Telomere length has been claimed as a predictor of lifespan, but how direct is the correlation between telomere length and longevity? What can we really determine about how long someone is likely to live, based on telomere length?
One study which delves into this issue measured the telomere length of Zebra Finches from nesting age throughout their natural lifespan (between 1-9 years) to determine if there was a correlation between telomere length at an early age and lifespan.
As it turns out, as found by Heidinger et al. in the study Telomere Length in Early Life Predicts Lifespan, Zebra Finches whose telomeres were twice as long at nesting age on average lived 50% longer lives. Telomere length was thus shown to be a strong predictor of lifespan, with a P value of < 0.001, indicating a very strong likelihood for correlation.
The question, then, is how does this relate to humans? Unfortunately, it is a bit more complicated to obtain such data for people, because our lifespans are, on average, fairly long, and the technology to measure telomere length has not even been around for the life of a generation.
However, we can look to Cawthon et al.’s study Association between telomere length in blood and mortality in people aged 60 years or older to confirm that there are certainly dynamics between telomere length and longevity in humans as well. The study found a statistically significant (but less so than in the finches) P value of 0.004 between telomere length and lifespan.
The simplest explanation (and according to the principle of Occam’s razor, the most likely) is that the finches were all placed in the same environment, taking lifestyle out of the equation. With humans, this is impossible, thus the dynamics between telomere length and longevity are not as direct.