Biological Age Tests Show Promise for Disease Prevention, But Experts Urge Caution on Consumer Interpretation
Key Insights
Scientists broadly agree that biological age is a valid concept distinct from chronological age, measurable through various molecular clocks that track processes like DNA methylation and chronic inflammation.
Epidemiological studies show that accelerated biological aging, as measured by clocks such as GrimAge and iAge, can predict higher risks of cognitive decline (search), heart disease (search), and frailty (search).
Experts warn that consumer-available tests capture only individual facets of aging and are open to misinterpretation, with single age estimates providing limited clinical value without functional health metrics.
In recent years, the concept of biological age—a measure of cellular and organ health distinct from chronological age—has moved from research laboratories into public consciousness, fueled by celebrity endorsements and a growing commercial testing market. Yet while scientists working in the aging field broadly agree that the underlying notion is valid, they caution that the information offered by biological aging clocks is open to misinterpretation and that the commercial landscape has been muddied by unvalidated products.
"Biological age is real," says David Furman, a professor at the Buck Institute for Research on Aging. "There's a difference between your chronological age and your biology, that's for sure, and we can measure it by various means."
The Science Behind Aging Clocks
Biological aging clocks—the term given to the suite of tests that attempt to measure biological aging using blood or saliva—have demonstrated meaningful predictive power in epidemiological research. Faster aging according to GrimAge, a commonly used aging clock that measures DNA methylation in the blood, appears to predict individuals at a higher risk of cognitive decline (search). Research has also suggested that iAge, a clock which tracks chronic inflammation, can predict greater vulnerability to heart disease (search) and frailty (search).
Because of this, Andrea Maier, professor of medicine and functional aging at the National University of Singapore, suggests that these tests could be used as early "alarm systems" to flag people who might benefit from therapeutic or lifestyle interventions. "Because you know that they're at higher risk, you can then actively intervene," Maier says.
A newer method, devised by Vadim Gladyshev from Harvard Medical School and colleagues, is based on patterns of gene activity collected from more than 4,000 people, as well as data from mice, rats, and macaques. The researchers believe this method is more sensitive than its predecessors and could shorten the otherwise lengthy clinical trials needed to determine if anti-aging treatments work. For now, this test remains for research purposes only.
The Limits of Consumer Testing
Despite the scientific promise, experts emphasize that the tests available to consumers capture only individual facets of aging. Bradley Elliott, a researcher at the University of Westminster and trustee for the British Society for Research on Ageing, explains that tests such as GlycanAge measure biomarkers reflecting immune function, while microbiome clocks estimate the aging of the gut. But aging is a progressive process governed not merely by lifestyle but by innate genetic programming.
"Aging is something that happens to all of us," Elliott says. "Even if we optimize everything, it's [only] the rate of change which is modifiable."
Maier cautions that a single age estimate from one clock is not especially informative. Instead, results from multiple clocks combined with functional health metrics such as VO2max, a measure of respiratory health, will provide a more accurate overview. "We need to look at different organs," says Furman. "One overall age number doesn't help, you need to know more granular details. For example, if the heart is plus five [years] it's suffering. If you have minus three [years] for the kidneys, that's protecting you."
Consumers also need to understand that biological age estimates can vary over the course of the day, meaning that repeat testing should occur at the same time. Estimates can also fluctuate in response to physical activity. One 2025 study using DNA methylation clocks to assess professional German soccer players discovered that tests taken immediately after a match showed them appearing biologically much younger, but measurements returned to normal a few hours later.
Psychological Risks and the Need for Standards
When people discover they appear to be biologically older, the results can fuel significant health anxiety. "I've had patients who absolutely had a psychological crisis," says Maier. "They think it's a death sentence if a clock shows that they're 10 years older."
The commercial landscape has further complicated matters, with a proliferation of companies launching algorithms that purport to estimate biological age using selfies or surveys without any real scientific basis. "With every smart device, if you download a couple of apps, it claims to tell you how old you really are," says Maier. "This is very often nonsense. Everybody can say they have a new age matrix and offer it without external validation."
Furman adds that proteomic clocks, which attempt to estimate age based on the levels of thousands of proteins in the blood, remain "notoriously unreliable," even in research settings.
Maier is unsure whether the solution lies in consumer education or regulation. One possible path forward may be certification, where legitimate biological aging tests that yield reproducible and modifiable metrics are given a gold stamp by an international consortium of experts.
A Role in Preventative Medicine
Despite the current challenges, Maier remains encouraged by the underlying science and is adamant that biological aging clocks have a major role to play in preventative medicine in the coming years. "My opinion is that there's a huge opportunity to measure the health of aging individuals before diseases occur," she says. "At your age, my age, we absolutely should know how our body is functioning."
The emerging research underscores both the transformative potential of biological aging measurement and the critical need for rigorous validation, professional interpretation, and public education as these tools move toward broader clinical application.