It's easy to know your chronological age, as it's just the amount of time that has elapsed since you were born. However, what about your biological age – the amount that your body has physically aged, which varies from person to person? Well, according to a new study out of China, a simple urine test could tell you.

Knowing your biological age is potentially quite important, as it can be used to determine your risk of developing age-related diseases, or even your risk of death. Additionally, it's crucial to know test subjects' biological age when developing anti-aging drugs.

In a previous study on mice, rats and monkeys, the scientists found that levels of a biomarker known as 8-oxo-7,8-dihydroguanosine (or 8-oxoGsn, for short) increased in urine samples as the animals got older. The biomarker is produced by the oxidation of RNA (ribonucleic acid), a process which in turn is associated with biological aging.

"Oxygen by-products produced during normal metabolism can cause oxidative damage to biomolecules in cells, such as DNA and RNA," says Jian-Ping Cai, from the Beijing-based National Center of Gerontology. "As we age, we suffer increasing oxidative damage, and so the levels of oxidative markers increase in our body."

In the new study, the researchers wanted to see if the same thing applied to human urine. Utilizing a rapid analysis technique called ultra-high-performance liquid chromatography, they analyzed samples collected from 1,228 people aged 2 to 90 years old. Sure enough, in individuals aged 21 and older, there was an age-dependent increase in urinary 8-oxoGsn.

According to Cai, this finding makes the biomarker promising as a reliable indicator of biological age.

The research, which also involved scientists from Sichuan University, is described in a paper that was recently published in the journal Frontiers in Aging Neuroscience.