How is biological age tested?
Many biohackers seek to reduce biological age with various interventions, from caloric restriction to supplements such as NMN. But since the field of longevity is wildely understudied (thanks, pro aging narrative!), how to know what’s working for a particular individual? For you, maybe? Take a look at some of the ways we can measure biological age, it might help you decide what to spend your money on.
First though, let’s make sure we are all on the same page about biological age.
Getting older != aging
Biological age, just like aging, has no official definition. The idea, however, roughly stays the same across papers. If aging is defined as the “lifelong accumulation of damage that occurs as an intrinsic side-effect of the body’s normal operations”, then biological age could be defined as the level of such damage that has occured.
And yes, that means exactly what you might think it means: not all 50 year olds, for example, have the same amount of cellular damage. This might sound surprising, but there is no law of the universe that states that the passage of time must translate into bodily degradation. In other words, getting older != aging.
What you can understand from this is that it’s very possible to control your aging to a significant extent by having a healthy lifestyle.
What are the tests like and are they legitimate?
Biological age tests are done with a third party which is always a scientific company or organization. In order for them to give you your biological age, you need to give them a sample of either blood or saliva, depending on the test. Then, the lab takes it from there. There is very little input needed from you for most tests.
After it’s done, you’ll be given a quantitative result. That is, you won’t simply be told whether you are younger or older than your chronological age: you’ll actually be given a chronological age that corresponds to the level of damage seen in your cells. That is your biological age.
Let’s go through 3 types of biological age tests and their accuracy. There is a TLDR at the bottom of the page.
First, there are online tests based on blood test markers (such as PhenoAge)
This is the type of test that takes into account important biomarkers such as the levels of blood glucose, lymphocyte count and C-reactive protein. With this test, you get all sorts of blood tests done and plug the results in an online calculator. While this admittedly doesn’t sound very reliable, it actually does a pretty good job.
PhenoAge, for example, one such online test, hasn’t been developed just to entertain people on the Internet: it’s actually been created by Morgan Levine, PhD and advisor at Elysium Health, in collaboration with Steve Horvath himself. So, it’s actually not a test to discard. Let’s look into its key characteristics.
Pros as a scientific tool
- Strongly correlated to chronological age (by 94%)
- Holistic approach to aging. This test takes into account immune fonctions, metabolic functions, inflammatory markers as well as the health of 2 key organs: the liver and the kidney
- Recently developed (less than 6 years old)
- Better predictor for the diseases of aging than any previous method
Cons as a scientific tool
- Leaves out epigenetic methylation profile.
- The correlation coefficient isn’t the highest on the market.
***It’s worth noting that although any coefficient might tell us more about people’s lifestyles than it does about the test, it could also indicate our knowledge of what the body “should” score at every age is incomplete. A mix of both perhaps.**
Next, there are telomere length tests
This type of test requires a lab to analyse your DNA directly in order to determine the length of your telomeres. Telomeres are like the protective end caps to our chromosomes and they shorten over time, leading to DNA damage). The longer your telomeres, the younger your likely biological age.
Already, we’re starting to look at the DNA itself, but this doesn’t mean this test is a better choice than PhenoAge. Indeed, while PhenoAge takes into account multiple biomarkers, the telomere-based tests only account for exactly that: the telomeres, which don’t necessarily tell the whole story. Let’s break it down.
Cons as a scientific tool
- Longer telomeres aren’t always better — studies have shown individuals in the 99th percentile of telomere length were more prone to cancers, for example, because more available divisions mean more chances for a cancer-promoting mutation to appear
- Weak correlation to chronological age — a mere 30%
- Incomplete look at aging
Telomere-based biological age tests have been branded as “molecular hand reading” by Mary Armanios from the Telomere Center in the McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins University School of Medicine.
In short, if you’re looking for a way to measure your biological age, telomere length-based tests are NOT the way to go. Those are more pseudoscience than science, at least for now due to the current state of our technology.
Lastly, there are epigenetic alterations tests
This type of test is the most widely used, both in scientific research and for the general public. Because epigenetic alterations are incredibly impactful when it comes to aging (arguably more than telomere shortening), this type of test is considered the most accurate, which is why I you can go with a service that uses an epigenetics-related technology, such as bisulfite sequencing, or array/bead hybridization, which is a subtype of this powerful tech.
And yes, it’s used in research: countless studies on aging require such reliable epigenetics tests to arrive at strong conclusions about the effectiveness of a treatment. Such epigenetic tests are at least part of the reason we know that overexpression of the Yamanaka factors in mice does rejuvenate them, for example, and that’s a pretty exciting discovery.
(The Yamanaka factors are epigenetic reprogramming factors, their overexpression “resets” the epigenome back to a youthful profile.)
So epigenetic alterations are a complex phenomenon we cannot do justice by explaining it here, but in short, it refers to your cells going whack and not knowing what to do anymore. With the epigenetics-based biological age tests, the lab takes a look at the state of your epigenome, looks at which genes are overexpressed and which ones are under-expressed, and thanks to that determines the age it thinks you are. That will be your biological age.
Pros as a scientific tool
- Takes a look at epigenetics, a super important factor for aging.
- The Horvath Clock (developed by the same Steve Horvath from PhenoAge), the most accurate of these types of tests, is correlated to chronological age by 98%, making it, in theory, the most accurate testing means available.
- Recently developed (< than 12 years)
Cons as a scientific tool
- No cons compared to other means of testing.
Conclusion
In conclusion, while no biological age test is perfect, the PhenoAge calculator as well as the Horvath clock are good enough to measure our true age and prove that the concept actually does exist and matter. And while this is totally optional, having your biological age tested with an epigenetic test, can allow you to see your progress and experiment with understudied interventions.
TL;DR
There are three types of biological age tests. They are classified here in order of insightfulness:
Online tests based on blood test markers — — This is the type of test where you are the most involved. You have to get blood tests done to discover your levels of various biomarkers, and then you need to input the results into the phenotypic age calculator, which you can find here: https://www.longevityadvantage.com/mortality-score-and-phenotypic-age-calculator/.
The phenotypic age calculator was developed by PHD Morgan Levine and Steve Horvath himself (we’ll talk about him a bit later). This online test is correlated to biological age by 94%.
Telomere length tests — — This type of test requires the lab to analyse your DNA directly in order to determine the length of your telomeres. Telomeres are like the protective end caps to our chromosomes and they shorten over time, leading to DNA damage (those two are some of the 9 pathways to aging). The longer your telomeres, the younger your biological age. This test is not very correlated with chronological age, however.
Epigenetic alterations tests — — This type of test is the most widely used, both in scientific research and for the general public. Because epigenetic alterations are incredibly impactful when it comes to aging (arguably more than telomere shortening), this type of test is considered the most accurate.
