The app, which is being developed following a research project at the Shanghai Institutes of Biological Sciences, is hoped to assist doctors in identifying ageing lifestyle habits – such as alcohol consumption and smoking – in their patients.

To create the app, researchers at the Shanghai Institutes analysed the 3D images of 332 volunteers aged between 17 and 77 years.

By identifying facial features that change with age, such as skin texture,  the slope of the eye, and the distance between the nose and the mouth, the app's developers created a composite map which can be compared against the 3D image of a patient.

"Our study is the first to use 3D facial images to predict biological age in a human population to identify fast and slow agers," researcher Jing-Dong Han told New Scientist.

Operating solely using 3D imaging technology, the app is also the first method for comparing a person's biological and chronological age that does not require a blood or tissue sample.

To use the technology, doctors will need to have access to a smartphone, but also to a 3D camera to take photos of their patients.

Although the cost of 3D cameras is currently quite high, Han said he hoped that over time their price would fall, so his technology could  be widely used in GP clinics.

However, although it might be more convenient, not everyone is convinced that diagnosing patients based on physical appearance along is an accurate method.

Stephen Harridge of King's College London told New Scientist that he thought the app could potentially confuse skin-deep signs of ageing with the signs of an active lifestyle.

"They used a series of blood markers, such as cholesterol and albumin as markers of health, but these are very basic markers and they can tell us nothing about the amount of physical activity the subjects do, which is likely to be a key measure of health status," he said.

"This is a particularly interesting point in this study given that the more physically active people are more likely to spend time outside in conditions which might well cause more 'facial ageing' – wear and tear through exposure to the elements."