To reflect overall aging, you need to measure a range of factors from many systems, including physical and mental factors that will vary with age. What is termed your “biological age” is the sum of these factors. It compares all your body’s functions with those of your peers. The idea has merit because it should identify those who are “young for their age”, or “old for their age”.

Health and aging

Assessment of your biological age includes detection of risk factors and early signs of disease as predictors of premature mortality. However, aging is far more than the absence or presence of disease. Equally, there are many factors that predict lifespan that have nothing to do with the aging process. Nonetheless, practitioners have traditionally looked to signs of disease as the most convenient way to measure biological age. This is mostly because lifespan is determined by the time it takes to die (usually of some disease).

Certainly, disease prevention is a key component of any strategy to slow aging but, while the presence of disease potentially compromises longevity, its absence does not guarantee it. In aiming to stay healthy and increase your healthspan, you need to estimate how well you really are as well as how sick you might be.

Biological age is also not the same thing as health status, though of course the healthier you are, the more likely you are to be biologically younger relative to (unhealthy) others.

Measuring the causes

Measurements of some of the mediators or causes of aging are often used to determine your age, as more active aging usually implies an older biological age. For example, measures of oxidative stress, inflammation, glycation, stress and hormone levels are all important determinants of many age-related changes and are consequently used by some practitioners as a means to judge you as older or younger than your chronological age.

These kinds of tests can be handy, as the results can be directly modified by interventions that you can choose, giving a sense that aging is also being modified. While this may very well be true, there’s a number of limitations that make extrapolation of age from a single blood or urine test problematic.

• For many tests there are no age-standardised reference ranges to know that you are more or less than your peers; to know if your level is high or low for you and impacts on your health today and in the future. Even if there is a normal range, “normal” simply means you are functioning at the same level as your peers and every test has a normal range.
• Aging is the sum of a number of processes. Consequently, any assessment, as well as any intervention strategy, must reflect and address of range of processes. Single measures of any one thing fail to accurately reflect changes in the whole.

In general, the more comprehensive the choice and assessment of parameters in all the important regulatory systems, the better their ability to predict the cumulative effects of aging and, ultimately, its outcomes.