How old are you … physically?

We know that different people age at different rates, so an interesting question to ponder is “How old an Individual is Biologically?”. While you might indeed be, lets say 35, chronological years, have you actually been aging at a faster rate, or even perhaps aging at a slower rate and have the body of a 30-year-old.

To answer such questions efforts have long been underway to find a reliable, effective way to measure physiological age in order to relate that to remaining life expectancy and mortality rate. If you could find a viable biomarker of aging that can be easily measured, then you can start to evaluate future therapies that intervene in the aging process, if you can’t find one, then you have no way of knowing if a particular medical anti-aging technology actually works.

All we have right now is what could be best described as “wait and see”, and that quite obviously takes a very long time (and perhaps also a lot of mice). In the years to come there will be lots of new ideas regarding therapies for extending the human lifespan, but without any real way of actually measuring, you will have to wait a very long time to find out if any of these therapies actually work.

Oh but wait, what about Telomeres? (These are the protective caps at the end of chromosomes. They shorten with cell division, and so are part of the clock which decides when a cell reaches the Hayflicklimit and ceases dividing). The theory is that the older you get, the shorter they become, so could this be a viable biomarker for ageing? A study has been done to answer that, so what did they find?

Well, the details are in a paper that has been just been published in PLoS One and is entitled “Is telomere length a biomarker for aging: cross-sectional evidence from the west of Scotland?

Short answer: No. Here are the details …


The search for biomarkers of aging (BoAs) has been largely unsuccessful to-date and there is widespread skepticism about the prospects of finding any that satisfy the criteria developed by the American Federation of Aging Research. This may be because the criteria are too strict or because a composite measure might be more appropriate. Telomere length has attracted a great deal of attention as a candidate BoA. We investigate whether it meets the criteria to be considered as a single biomarker of aging, and whether it makes a useful contribution to a composite measure.


Using data from a large population based study, we show that telomere length is associated with age, with several measures of physical and cognitive functioning that are related to normal aging, and with three measures of overall health. In the majority of cases, telomere length adds predictive power to that of age, although it was not nearly as good a predictor overall. We used principal components analysis to form two composites from the measures of functioning, one including telomere length and the other not including it. These composite BoAs were better predictors of the health outcomes than chronological age. There was little difference between the two composites.


Telomere length does not satisfy the strict criteria for a BoA, but does add predictive power to that of chronological age. Equivocal results from previous studies might be due to lack of power or the choice of measures examined together with a focus on single biomarkers. Composite biomarkers of aging have the potential to outperform age and should be considered for future research in this area.

Is this the end of the idea that telomere length can act as a BoA? Not at all, another recent paper suggests that more sophisticated measures of telomere dynamics, such as counting changes in the proportion of very short telomeres, are in fact good biomarkers of aging, that however was in mice. The quick summary there is …

  • Mouse telomeres shorten ∼100 times faster than human telomeres
  • The increase in the percentage of short telomeres predicts individual mouse longevity

So basically they suggest that longitudinal telomere length studies are necessary to predict mammalian longevity, so this idea that telomere length can act as a BoA may yet pan out.

“I don’t want to achieve immortality through my work… I want to achieve it through not dying”.  – Woody Allen

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