Epigenetic clocks are multiplying year by year. Each is a weighted algorithmic combination of the status of various methylation sites on the genome, built by analyzing the epigenome of many different people at different ages in order to arrive at correlations with chronological age, or, more usefully, with metrics such as mortality risk that reflect biological age, the burden of molecular damage and its consequences.
This process of building a new clocks is the easier half of the challenge, however.
The hard part, that still lies ahead, is to determine what exactly it is that these clocks measure.
What do these characteristic epigenetic changes of age actually reflect, in terms of the underlying processes of aging? That is a challenging question to answer well, but answers are needed if epigenetic clocks are to be used to speed up development of rejuvenation therapies by measuring biological age before and after a short treatment.
Source: Fight Aging!