Epigenetic clocks are produced by examining age-related changes in DNA methylation, finding combinations of such changes that are consistent across populations, and predict chronological age. These clocks also predict mortality, in the sense that people with higher epigenetic than chronological age tend to have a higher mortality risk, or be more burdened by chronic age-related disease.
The challenge here is that it remains very unclear as to what these epigenetic clocks are actually measuring, which of the underlying processes of aging they reflect, and to what degree. That makes it hard to use epigenetic clocks in any meaningful way – the results are not actionable.
There are other issues to be debugged as well. For example, that the first generation epigenetic clocks are unaffected by fitness differences, or that they appear to systemically underestimate age in older individuals.
Given that second point, when looking at the results in the paper here, in which slower epigenetic aging is claimed for a cohort of exceptionally long lived individuals, we are left somewhat in the dark regarding the relevance of the data. These and other issues are not insurmountable problems, but they are standing in the way of broader application of epigenetic measures of biological aging.
Source: Fight Aging!