Age is Just a Number?

Do you know anyone who's celebrated their 29th birthday for the 40th time? Or have heard the phrase "You are only as old as you feel"? Well, is there any truth to that?

In an effort to understand and predict aging, scientists, epidemiologists, and actuaries have developed several different measures of aging, with varying degrees of reliability. We will take a look at many of the common measurements of age, in alphabetical order.

Actuarial Age

Actuaries in the life insurance field use mortality tables, statistical summaries of death rates for a population, as the basis for their predictions. But if you die in between your 87th and 88th birthday, should you be counted as an 87 year old or an 88 year old? Those clever actuaries can recognize either and will consider your Age Nearest Birthday or Age Last Birthday as their measurement basis.

Biological Age

A catch all term that indicates that a person's body has information in it that tells us how close we are to an expiration date. Biomarkers are the sources of this information, and we will learn about some of them that are used as "clocks" in this article.

Biomarkers can be found in blood, saliva, urine, and more. Many are related to a key organ or system. You may have a young heart but an old liver, for instance.

Several health and fitness companies will develop their own special sauce, blending different combinations of markers as part of their claim to determine your "real" age.

Bryan Johnson is taking this to the extreme, attempting to achieve "optimal" targets on hundreds of markers. His "Blueprint" is rather extreme, and expensive, but he publishes all his measurements online.

Chronological Age

Happy Birthday to you! This is the number everyone is most used to, the number of solar orbits you've made since you went from in utero to an 'independent' being.

Although, in traditional eastern cultures, everyone gets a year older on the lunar new year.

And if you are born on a leap day, well, just consider yourself lucky!

You don't have to measure in years though, between age 27 and 28 you can celebrate your 10,000th day of life. Or maybe measure in "seasons of love?"

Cognitive Age

There are two instances of 'cognitive age' in the literature.

The first is self-rated. Imagine you never knew when you were born, and you owned no watches or calendars. How old would you say you are? This is your 'cognitive age' which doesn't really have anything to do with how well your brain works, but is more of a perception measurement.

The second is determined by how much cognitive decline a person has. This can be measured through questionnaires, neurological markers, and brain mass.

Epigenetic Age via DNA Methylation Clocks

Your DNA is a wonderful set of code. Many genes can be expressed in different way based on a variety of external influences.

In particular, special compounds called methyl groups accumulate as a part of the aging process and effect genetic expression.

Measuring the types and quantities of these substances across the body can be a way to estimate biological age. The "Horvath Clock" is one of the earliest and most well known.

Facial Age

In today's world of biometric scanning, the map of your face can carry a lot of information. Using an extensive training dataset, an algorithm can predict your actual age and perceived age based on the lines and shapes of your face.

Insurance underwriters may use this data to detect evidence of tobacco use.

An interesting comparison may be to pit the computers against the world's best carnival guessers.

Functional/Fitness Age

In this sort of metric, you perform sort of test and see how that stacks up against a population average at each level. This can be on a singular dimension, such as your VO2 max (how much oxygen your body can use during exercise) or resting heart rate, or some combination of assessments.

Muscle and bone density can be additional metrics, along with range of motion or flexibility data.

Glycan Age

Glycans are not an alien race from Star Trek. Throughout the human body you can find proteins, sugars, lipids and other building blocks that are important to bodily function and cellular structure.

Glycans are among these substances. They are important for metabolism and immune responses.

They can be monitored and measured and when they show signs of deterioration, it may be an indication more inflammation which can contribute to aging.

Heartbeat Age

Across mammals, species tend to have about the same number of ticks, approximately 1 billion heartbeats) they just use them at different rates. This is partially the basis of "dog years".

Reproductive Age

Reproduction is a huge factor for human growth, development and aging. Particularly in women, onset of puberty, peak fertility and menopause are key milestones in life. In past articles, we've discussed why post reproductive longevity is a special and unique thing for humans. But in the context of this article, the fact that there is a finite number of eggs that dwindle over time could be a way to measure progress along the pre-menopausal life curve for females. Many factors can contribute to variation in this path, from ethnicity, to environment, to use of contraceptives.

