests Are Measuring Something. It Isn't Your Age.

Epigenetic clocks have poor test-retest reliability and no validated response to intervention. Here is what to track instead.

Epigenetic clocks estimate age from DNA methylation patterns, and the better ones — the second-generation clocks trained on mortality and morbidity rather than chronological age — do carry real population-level information about risk. That is a different claim from the one the consumer market makes.

The reliability problem is decisive for personal tracking. Split a single blood sample and send both halves to the same provider and the two results can differ by several years. Any 'improvement' smaller than that spread is noise, and almost every marketed before-and-after is smaller than that spread.

There is also no clock that has been validated as an intervention endpoint. No trial has shown that lowering a clock reading lowers actual disease incidence, which means the number cannot yet function as a target.

What to track instead, quarterly or annually: ApoB, fasting insulin and HbA1c, blood pressure, VO2 max or a submaximal proxy, grip strength, and waist circumference. Each has direct outcome data, each responds to intervention within months, and together they cost less than one epigenetic panel.

Editorial note: this article summarises published research for general information. It is not medical advice. Discuss any intervention with a qualified clinician.