DNA-Methylation Age
Your birthday says 35. Your DNA might be quietly running you at 41.
Grounded in the research on epigenetic clock
So what is it actually measuring?
Not your birthday. Your cells stick chemical tags called methyl groups onto specific spots on your DNA, and the pattern shifts in a predictable way as you age. Read the methylation at the right spots and you can guess someone's age without ever asking. That guess is your DNA-methylation age, aka biological age. The tags change with how you've actually lived, not just how long.
Who came up with this?
Steve Horvath, a UCLA geneticist, in a 2013 Genome Biology paper. He trained an algorithm on 51 tissue types and found 353 specific CpG sites whose methylation predicts age across basically the whole body, blood, brain, liver, all of it. Correlation with real age around 0.96, error about 3.6 years. Gregory Hannum dropped a blood-only 71-site clock the same year. Horvath's was the first true multi-tissue one.