Scientists have found that changes in a person’s “biological age” over time may be a better way to predict future health and survival than a single test.

The research focused on epigenetic clocks, which estimate how quickly a person’s body is aging. Unlike your chronological age, the number of birthdays you’ve had, biological age looks at changes inside your cells that may reflect your overall health.

Researchers have long known that these aging clocks can help estimate the risk of disease and early death. However, one test taken at a single point in time does not tell the whole story.

In a new study, researchers followed 699 adults in Italy for as long as 24 years. They found that people whose biological age increased more rapidly over time were more likely to die earlier than those whose biological aging stayed more stable.

The findings suggest that repeated testing may be much more useful than relying on a single measurement. Watching how biological age changes over several years could provide a clearer picture of a person’s health and how quickly they are aging.

Scientists say this is especially important as new treatments aimed at slowing aging are developed. If biological age changes in response to healthier habits or new therapies, these tests could help show whether those approaches are actually working.

The researchers caution that more studies are needed before epigenetic clocks become part of routine medical care. Scientists still have much to learn about what these tests measure and how they respond to different lifestyle changes and treatments.

Even so, the new findings add to growing evidence that tracking biological aging over time may one day become an important tool for helping people stay healthier as they grow older.