Epigenetic clocks do not mirror functional aging or mortality risk, with most epigenetic changes occurring during development and slowing after age 80.

“So, it's not stable but it actually doesn't mirror what we think of in terms of functional aging. So, if you think of a frailty index or even mortality risk, it increases exponentially after, let's say, age 30. The epigenetic clocks show a totally different pattern, it's still not linear but actually most of the changes happen during development. So, you have this huge increase in epigenetic age between...we can even measure it in fetal samples...and then it kind of starts becoming more linear and steady around age 20 and then, interestingly, actually slows down again, you know, very late, so, after, let's say, age 80.”