People who age well are often asked what their secret is. But new research could reduce the need for guesswork - and usher in an era of ageing tests.

A team of academics from Israel, Britain, America and New Zealand has just concluded that some young adults are ageing three times faster than others. It did so by testing their "biological age" and comparing it to their actual age.

While they found that, for example, a person of 38 could be as young, biologically-speaking, as 30, by the same criteria he or she could also be almost 60.

"We reached these ages by measuring a number of different biomarkers, including blood pressure, cholesterol, lung function, telomeres [the caps at the end of each strand of DNA] and others," explained Salomon Israel of Hebrew University, a co-author of the study.

He stressed that the research was important because, while studies on ageing normally focus on animals, or on humans who are 50-plus, this one shows how biological ages vary even among the young.

Ageing, he said, is a process of decline in the functioning of many organ systems simultaneously, and the research indicates that the process can be well under way among young adults who are decades away from developing age-related diseases. "The research allows us to quantify the ageing process of people who are still young," he said.

Dr Israel foresees a time when people undergo regular ageing tests. "We'd have a way to measure biological age and be able to say, 'you're ageing faster than your peers, or slower.'"

Doctors will be able to base their decisions about patients on that basis. "We can use this tool to establish how well different interventions work," he said.

The participants in the study were New Zealanders born in 1972 and 1973. The group of 1,037 people spanned the socioeconomic spectrum and health categories of the general population.