Chronological vs. Biological Age

Understanding the Differences and Factors That Affect Your Health

Your chronological age and biological age might not be the same. Chronological age is the number of years you've been alive, while biological age refers to how old your cells and tissues are based on physiological evidence.

If you're especially healthy and fit for your age, your biological age may well be lower than your chronological age. But if you're sedentary, chronically ill, or in poor physical condition, your biological age may be higher.

Research suggests that biological age is more accurate than chronological age for predicting the onset of disease and death.

This article looks at chronological versus biological aging, how biological age is determined, and how you may be able to lower your biological age.

Older men sitting on stone wall in park
Cultura RM Exclusive / yellowdog / Getty Images

Chronological vs. Biological Age

Your chronological age is unchangeable. You were born on a particular day and have spent a certain amount of time on the planet. As much as some people may want to change that, you can't.

However, you've likely met a few people whose chronological age surprised you because they looked or "seemed" much older or younger than their chronological age. Their biological age may be significantly different from the chronological measure.

Much of how you age is influenced by genetics and beyond your control. But research shows aging can be impacted by external factors, including:

  • Diet
  • Exercise
  • Stress
  • Smoking
  • Sleeping habits
  • Physical environment (where you live, work, etc.)

Biological age, also called physiological age, is affected by these things and more, and experts say the state of your DNA (genetic material) is a reflection of all those factors.

Because biological age may predict things like whether you'll develop diabetes or dementia, or how soon you'll die, it may someday become the more important number on your medical chart.

Also, you likely have some control over your biological aging and can even get "younger" by making positive changes. Knowing your biological age may provide an incentive to lead a healthier lifestyle.

Different Measurements

Your chronological age is a measurement of how many days you've been alive. Your biological age is a measurement of how much life you likely have left, based on your physiology at any given time.

How Biological Age Is Determined

Changes in your genetic material are key to determining your biological age. Researchers look at two things:

  • Telomeres (part of chromosomes)
  • DNA methylation (how your DNA is aging)


Each strand of DNA is made up of chromosomes, which carry your genetic information. They look like X's (except for the one that determines male sex characteristics, which looks like a Y).

At the tip of each point of the X (or Y) is a small structure called a telomere. Scientists have discovered that telomeres get shorter with chronological age.

Research on Telomeres and Biological Age

One study found that people with shorter telomeres were more likely to have:

  • Chronic illness
  • A neurodegenerative disorder
  • An early death

In other words, if you have shorter telomeres than someone born the same time as you, you're biologically older than them.

Another study suggests that maintaining (or adopting) a healthy lifestyle can actually reverse the aging process by lengthening telomeres.

DNA Methylation

It's common to think of DNA as something that's fixed and unchanging, but that's not accurate. You actually have many more genes than show up at any given time. Some are turned "on," others are turned "off."

When a gene is on, it's being "expressed." For example, say you have a gene that influences your immune system that's been expressed since you were born. At some point in your life, you may be exposed to environmental pollution or an illness that switches that gene off.

After that, you may get sick a lot more often or be predisposed to certain chronic illnesses. Your immune system has changed at the genetic level.

The process that turns genes on or off is called methylation.

Research on Methylation and Biological Age

One study sought to discover whether DNA methylation is an accurate way of predicting age. Researchers gathered 8,000 samples of 51 different tissues and cells.

Looking at methylation rates, most of the tissue and cell samples studied had the same chronological and biological ages. But some didn't.

Researchers concluded that certain parts of the body age faster than others. For example, healthy breast tissue can be as much as three years older than the rest of your body. If it's next to cancerous tissue, it's an average of 12 years older.

Using the methylation-based method of determining biological age, researchers can determine the risk of breast cancer. If you have female breast tissue, every five years older you are biologically than chronologically, your breast cancer risk is 15% higher.

Sex exists on a continuum. This article uses binary sex designations to accurately reflect the classification of study participants, which are generally limited to male and/or female.

Factors That Determine Biological Age

If you want to lower your biological age, you have multiple options. And they're generally the same options you've heard about for being healthy in general.


A 2018 study on nutrition and biological age suggests that eating a high-nutrient diet can lower your biological age.

Researchers looked at how much nutrition data people considered when deciding what foods to buy. The more attention paid, the lower the biological age. The difference was more significant in people who:

  • Have chronic disease
  • Have a family history of chronic disease
  • Have obesity
  • Are older
  • Have a lower education level

They also found a sex-based difference when it came to choosing foods: just under 13% of males thought about nutrition data at the grocery store, compared to 27.5% of females.

