A cell's finite capacity to divide – a phenomenon known as replicative senescence – is an intrinsic feature of the body's cells and fundamental to the aging process. Telomeres in most human cells shorten during aging, suggesting that it is both a cause and a biomarker of aging. In this clip, Dr. Elissa Epel explains how new research using Mendelian randomization techniques is providing insights into the dual nature of telomeres.

Rhonda: In your experience, how much would you say that telomere length...so, you know, the telomeres get shorter with time and shorter telomeres are supposed to correspond to aging. How much would you say that telomere length regulates the aging process, like actually plays an active role, versus just is a biomarker, something that is just biomarking the aging process?

Elissa: That's a good question. So telomeres are one specific pathway of how a cell ages, and how our tissue ages. And the pathway is this, it's called replicative senescence and it's basically how long can that cell continue to divide, and divide, and replenish into new fresh young cells. So the telomeres, when they get too short, prevent that particular cell, whether it's an immune cell or a neuron in our hippocampus or the lining of our cardiovascular system, we need those cells to replenish throughout the decades. When it to the telomeres gets too short that cell stops dividing. And so it's basically a little window into how long can these cells continue dividing. If the telomeres are long, they have a long potential for replenishing tissue.

Elissa: One last point about genetics. So you were you earlier asked, like, is this a marker of aging or is it a mechanism? So it is probably both. And the way we know that it's the mechanism as well is... I mean, partly the example to some of these genetic disorders, but even more so, now we know that if you have a genetic propensity for long telomeres, it directly predicts less heart disease and dementia. So that was those kinds of Mendelian randomization studies are one of the best ways that we can say there's a direct physiological connection here.

Rhonda: Right yeah, I didn't know there were any Mendelian randomization studies on it. That is very interesting. So cardiovascular disease and dementia are two one's health outcomes that seem to be effective.

Elissa: Right. And then as I said the higher cancer risk for some of these.