Chronological Vs. Biological Aging: What To Know

Aging refers to the process of becoming older. When discussing age, people typically use their chronological age, which is how many years have passed since their birth.

However, people of the same chronological age may have a different biological age. This describes the age of their cells, which is modifiable and may account for why some people appear younger and healthier compared to others of the same chronological age.

Chronological age is the most common way that people measure age. It simply refers to the time that has elapsed since birth and is typically the age that people identify with.

Although this is the most common way of determining age, it only measures the passage of time and may not accurately reflect the aging process. This is because chronological aging is linear, meaning it increases sequentially and a person cannot accelerate or delay chronological aging.

Also known as physiological or functional age, biological aging refers to the age of cells and relates to a decline in their function. It aims to provide a more accurate measure of age and could be a better predictor of health.

While chronological age is linear, many genetic and environmental exposures can influence biological aging. The pace of biological aging can be faster or slower than chronological aging. This can result in a difference between ages, which health experts may describe as an age gap.

This age gap can help explain the considerable variation in the health and appearance of individuals that are the same chronological age. For example, lifestyle choices such as smoking can accelerate a person’s biological age, while regular exercise may help to slow the biological aging process.

By using biomarkers, which refer to molecules that are signs of normal or abnormal processes, scientists may be able to establish a person’s biological age.

The main difference between chronological and biological aging is that chronological age occurs on a fixed path, while biological age varies between individuals of the same chronological age. Genetic and environmental exposures influence biological aging, meaning it may be possible to modify biological age.

As biological age may be a better predictor of morbidity and mortality than chronological age, it may serve as a better indicator for providing optimal healthcare.

Senescence is a term that describes the process of growing old. Biologically, it refers to the process where cells age and lose the ability to divide but do not die. Instead of being removed, these cells remain in the body and release chemicals that can damage neighboring cells.

In some cases, cell senescence can be beneficial, such as with wound healing. However, it can also negatively affect health. As a person ages, the amount of senescent cells in their body increases. As they accumulate, this can affect a person’s ability to withstand stress or illness, recover from injuries, or learn new things.

As such, cell senescence relates to a variety of age-related conditions, as well as declines in eyesight, mobility, and thinking ability.

Different factors that contribute to cellular aging include:

• Oxidative stress: This refers to an imbalance between free radicals and antioxidants in the body. When there are too many free radicals and not enough antioxidants, the free radicals can damage cells and play a role in aging.
• Genomic instability: This is a hallmark of aging and refers to a higher frequency of DNA alterations that occur during cell division.
• Mitochondrial genome damage: Mitochondria play a key role in generating energy for cells to function. Growing evidence suggests that mitochondrial dysfunction is another hallmark of aging.
• Telomere shortening: A telomere is a region of DNA at the end of a chromosome, which protects it from damage. However, a telomere shortens with age. Eventually, a telomere becomes so short that a cell is no longer able to divide successfully, and the cell dies.
• Certain genes: Some genes play a larger role in the aging process than others. For example, variations in certain genes significantly impact lifespan and can manifest as premature aging.

Chronological age is a person’s age in years since their birth, while biological age refers to the age of a person’s cells. Chronological age occurs on a linear path, while biological age is modifiable. As such, these ages can differ, and a person may be able to lower their biological age.

Biological aging may represent the aging process more accurately than chronological age. Improvements in estimating a person’s biological age may help to improve guidelines for healthcare.