What is biological aging and how do we measure it?

Terri Petkau, PhD

Longevity Scientist, Connect Health

 Aging involves the gradual deterioration of the physiological functions that are necessary for survival over time. A person’s chronological age is well-defined and easy to measure; it is the number of years that have passed since the day you were born. ‘Biological age’ refers to the speed at which your cells, tissues, and organs are aging, which can differ from chronological age.  Some individuals seem to age slower than their chronological age would predict, while others may age faster; this reflects differences in biological aging.

Many physiological markers change quite predictably with age, including DNA methylation, telomere length, and a variety of other blood-based biomarkers. Over the past decade, biological age ‘clocks’ based on all of these markers have been developed, each with its own strengths and limitations. The ability to use biological aging clocks to reliably measure how fast an individual is aging is an invaluable tool for longevity medicine, as it provides us with a metric to evaluate how well lifestyle and other interventions are working. However, the evidence that is available to date suggests that biological age clocks are not yet ready to be used independently as a clinical decision-making tool. We still don’t have enough data from clinical studies to understand how these clocks relate to other established measures of physiological function nor whether or not they accurately predict health status in the absence of other clinical data.

A recent paper¹ from Dr. Andrea Maier’s research group at the National University of Singapore evaluated a variety of DNA methylation clocks in a cohort of ‘the oldest old’ for their association with standard clinical measures of physical function and physical performance. The study tested multiple clocks on a cohort of community-dwelling adults living in Singapore. After collecting data from 433 individuals and analyzing it for associations, the study concluded that the GrimAge2 clock² correlated most closely with the established measures of physical function and physical performance. The authors correctly emphasized that this is still a study of association and that causality – the idea that what the GrimAge2 clock (or any other aging clock) is measuring is causally related to changes in physical function, remains to be determined. Both longitudinal and interventional studies are needed to improve our understanding in this area.

At Connect Health, we strongly support the concept of biological aging, i.e., that your cells, tissues, and organs may age faster or slower than is predicted by chronological age. Targeting the process of biological aging is, in essence, the goal of longevity medicine. Connect Health is committed to supporting the scientific field of aging biology and clinical research in healthy longevity. We use biological aging clocks in combination with the deep data sets that we collect on all of our clients in an effort to understand how such clocks might best be applied in clinical medicine. Our hope is that, with a combined effort, we can grow the body of evidence that describes how biological aging clocks are and are not useful in the clinical practice of longevity medicine.

1          Tay, J. et al. J Gerontol A Biol Sci Med Sci (2025). PMID: 39869450

2          Lu, A. T. et al. Aging (Albany NY) 14, 9484-9549 (2022). PMID: 36516495