The passage of time is an irreversible process. However, ever since the dawn of modern science and medical research, efforts have been made to intervene with time and its effects on human health, one of which is aging.
Still, to precisely determine the effect of aging on humans, scientists need to know how old a person is. Unfortunately, the number designated to be your legal age sometimes does not reflect the span of your existence without error.
Therefore, a new term has emerged to describe aging at a cellular level. This measurement is more accurate than the chronological age we have been using and offers various applications in diagnosing and preventing diseases.
This article discusses the differences between biological and chronological age, the factors that get “under the skin” and affect your well-being from within, and how you can determine your health by calculating your biological age.
Biological Age Vs. Chronological Age: How the Years of Your Life May Not Reflect Your Health
Biological Age Vs. Chronological Age: How Do We Define Them?
Biological Age
Biological age is a newly discovered aging biomarker that focuses on the functional capability of a person rather than the years of their existence. The purpose of this parameter is to precisely determine one’s actual physical condition without consideration for the legal age to predict any possible pathology and prevent significant deterioration due to aging.
According to research, biological age as an aging biomarker is defined as “a biological parameter of an organism that will, in the absence of disease, better predict functional capability at some late age than chronological age.”
The same research also states that biological age can predict the rate of aging. In other words, it can tell exactly where a person is in their total life span. Therefore, it is a better predictor of life span than chronological age.
It is worth emphasizing that biological age excludes the effects of diseases, meaning that if an illness shortens a person’s life span, it will not be considered biological age anymore. This parameter must also be acquired without harming the tested person—for example, a blood test or an imaging protocol.
However, it is challenging to establish such a biological marker since aging and diseases are inseparable. Even when the illness is not detected, its effects may still appear at other stages of life. Moreover, the pace of biological aging can vary among different tissues, so it may not be practical to assume a single measurement for the entire lifespan.
Chronological Age
Due to numerous challenges in defining biological age and putting it into practice, chronological age has still been the primary parameter we use for various purposes, including diagnosing one’s physiology and predicting possible diseases.
Chronological age refers to the years of life a person has existed. Unlike biological age, this type of age cannot anticipate a person’s total life span; instead, it calculates how much time a person has lived based on their date of birth.
For this reason, chronological age does not have as many medical applications as biological age. Instead, it is mainly used for legal purposes, such as deciding whether a person may legally engage in a specific activity.
What Are the Factors That Affect Biological Age?
Another noticeable difference between biological and chronological age is that while the latter is fixed, the former is changeable. Biological age can either be higher or lower than your legal age, depending on the following factors:
Nutrition and Diet
According to a study on nutrition and biological age, a high-nutrient diet may help humans age more slowly.
Researchers examined how much people cared about nutrition data when choosing foods. Their biological age is lower (meaning a person is younger biologically) as more attention is given to it. However, when selecting foods beneficial for aging, the result is upsetting: only 12.8% of men and 27.5% of women gave nutrition data some consideration.
Lifestyle Habits
A healthy lifestyle that includes sufficient physical activity and sleep may also help lower the rate of aging.
According to a study, scientists found that people who trained with aerobic exercise had a physiology that was 5.43 years younger than those with a sedentary lifestyle. This result is discovered using an ultra-predictive aging clock composed of nearly 500 protein entries.
Meanwhile, sleep affects aging and relevant health outcomes. For example, a study on the role of sleep in aging found that an increase in sleep quality was associated with a decrease in biological age acceleration. Nevertheless, a limitation of the study is that it only elucidated sleep’s effects on aging due to air pollution and not other causes.
Smoking is another detrimental habit that affects your aging process. For example, a study on smoking and early biological aging found that smokers aged up to two times faster than nonsmokers. Fortunately, another study on smoking cessation found that giving up on this bad habit can reverse its harmful effects on accelerated aging.
Stress and Environments
If you are dealing with a hurtful amount of psychological or physical stress, you are one step closer to reaching the terminal of your total life span.
A study on stress and biological age found that suffering from tension, in any form or quantity, may result in a rapid increase in biological age. Nonetheless, the effects can be reversible after recovery. Furthermore, the study claims biological age is variable and exhibits rapid changes in both directions (for better or worse).
The final factor is the environment. Research shows that harmful environmental chemicals can speed up the rate of aging. Notably, a polluted environment affects aging independently and jointly by decreasing sleep quality, a driver of aging, as mentioned earlier.
How Can We Compare Biological Age and Chronological Age?
Epigenetic Clock
A measure based on DNA methylation, known as the epigenetic clock, is a reliable indicator of biological age. Two of these clock measures, the Horvath and Hannum calculators, are among the most consistent predictors of biological age.
Their validation studies display strong age correlations (0.96 for Horvath and 0.91 for Hannum) and minimal deviations from chronological age (3.6 and 4.9 years). Additionally, both algorithms used large samples (8000 for Horvath and 656 for Hannum) representing various demographics and the complete adult life span.
