Longevity & AgingMost Epigenetic Clocks Are Technically Reliable But Biologically Unstable
Epigenetic clocks are popular tools for estimating biological age from blood DNA, but a new Yale study exposes a critical flaw: while most clocks reproduce well across laboratory replicates, they fluctuate significantly in response to ordinary events like eating a meal, experiencing stress, or changing altitude. Researchers tested 18 DNA methylation biomarkers across seven datasets and found biological reliability was substantially lower than technical reliability — and the two did not predict each other. PC-based clocks, especially PCGrimAge and SystemsAge, performed best overall. Crucially, clocks with low biological reliability produced inconsistent disease predictions and misleading intervention results, undermining their use in clinical trials and personalized medicine.