Other studies on diet and biological age suggest the ideal diet is:

  • Low in calories
  • Plant-based
  • High in fish
  • A Mediterranean diet

You should always talk to your healthcare provider before making significant changes in your diet or activity level. They can help you determine what's healthiest for you based on your complete medical history, diagnoses, and medications.


Research into biological aging has revealed a connection between higher activity levels and lower biological age.

Not all studies agree that increased exercise has an impact on biological age. However, a growing body of research supports the idea that it does.

  • A 2021 study on post-menopausal women showed a slowdown in some biomarkers of age and disease, including cancer.
  • A 2022 study showed that changing the diet and adding more exercise lowers your biological age more than either dietary changes or increased exercise alone.
  • A 2020 study found that people trained with aerobic exercise were almost 5.5 years younger than people who were sedentary.

If you've been sedentary and want to increase your activity level, check with your healthcare provider and start slowly.


Physical and psychological stress both increase the biological age, but in a way that appears to be reversible.

A 2022 study monitored the effects of stressors such as:

  • Pregnancy
  • COVID-19 infection
  • Trauma
  • Surgery

They found a rapid increase in biological age (measured by DNA methylation) during the stressful time. However, it went back to baseline within a few days of the stressor being removed.

In a 2021 study on psychological stress and biological aging, researchers found that people who are emotionally resilient and able to regulate their emotions were able to avoid the aging effects of stress.

If you have significant physical or psychological stressors in your life, talk to your healthcare provider about ways to reduce or eliminate that stress. You may benefit from seeing a mental health therapist.


Smoking has long been known to cause serious health problems and shorten your lifespan. Studies show that smoking increases your biological age.

As with stress, though, smoking-related age advancement appears to be reversible. When researchers compared current smokers, former smokers, and people who've never smoked, they found that the biological age of former smokers was the same as that of non-smokers.

If you need help giving up smoking, talk to your healthcare provider about options such as medications or emotional support.

Sleeping Habits

Poor sleep quality has a negative impact on your health and longevity, and it's also been found to increase your biological age.

Adults should get at least seven hours of sleep every night. However, many people don't. This may be due to lifestyle factors or sleep disorders. Sleep quality is also important when it comes to your health.

If you're able to get more and/or better sleep, you can reverse the biological aging it caused, according to researchers.

You may be able to improve your sleep duration or quality by making simple changes, such as going to bed earlier, turning off screens half an hour before bed, or reducing distractions in the bedroom.

If you're unable to get better sleep on your own, talk to your healthcare provider about it. You may have a sleep disorder that needs to be diagnosed and treated.

Physical Environments

Your physical environment includes where you live, work, and spend significant amounts of time. Your environment determines the amount of air pollution and other contaminants or hazardous materials you're exposed to.

Those toxins can speed up your biological aging. You may be able to take steps to avoid or reduce some of your exposure. Research suggests this could help reverse the effects.

However, it may be difficult to cut out some of these hazards. Fortunately, research shows that other healthy changes, such as more or better sleep, can reverse the aging caused by pollution.

If you're exposed to hazardous materials at work, make sure you and your employer are following all safety procedures.

Calculating Your Biological Age

There's no simple way for you to calculate your biological age. It takes medical tests and a healthcare provider to accurately determine it. So, to learn your true biological age, ask your healthcare provider about it.

Some websites claim to have biological age calculators, and they may take into account some of the factors that influence your biological age. However, without access to your test results, they're not scientifically valid.

At least one commercial test is available that claims to determine your biological age. The website currently lists the price as $499 and says it uses a saliva sample that you collect yourself. It's not clear whether this test has been scientifically validated.

Some websites, including Ageless Rx and Longevity Advantage, offer calculators where you can enter the results of a blood test to get your biological age. You may be able to use recent routine test results for this. However, these calculators may not be valid and results may not be accurate.

Your best bet is to go through your healthcare provider, who can then interpret the results for you and help you come up with ways to improve your biological age and overall health.


Your chronological age is a measurement of how long you've lived. Your biological age is a prediction of how long you have left and how likely you are to become chronically ill.

Determining your biological age requires medical tests for telomere length and biomarkers of DNA methylation, which is the process by which DNA is changed throughout your lifetime.

Unlike chronological age, your biological age can be changed. Things like diet, exercise, stress levels, sleep quality, and smoking can affect your biological age, and changing your habits can make a big difference.

