Biological Age
An estimate of how old the body is functionally, based on objective biological measurements, as opposed to chronological age, which simply counts years since birth.
Biological age is a measure of the body's functional state relative to the population average at a given age. It is derived from objective biological measurements including DNA methylation patterns (epigenetic clocks), blood biomarker panels, physiological performance tests, and telomere length.
A person with a biological age lower than their chronological age has aging biomarkers resembling those of younger individuals. A person with a biological age higher than their chronological age shows markers consistent with accelerated aging relative to peers.
Biological age is not a single number from a single test. It is an estimate, and different measurement systems produce different estimates based on what they measure. The most validated methods currently are epigenetic clocks, particularly GrimAge and DunedinPACE, which use DNA methylation patterns to estimate aging pace and predict healthspan decline.
A 55-year-old who has trained consistently, slept well, managed metabolic health, and avoided smoking might have an epigenetic age of 48, suggesting their cellular aging is running roughly 7 years behind their chronological age. A sedentary 55-year-old with poor metabolic health might test at a biological age of 63.