# Hannum clock

The Hannum clock is a blood-based epigenetic age estimator, published by Gregory Hannum and colleagues in 2013. It uses DNA-methylation levels at 71 CpG sites, taken from whole-blood samples of 656 people, to predict your chronological age. It does so with a cross-validated correlation of about 0.96. Unlike the multi-tissue Horvath clock, the Hannum clock was trained and validated specifically in blood. That makes it less generalizable to other tissues. It is still widely cited. But for predicting death, it has largely been overtaken by second-generation clocks, which were trained on health outcomes.

## Sources

- Hannum G, Guinney J, Zhao L, Zhang L, Hughes G, Sadda S, Klotzle B, Bibikova M, Fan JB, Gao Y, Deconde R, Chen M, Rajapakse I, Friend S, Ideker T, Zhang K. (2013). Genome-wide Methylation Profiles Reveal Quantitative Views of Human Aging Rates. Molecular Cell. https://doi.org/10.1016/j.molcel.2012.10.016

---

_Canonical: https://longevity-switzerland.com/en/glossary/hannum-clock · Part of Longevity Cities · Updated 2026-06-22_