Chronological age vs biological age: what's the difference?
Chronological age, also called calendar age, is how long you have been alive.
Biological age estimates how your body compares at that age.
Chronological age counts the years since your date of birth. Biological age estimates how your body compares with what is typically expected at that age.
Two people can share a chronological age and still age very differently.
What is chronological age?
Chronological age, also called calendar age, is the number of years since your date of birth.
If you were born 40 years ago, your chronological age is 40.
It moves forward at the same speed for everyone. It does not account for sleep, fitness, stress, recovery, activity, or other factors that may affect how you feel and function.
Your birthday measures time. It does not measure how you are ageing.
What is biological age?
Biological age is an estimate of how your body compares with what is typically expected at your chronological age.
Researchers can estimate biological age using different signals, including physical function, physiological measurements, biomarkers and, in some methods, molecular or epigenetic data.
This means two people who are both 45 may have very different biological-age estimates.
There is no single universally accepted biological-age test, and different methods can produce different results.
Biological age vs pace of ageing
Biological age and pace of ageing are related, but they are not identical.
Biological age estimates where your body appears to be on an ageing trajectory.
Pace of ageing describes how quickly age-related changes are happening over time.
One is closer to position. The other is speed.
What affects biological ageing?
Research on biological ageing looks at many influences. Dayline does not measure all of them. They include:
- sleep
- physical activity
- fitness
- stress
- nutrition
- smoking
- alcohol
- environment
- genetics
- overall health
One bad night of sleep does not suddenly make you biologically older. The more useful signal is the pattern over time.
Biological age and healthspan
Healthspan is the part of your life spent in good health.
It is different from lifespan, which is simply how long you live.
Biological-age research is useful because it helps explore why some people stay healthier and function better for longer than others of the same chronological age.
A younger biological-age estimate does not guarantee a longer life.
How Dayline shows Bio Age
Dayline Bio Age takes a lifestyle-based approach.
It looks at patterns in the life data you choose to connect, such as health, calendar, email, and weather. It does not use lab biomarkers, genetics, or epigenetic data.
Dayline then combines Bio Age with your daily Battery and one clear action for what to do next.
Your days shape your years.
Instead of showing another isolated score, Dayline helps you understand the pattern behind your data and whether your lifestyle is moving in a better or worse direction over time.
Dayline Bio Age is not a blood test, epigenetic clock, or medical measurement.