What you've heard
An epigenetic age test tells you how fast you are aging
Verdict
Not reliable for individuals
Can an epigenetic age test tell you how fast you are aging?
Not reliable for individuals.
Cells tag their DNA with small chemical marks, and the tags at a few hundred sites predict a person's age across almost every tissue. These "clocks" work well for comparing large groups. For one person, they wobble: run the same sample twice and standard clocks could disagree by up to nine years from technical noise alone. In a two-year calorie-restriction trial, the best human evidence that a clock can be moved on purpose, one clock of three slowed slightly and the other two did not move. The best-known number about telomeres, the protective caps on chromosomes, has the same problem: the claim that stress added nine to seventeen years of cellular aging was an extrapolation from mothers measured once each.37 A test that cannot agree with itself cannot tell you whether last month's habits worked.
Where the book tests it
What the book recommends instead
Keep your strength and grip
StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.for strengthProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.for longer lifeHow: twice a week, about half an hour: sit-to-stands from a dining chair (a cushion raises the seat if your knee complains), push-ups against a wall or counter, rows with a band, and a heavy shopping bag carried in each hand (Chapters 1 and 4). Once or twice a year, count how many times you can stand up from a chair in thirty seconds without using your hands, and write it down; treat a poor score as a reason to train rather than a forecast. Why: strength falls faster than muscle bulk with age, and weakness predicts disability and earlier death.
Sources
- 37.Horvath, S. (2013). "DNA methylation age of human tissues and cell types." Genome Biology, 14(10), R115. https://doi.org/10.1186/gb-2013-14-10-r115; Higgins-Chen, A.T., Thrush, K.L., Wang, Y., Minteer, C.J., et al. (2022). "A computational solution for bolstering reliability of epigenetic clocks: implications for clinical trials and longitudinal tracking." Nature Aging, 2(7), 644-661. https://doi.org/10.1038/s43587-022-00248-2; Waziry, R., Ryan, C.P., Corcoran, D.L., Huffman, K.M., et al. (2023). "Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial." Nature Aging, 3(3), 248-257. https://doi.org/10.1038/s43587-022-00357-y; Epel, E.S., Blackburn, E.H., Lin, J., Dhabhar, F.S., et al. (2004). "Accelerated telomere shortening in response to life stress." Proceedings of the National Academy of Sciences, 101(49), 17312-17315. https://doi.org/10.1073/pnas.0407162101 (CALERIE: DunedinPACE slowed about 2-3%, PhenoAge and GrimAge unchanged.)
Note numbers are those of Chapter 16, Aging Well.
This verdict is one of the "What you've heard" boxes in Chapter 16, Aging Well, where the book tests the claims people repeat against the studies behind them.
Educational content, not medical advice. Disclaimer.