The Hannum clock works best with whole blood samples and only uses 71 CpG sites (parts of the DNA). In contrast, the Horvath clock is a multi-tissue predictor based on methylation levels of 353 CpG sites. Both predictors share only six CpG sites in common, although the CpG sites were chosen using a similar methodology.
Telomere Length
Every time a cell divides, the DNA sequences that cap the chromosomes, known as telomeres, become shorter. And because shorter telomeres are associated with aging, telomere length is another indicator of biological aging.
Women often had longer telomeres than men, according to a meta-analysis of 36,230 participants and the most extensive population-based telomere length study to date (n = 105,539). As a result, women tend to be biologically younger than men, in line with previous measurements based on DNA methylation.
Telomere shortening is linked to accelerated aging and positively correlates with age-related diseases. The correlation between short telomeres, increased mortality risks, and higher biological age has been demonstrated in numerous studies, most recently in a large study with nearly 65,000 samples.
The study found that telomere length appears to be effective for predicting cancer and cardiovascular diseases, and the effect is independent of the epigenetic clock. Furthermore, a meta-analysis of over 40,000 participants concluded that telomere length can be a risk factor for heart disease after finding 8400 events.
Largest Differences Between Biological Age and Chronological Age
Given that the technology for determining biological age remains in its infancy stage, only a few people undergo a well-established test that provides accurate results. Instead, many find out about their biological age through a superficial prognosis that appears unreliable.
However, there is a widespread consensus among the scientific community that most people have their biological age within five years of their actual age. Others make genuine efforts to put time on their side. Some people may be a decade younger than that due to some reasons, such as having good genes or a healthy lifestyle.
Calculating Your Biological Age
There has only been a minor scientific achievement in establishing a simple way to calculate biological age until now. It requires a complicated protocol, not to mention only professionals in this field can interpret the results of such tests.
At least one well-established biological age test called the Index is available now. This test kit is developed in collaboration with Yale University to provide scientists and the general public with a reliable and precise way to determine a person’s actual age.
As a saliva test, the Index utilizes epigenetics technology. It analyzes a person’s epigenome by examining more than 100,000 sites on the DNA with superior accuracy to measure how quickly a human body is aging and better understand the personal aging process.
However, one restriction of the Index test is the difficulty in interpreting the results, which appears impractical among general users. Also, the result needs to explain how the user can take advantage of their age in developing a strategy to improve it.
So, your healthcare provider is your best option since they can interpret the test results for you and suggest ways to improve your biological age and general health.
Bottom Line
Understanding the biological age is a privilege for delaying accelerated aging and protecting your well-being. Yet, even if you can tell your biological age, it is still vital to stay alert to any possible events that may affect it in the future.
All in all, implementing a healthy lifestyle and a high-nutrient diet is key to maintaining youth and achieving longevity, regardless of knowing your biological age or not.
References
Horvath, S. (2013). DNA Methylation Age of Human Tissues and Cell Types. Genome Biology.
Hannum, G. et al. (2013). Genome-wide Methylation Profiles Reveal Quantitative Views of Human Aging Rates. Molecular Cell.
Gardner, M. et al. (2013). Gender and Telomere Length: Systematic Review and Meta-analysis. Experimental Gerontology.
Haycock, P. (2014). Leukocyte Telomere Length and Risk of Cardiovascular Disease: Systematic Review and Meta-analysis. BMJ.
Lapham, K. et al. (2015). Automated Assay of Telomere Length Measurement and Informatics for 100,000 Subjects in the Genetic Epidemiology Research on Adult Health and Aging (GERA) Cohort. Genetics.
Rode, L. et al. (2015). Peripheral Blood Leukocyte Telomere Length and Mortality Among 64,637 Individuals From the General Population. Journal of the National Cancer Institute.
Jylhävä, J. et al. (2017). Biological Age Predictors. EBioMedicine.
Lei, M. et al. (2017). A Pilot Investigation of the Impact of Smoking Cessation on Biological Age. The American Journal on Addictions.
Han, K. et al. (2018). Biological Age is Associated With the Active Use of Nutrition Data. International Journal of Environmental Research and Public Health.
Skjodt, N. et al. (2018). Smoking Causes Early Biological Aging: A Deep Neural Network Analysis of Common Blood Test Results. European Respiratory Journal.
Lehallier, B. et al. (2020). Data Mining of Human Plasma Proteins Generates a Multitude of Highly Predictive Aging Clocks That Reflect Different Aspects of Aging. Anatomical Society.
Poganik, J. et al. (2022). Biological Age is Increased by Stress and Restored Upon Recovery. Cold Spring Harbor Laboratory.
Gao, X. et al. (2022). Role of Sleep Quality in the Acceleration of Biological Aging and Its Potential for Preventive Interaction on Air Pollution Insults. Anatomical Society.
If you have questions about biological age vs. chronological age or any health problems discussed here, connect with us and learn more.
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