In the early 2010s, a series of studies, first and most notably by Steve Horvath, PhD at UCLA, has shown that the pattern of DNA methylation (DNAm) changes in a very predictable fashion with age. About 60% of the time these CpGs acquire less methylation with age and 40% of the time they acquire more methylation. The pattern is so tightly correlated with chronological age that it has been heralded as the most powerful biomarker of aging predicting chronological age with an accuracy of about +/- 2 years. While other composite biomarkers of aging can predict chronological age with up to 70-80% accuracy (+/- 5 years), these DNAm Age clocks can do so with up to 96-98% accuracy. In addition to functioning as biological clocks, more recent studies have shown that different DNAm Age methylation patterns can predict a host of chronic diseases of aging and time to death in large cohorts of subjects.
