Smokers are more likely to kick the habit if they are told how “old” their lungs are, a British study found on Friday.

The concept of lung age — measured by comparing a smoker’s lungs to the age of a healthy person whose lungs function the same — has helped patients better understand how smoking damages health, researchers had already found.

But that information is also effective in convincing smokers to quit, said Gary Parkes, a family physician in Hertfordshire outside London, who led the study published in the British Medical Journal.

“Telling smokers their lung age significantly improves the likelihood of them quitting smoking,” Parkes and his colleagues wrote.

The study in five general medical practices outside London involved 561 long-term smokers older than 35 and began with a simple test to record the volume and rate at which the volunteers exhaled air from the lungs.

One group received no detailed information about their results while the other people were given their lung age, shown a diagram of how smoking ages the lungs and told that quitting would slow the rate of damage.

Everyone was also strongly encouraged to quit and offered help to do so. One year later, saliva tests showed that 13 per cent of the smokers told their lung age had quit while only six per cent of people in the other group had stopped.