Chapter 2

What is Biological Age Exactly?

People age at different rates. Some faster, some slower. 

Yet society uses an age measure that fails to capture this fact. That age measure is chronological age, a simple addition of all the Earth years that have passed since you were born. A birthday is a celebration of this milestone—the milestone of having been alive another Earth year. Chronological age is the sum of all your birthdays.

Public institutions use this form of age calculation to determine when an individual can legally work, drink alcohol, engage in sexual intercourse, vote, or enter into a contract. It’s the age printed on state-issued documents such as your driver’s license.

However, it does not account for the varying ageing rates between people. Someone 50 years old, maybe 40 years old biologically. Similarly, someone else may be 50 also but maybe 55 years old biologically—a 15-year difference between the two people of the “same age.”

This disparity is rapidly becoming a societal issue because:

  1. Ageing therapies, drugs, and supplements that slow or reverse ageing are emerging as a scientifically validated market category.
  2. During the last decade, science has made significant progress in measuring an individual’s actual age and rate of ageing.

This “actual” age is termed biological age. Different from chronological age, there’s no single method to calculate it and none as simple as counting the number of rotations around the Sun since birth.

Instead, science’s frontiers are being pushed forward by an expanding variety of methods ranging from the complex to the highly complex.

Complicating matters further – various organs and systems within the body age at different rates. For example, an individual’s immune system may age more quickly than their cardiovascular system, their liver may age faster than the heart, and their kidneys may age more rapidly than the skin.

Numerous scientific methods now capture actual age more accurately than chronological age, account for individual differences in ageing, and quantify an individual’s rate of ageing.

Next Chapter
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