What is the difference between chronological age and biological age?

Chronological age advances uniformly for everyone, while biological age reflects the actual condition of the body. The two do not necessarily match, even in the same person.

We each have "two ages." One is chronological age, which advances uniformly for everyone with each birthday. The pace at which the calendar moves forward is the same for everyone.

Some people at 40 by the calendar have bodies closer to their sixties, while others retain the vigor of someone in their twenties. It is the "speed of aging" that creates this difference.

Why do individual differences in aging speed occur?

Large-scale studies show significant differences in biological age even among people of the same chronological age, and that the speed of aging also differs by organ.

The Dunedin Study: At the Same Age of 38, Biological Age Ranged from 28 to 61

In conclusion, individual differences in aging speed already exist from one's twenties. Dr. Moffitt's research team followed 954 young people at three time points — ages 26, 32, and 38 — measuring 18 items including blood, heart, lungs, kidneys, and liver (1).

There were also differences in the pace of aging. Some people aged the equivalent of 1 year per year, while others aged the equivalent of 3 years per year (1). Aging was already progressing from one's twenties, not just in old age.

Stanford Study: Aging Speed Differs by Organ

In 2023, the Wyss-Coray lab at Stanford University analyzed blood from 5,676 people and used machine learning to estimate the "age" of each of 11 organs (2).

What became clear is that even within a single person's body, the speed of aging differs by organ (2). The whole body does not age uniformly.

This unevenness can also be a warning sign of risk. It was reported that people with accelerated heart aging had about a 2.5-fold increase in heart failure risk, and that accelerated aging of the brain and blood vessels could predict the progression of Alzheimer's disease (2).

What are the two factors that determine aging speed?

The speed of aging is determined by two factors: lifestyle habits and genetics (DNA). Twin studies show that 20–30% of lifespan is explained by genetics.

Factor 1: Lifestyle Habits

The first factor is lifestyle. Diet, exercise, sleep, and stress directly affect the body's aging speed. These are elements you can improve yourself.

Factor 2: Genetics (DNA)

Individuality in "how one faces aging" — such as resistance to oxidative stress, cellular repair capacity, and susceptibility to inflammation — is encoded in DNA (3). The difference between "someone who stays healthy despite an unhealthy lifestyle" and "someone who tires easily" is also explained by a combination of genetic predisposition and environment.

However, genes are not destiny. By knowing your predispositions and choosing your lifestyle accordingly, you can change your future rate of aging.

What are the benefits of knowing your own aging tendencies?

Knowing your genetic tendencies lets you choose the countermeasures you actually need. The benefit is avoiding anti-aging approaches based on passing trends.

In conclusion, the first thing to do is find out "where you are most prone to aging." The reason is that the priority of countermeasures differs from person to person.

For example, someone whose blood vessels age quickly and someone whose brain ages quickly need to focus on different lifestyle habits. By understanding your own weak points, you can concentrate your limited time and energy on the countermeasures you truly need.

One way to do this is through genetic testing. seeDNA's "DNA Score" analyzes numerous DNA regions related to disease risk and constitution, expressing your genetic tendencies as numerical values (4). A future of health and vitality begins with today's choices.