Biological Variability
Definition
Biological variability is the natural variation seen within and between living systems, including differences between individuals, tissues, cells, time points, and repeated measurements. In ageing research, it helps explain why people of the same chronological age can differ substantially in biological age, disease risk, resilience, and biomarker values. [1] [2]
Why It Matters in Ageing Research
Biological variability matters because ageing is heterogeneous. Some variation reflects meaningful biology, such as genetic background, environment, disease history, tissue state, or immune function, while some reflects measurement noise or short-term fluctuation. Distinguishing these sources of variation is important when interpreting biomarkers, cohort studies, intervention effects, and claims about biological age. [2] [3]
Common Confusion
- Biological variability is not the same as measurement error, although both can affect study results.
- Variation between people does not automatically mean a biomarker is unreliable; it may reflect real biological differences.
- A single biomarker value may not represent a stable long-term state if the marker changes with time, illness, sampling conditions, or laboratory methods.
Related Reading
References
- Fraser, C. G. (2001). Biological variation: From principles to practice. AACC Press. https://www.aacc.org/science-and-research/scientific-shorts/2018/biological-variation
- Ferrucci, L., Levine, M. E., Kuo, P. L., & Simonsick, E. M. (2018). Time and the metrics of aging. Circulation Research. https://pmc.ncbi.nlm.nih.gov/articles/PMC6380373/
- Cohen, A. A., Kennedy, B. K., Anglas, U., et al. (2020). Lack of consensus on an aging biology paradigm? A global survey reveals an agreement to disagree, and the need for an interdisciplinary framework. Mechanisms of Ageing and Development. https://pmc.ncbi.nlm.nih.gov/articles/PMC7564088/
This glossary entry is provided for educational purposes only and does not constitute medical advice.