The Utility of Biological Age Tests

Interest in biological age testing is growing quickly, but experts caution that the science is still evolving. In a February 2026 editorial, The Lancet examined the rise of commercial “biological age” tests and questioned how useful they are in clinical care today.

Unlike chronological age, which simply counts the years since birth, biological age aims to estimate how well a person’s body is functioning. The idea is that two people who are, for example, both 50 years old on paper may have bodies aging at different speeds depending on genetics, lifestyle, stress, and environment. Biological age tests seek to measure this difference.

Many popular tests estimate what is known as “epigenetic age.” These tests measure patterns of DNA methylation, a natural chemical tagging process that helps turn genes on or off. Over time, methylation patterns shift in predictable ways. Scientists use algorithmic models to compare a person’s methylation profile to large datasets and estimate whether their body appears biologically older or younger than expected.

However, most of these clocks are built on statistical associations. They detect patterns that correlate with aging, but they do not always prove that methylation changes directly cause disease or organ decline. The editorial team points to a 2025 study in eBioMedicine, which attempted to move beyond simple correlation by combining long-term population data with genetic analyses. In the study, researchers identified specific methylation sites linked to colorectal cancer risk, suggesting that accelerated biological aging may increase vulnerability to certain diseases earlier in life. While promising, this research does not yet establish clear cause-and-effect pathways.

There are also practical limitations. Most epigenetic clocks rely on blood or saliva samples, which may not reflect aging processes in other organs and tissues. Different tests often produce different results because they are trained on different populations and use different algorithms, so that there is a high variability in results depending on which company's test kit is employed. No single model has yet emerged as clearly superior. Biological aging patterns can also vary by sex, lifestyle, environment, and disease stage, and these differences are not always consistently accounted for.

Some studies suggest that heart-healthy behaviors, such as exercise and good diet, are associated with slower biological aging. A few clinical trials have even begun using epigenetic clocks as outcome measures. Still, experts note that we do not yet know whether these tools can reliably track meaningful changes over time.

Biological age testing holds immense potential for improving disease prevention and understanding how aging relates to chronic disease. But before these tests can become routine clinical tools, The Lancet's leadership says key scientific and methodological gaps remain to be addressed. For now, the numbers these tests generate should be interpreted with caution rather than treated as definitive measures of how fast someone is truly aging.