Chronological age and biological age could differ. Biological age is the age of one's cells and tissues as established by physiological data, whereas chronological age is the length of one's existence. If a person is very healthy and physically fit for their age, their biological age may be different from their chronological age. But, if a person is inactive, has a chronic illness, or is physically unfit, their biological age may be higher. The beginning of disease and mortality are predicted by biological age more precisely than by chronological age, according to studies.

Chronological vs. biological age

Chronological age cannot be changed. After being born on a specified day, one has lived on the planet for a predetermined length of time. No matter how much some individuals would want to, they can't alter that. Nonetheless, one has undoubtedly seen a few people whose chronological age astonished them since they seemed to be significantly older or younger than they actually were. Their biological age might not exactly match their chronological age. Aging is mostly determined by genetics, which is outside of a person's control. Yet, evidence suggests that aging may be influenced by environmental factors such as diet, exercise, stress, smoking, sleep habits, and the physical environment.

Biological age, also known as physiological age, is influenced by all of these variables and more. According to experts, all of those events can be seen in the state of your DNA (genetic material). Since biological age can assist in predicting issues like diabetes, dementia, and when one will die, it's feasible that in the future it will surpass chronological age as the most important element in predicting one's health. Additionally, one will probably be able to influence biological aging and even become "younger" by adopting healthy lifestyle choices. Knowing one's biological age may inspire one to lead a healthier lifestyle.

Biological age determination: telomeres

Each DNA strand is assembled into chromosomes, which hold a person's genetic material. They look like Xs (except for the one that determines male sex characteristics, which looks like a Y). A little component at the tip of each X (or Y) point is called a telomere. Age-related telomere length decline has been discovered by researchers.

One study found an increased risk of developing chronic diseases, neurological problems, and early death among people with shorter telomeres. In other words, if someone has shorter telomeres than someone who was born at the same time, that person is physiologically older. A different study found that maintaining a healthy lifestyle and lengthening telomeres can significantly decrease the aging process.

DNA methylation

Contrary to popular belief, DNA is not something that is static and unchanging. One has a lot more genes than are active at any given time. Some genes are "on," while others are "off." A gene is "expressed" when it is "on." Consider a person who possesses an immune system-influencing gene that has been expressed since birth. They could come into contact with environmental toxins or contract a disease at some time in their lives, turning that gene off. After then, a person may become ill much more frequently or be more susceptible to developing certain chronic illnesses. Genetic changes have been made to the immune system. Methylation is the mechanism that controls whether or not genes are active.

Factors determining biological age: diet

A high-nutrient diet may help one's biological age, according to a 2018 study on nutrition and biological age. Researchers examined how much people thought about nutrition information when choosing which foods to buy. The biological age decreases as more attention is given to it. Those with chronic diseases, those with a family history of chronic diseases, obesity, older age, and lower levels of education showed a greater disparity. When it comes to selecting goods, they also discovered a sex-based difference of slightly under 13% of men and 27.5% of women in the grocery store gave nutrition information some thought. The Mediterranean diet, which is low in calories, plant-based, and heavy in fish, is suggested by other studies on diet and biological age.

Exercise

Research on biological aging shows that higher levels of activity are linked to younger biological ages. Studies don't always support the idea that more exercise has an impact on biological age. But, a growing body of studies is leaning that way. Research on post-menopausal women in 2021 found that several age- and disease-related indicators, including cancer, were slowing down. According to a study from 2022, modifying your diet and upping your activity level has a greater impact on reducing your biological age than just doing either of those things alone. A 2020 study found that people who exercised aerobically were more than 5.5 years younger than people who were inactive.

Stress

The biological age is increased by both physical and psychological stress, but in a way that might be reversible. The consequences of stressors such as pregnancy, COVID-19 infection, trauma, and surgery were studied in 2022. They discovered that throughout the stressful period, biological age (as determined by DNA methylation), increased quickly. Yet, after the stressor was eliminated, it returned to baseline in a short while. Researchers concluded in a 2021 study on the relationship between psychological stress and biological aging that persons who have emotional resilience and emotional control are able to prevent the biological impacts of stress.

Smoking

Smoking has long been recognized to limit lifespan and result in major health issues. According to studies, smoking accelerates biological aging. But smoking-related aging seems to be reversible, just like stress. Researchers observed that the biological ages of former smokers were the same as those of non-smokers when they compared those of present smokers, former smokers, and non-smokers.

Sleeping habits

Inadequate sleep has been demonstrated to accelerate biological aging and has a detrimental effect on health and longevity. People should sleep for a minimum of seven hours each night. Many individuals don't, though. Sleep issues or lifestyle factors may be to blame for this. When it comes to health, sleep quality is also crucial. According to studies, one can stop the biological aging it causes if they are able to get more and/or better sleep. By making small adjustments, such as getting to bed earlier, shutting off devices an hour before bed, or decreasing distractions in the bedroom, one may be able to increase the quantity or quality of their sleep.

Physical environment

The physical environment of an individual is made up of the locations where they reside, go to work, and spend a lot of time. The degree to which one is exposed to air pollution, other poisons, and hazardous substances depends on the surroundings. These poisons are capable of accelerating biological aging. One could make an attempt to avoid or reduce part of this exposure. Research indicates that this could help reverse the consequences. It might be difficult to eliminate some of these dangers, though. However, research suggests that altering other healthy behaviors, such as sleeping more or better, can prevent the impacts of pollution-induced aging.

Conclusion

A person's chronological age is a measure of their life span. The biological age is a predictor of how long someone has to live and the likelihood that they may develop a chronic illness. Medical tests for telomere length and biomarkers of DNA methylation—the process by which DNA is altered over the course of a lifetime—is necessary to establish biological age. Contrary to chronological age, biological age is modifiable. Biological aging can be influenced by factors like nutrition, exercise, stress levels, sleep quality, and smoking, and modifying behaviors can have a significant impact.

(Co-written with Evan Sabih)

Notes

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.
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.
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.
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.
Kresovich JK, Xu Z, O'Brien KM, Weinberg CR, Sandler DP, Taylor JA. Methylation-based biological age and breast cancer risk. J Natl Cancer Inst. 2019;111(10):1051-1058. doi:10.1093/jnci/djz020.
Han KT, Kim DW, Kim SJ, Kim SJ. Biological age is associated with the active use of nutrition data. Int J Environ Res Public Health. 2018;15(11):2431. Published 2018 Nov 1. doi:10.3390/ijerph15112431.
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.
Esposito S, Gialluisi A, Costanzo S, et al. Mediterranean diet and other dietary patterns in association with biological aging in the Moli-sani Study cohort. Clin Nutr. 2022;41(5):1025-1033. doi:10.1016/j.clnu.2022.02.023.
Ashiqur Rahman S, Giacobbi P, Pyles L, Mullett C, Doretto G, Adjeroh DA. Deep learning for biological age estimation. Brief Bioinform. 2021;22(2):1767-1781. doi:10.1093/bib/bbaa021.
Sillanpää E, Ollikainen M, Kaprio J, et al. Leisure-time physical activity and DNA methylation age-a twin study. Clin Epigenetics. 2019;11(1):12. Published 2019 Jan 19. doi:10.1186/s13148-019-0613-5.