For men, sperm count and quality can be measured, but they tend to follow similar patterns of cellular aging.

Survey Based Age

One of the most popular online quizzes is the Real Age Quiz. Over 45 million people have answered 150 questions about their health in order to get an estimate of their actual age.

Surveys are nice because they don't require any lab work, but that also is a potential flaw. Subjective, self-reported health assessments can be flawed. And it may be that these evaluations are more of a marketing tool than anything else.

Telomere Age

One of the earliest DNA based measurements of longevity was the Telomere. This little tail on the end of a DNA strand gets shorter as a result of cellular division. When it gets short enough, cells stop dividing (senescence), which could be a contributing factor to aging.

Flipping The Script

Instead of trying to figure out how far you've come, perhaps a more important consideration is to try to figure out how much time you've got left.

Many financial advisors and retirement organizations may promote a LONGEVITY Calculator.

Recently, the Society of Actuaries and Academy of Actuaries updated their version of the Longevity Illustrator to help individuals prepare for retirement.

Caveats and Considerations

Question 1: Can I fix it?

Suppose two people buy the same car, but one lives in the northern US, and one lives in the south. The northerner drives to work everyday, and the southerner only takes the car out once a week to buy groceries. Ten years later, the northern car would seem "older" (more rust, worn tires, more miles driven) even though the same amount of time has passed.

A tricky question for these biomarkers and measurements is whether they cause aging or are caused by aging. A way that this can be evaluated is by considering what would happen if the clocks were "reset".

Using our car analogy, resetting the odometer to zero wouldn't affect the car's useful life at all, and fixing all the rust could make the car look younger, but the engine is still well aged. Now suppose we discovered a regenerative technology that allows the engine to repair any damage it incurred after every trip. Our car would be perpetually young.

As of this writing, reversing these aging mechanisms is still not something that can be done. We can slow some, and replace certain body parts, but for the now the best we can do is continue to sleep well, exercise, and eat nutritiously.

Question 2: Is it worth it?

Another consideration is how easy or expensive it is to do these measurements. Looking at genetics requires lab work and computation. Monitoring someone's respiration rate is less technical and more accessible.

For researchers and insurers, it may be worth investing in more data points. However, an average consumer may not be willing to shell out a few hundred bucks to perform an assessment.

Finally, once we have these numbers, how easy are they to change? Does it require a pharmaceutical or surgical intervention? If you do all the "right" things with respect to diet, rest, movement and connection, would you be able to move the dial in a significant way? And does constant monitoring of all these things actually create more stress and anxiety?

Question 3: Are they reliable?

For researchers trying to predict morbidity and mortality, the answer may be a qualified yes, depending on the type of measurement.

For the consumer, it is important to look at the margin of error of these estimates. You may be concerned if your biological age comes out 5 years older than your chronological age, but if the estimate has a +/-7 year range, you could be just fine.

Like credit scores, different groups will have different measurements, and many of the algorithms are behind the curtain. How do you reconcile having a dozen different ages with some younger and some older than your birth age?

And if you are a healthy 74 year old and your biological age comes out to 50, does that imply you have 70 more years of life? Probably not.

In, the end, maybe these are decent gauges of your current health, or maybe they are just a form of entertainment.

Question 4: Who is using my data?

In the age of the internet of things, your doctor, your insurance company and the drug and wellness industries may view you as super data generator. From Fitbits, to Oura rings, to Nuerolink, to the latest Apple Vision Pro, continual data collection will continue to grow. Who uses this data how will continue to unfold in the next few years.

Regardless of how you measure it, or if you measure it all, we all will age and our time on this planet is unknown. Longevity Assistant can help you manage those precious moments in ways that hopefully give you a bit more time, or allow you to make the most of the time you have.

Further Information

For an even deeper exploration of this topic, there is a fantastic Biological Age Diagnostics Report by the Longevity.Technology website.