A ground breaking New Zealand study has discovered ways to measure a person's true biological age.

The Otago University research followed a 1000 people over 40 years, discovering a person's chronological age doesn't always correlate with their biological age. Otago University's Director of Genetics Peter Dearden has been working on the project.

"They ring around every couple of years and they assess a whole load of measures of their health and their mental health and then they take biological measurements as well. It's those measurements that have been critical for measuring biological ageing."

He admits it's no surprise that people often seem older or younger than they are, but having biological measures means they can start to understand what influences the way people age.

Dearden is hopeful this kind of information will open the way for accurate testing of anti-ageing treatments.

"This paper provides a breakthrough whereby we can measure ageing and if we can measure ageing we can then say, well it would be good if we got this particular treatment we could try, and does that actually have an effect or not."

The study uses a range of measures from blood pressure to white blood cell count, liver and kidney function.