Steve: the epigenetic clock is actually very much under genetic control. Some people just inherit a genome that makes...or DNA that really allows the epigenetic clock to progress more slowly. And so, the heritability is about 40%, you know. So, in this sense, it's not just lifestyle factors.

Rhonda: I recall from your looking at the epigenetic clock of the semi-supercentenarians, people that are like 105 years old, they had epigenetic aging clocks that were like 8.6 years younger than their actual chronological age.

Steve: Yeah. That's true. It's true. That's a manifestation of that so, if you have a parent who lived until age 100 or 105, then chances are that your blood is actually younger than the blood of a person of the same age, same gender, same everything, but whose parents didn't live until age 100, you know. So, the offspring of centenarians obviously have a genetic advantage, hopefully, but also that is manifested in the epigenetic clock.

Rhonda: Yeah. So, you see that their epigenetic aging seems to be slower.

Steve: Yes. So, that's one line of evidence, but there's another. So, people have these longitudinal epidemiological studies, and they may have collected a blood sample from a person when they were, let's say 40 years old, and then 15 years later, they get a second blood sample. And so, you can then ask the question whether a person who was aging quickly at the first blood draw, did they still age quickly at the second blood draw? And the answer is yes. And conversely, you observe the same for people who age more slowly, you know. And, in my opinion, this could already be observed when you study, let's say a person at a young age, age 20. Draw their blood, then if you follow them for 60 years, you know, you would find this consistency that people who are slow agers at age 20, they are also slow agers at age 60 or 80. So, if you analyze the blood from a centenarian or supercentenarian, it's true, our age estimates are really way below the chronologic ages, could be 15 years younger, and also there's a real leveling-off effect, you know.