concept

Epigenetic clock

A way of measuring biological age by reading DNA methylation levels at hundreds of specific sites across the genome. These sites shift regularly enough with age that a statistical model can predict a person's age from a blood or tissue sample, sometimes to within a few years. Second-generation clocks also correlate with disease risk and mortality, not merely with years lived. But these are statistical biomarkers, not clinical evidence: regulators do not recognise "aging" as a treatable disease, so an intervention seeking approval must still show a reduction in concrete events such as stroke or frailty. Slowing the clock on paper is not the same as someone living longer.