Commercial tests and online calculators claiming to measure biological age may not be valid. To determine your biological age, ask your healthcare provider for the tests.

19 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Poganik JR, Zhang B, Gaht GS, Kerepesi C, Yim SH, et al. Biological age is increased by stress and restored upon recovery. bioRxiv. doi:10.1101/2022.05.04.490686

  2. Anitha A, Thanseem I, Vasu MM, Viswambharan V, Poovathinal SA. Telomeres in neurological disorders. Adv Clin Chem. 2019;90:81-132. doi:10.1016/bs.acc.2019.01.003

  3. Arsenis NC, You T, Ogawa EF, Tinsley GM, Zuo L. Physical activity and telomere length: Impact of aging and potential mechanisms of action. Oncotarget. 2017;8(27):45008-45019. doi:10.18632/oncotarget.16726

  4. Horvath S. DNA methylation age of human tissues and cell types. Genome Biol. 2013;14(10):R115. doi:10.1186/gb-2013-14-10-r115

  5. Kresovich JK, Xu Z, O'Brien KM, Weinberg CR, Sandler DP, Taylor JA. Methylation-based biological age and breast cancer riskJ Natl Cancer Inst. 2019;111(10):1051-1058. doi:10.1093/jnci/djz020

  6. Han KT, Kim DW, Kim SJ, Kim SJ. Biological age is associated with the active use of nutrition dataInt J Environ Res Public Health. 2018;15(11):2431. Published 2018 Nov 1. doi:10.3390/ijerph15112431

  7. Johnson AA, English BW, Shokhirev MN, Sinclair DA, Cuellar TL. Human age reversal: Fact or fiction?Aging Cell. 2022;21(8):e13664. doi:10.1111/acel.13664

  8. Esposito S, Gialluisi A, Costanzo S, et al. Mediterranean diet and other dietary patterns in association with biological aging in the Moli-sani Study cohortClin Nutr. 2022;41(5):1025-1033. doi:10.1016/j.clnu.2022.02.023

  9. Ashiqur Rahman S, Giacobbi P, Pyles L, Mullett C, Doretto G, Adjeroh DA. Deep learning for biological age estimationBrief Bioinform. 2021;22(2):1767-1781. doi:10.1093/bib/bbaa021

  10. Sillanpää E, Ollikainen M, Kaprio J, et al. Leisure-time physical activity and DNA methylation age-a twin studyClin Epigenetics. 2019;11(1):12. Published 2019 Jan 19. doi:10.1186/s13148-019-0613-5

  11. Fiorito G, Caini S, Palli D, et al. DNA methylation-based biomarkers of aging were slowed down in a two-year diet and physical activity intervention trial: the DAMA studyAging Cell. 2021;20(10):e13439. doi:10.1111/acel.13439

  12. Ho E, Qualls C, Villareal DT. Effect of diet, exercise, or both on biological age and healthy aging in older adults with obesity: Secondary analysis of a randomized controlled trialJ Nutr Health Aging. 2022;26(6):552-557. doi:10.1007/s12603-022-1812-x

  13. Lehallier B, Shokhirev MN, Wyss-Coray T, Johnson AA. Data mining of human plasma proteins generates a multitude of highly predictive aging clocks that reflect different aspects of agingAging Cell. 2020;19(11):e13256. doi:10.1111/acel.13256

  14. Harvanek ZM, Fogelman N, Xu K, Sinha R. Psychological and biological resilience modulates the effects of stress on epigenetic agingTransl Psychiatry. 2021;11(1):601. Published 2021 Nov 27. doi:10.1038/s41398-021-01735-7

  15. Centers for Disease Control and Prevention. Tobacco-related mortality.

  16. Pyrkov TV, Getmantsev E, Zhurov B, et al. Quantitative characterization of biological age and frailty based on locomotor activity recordsAging (Albany NY). 2018;10(10):2973-2990. doi:10.18632/aging.101603

  17. Gao X, Huang N, Guo X, Huang T. Role of sleep quality in the acceleration of biological aging and its potential for preventive interaction on air pollution insults: Findings from the UK Biobank cohortAging Cell. 2022;21(5):e13610. doi:10.1111/acel.13610

  18. Centers for Disease Control and Prevention. How much sleep do I need?

  19. American Academy of Sleep Medicine: Sleep Education. Healthy sleep habits.

Additional Reading

By Sharon Basaraba
Sharon Basaraba is an award-winning reporter and senior scientific communications advisor for Alberta Health Services in Alberta, Canada.