Using spirometry to calculate patients' 'lung age' is a powerful motivator to stop smoking.

The study recruited 561 smokers aged >35 years from five practices in Hertfordshire. Participants had their FEV₁ determined using spirometry and were randomised to receive the results either as a raw FEV₁ figure or as their 'lung age'. FEV₁ normally declines with age, so mapping the patient's result on a graph and comparing it with the FEV₁ for a healthy non-smoker can derive the 'lung age' of the patient (see table 1, below, and the attached graph).

41185132The study found that patients who had been told their 'lung age' rather than the raw FEV₁ figure were twice as likely to quit smoking - 13.6% of patients in the 'lung age' group compared with 6.4% of controls (P=0.005).

There was no evidence that patients with worse 'lung ages' were more likely to quit than those with normal lung function. However, the study was of insufficient power to investigate this relationship. The authors comment that some of the patients were relieved their 'lung age' was normal and felt it wasn't too late to quit.

The study also showed the beneficial effects of screening smokers aged >35 years. Around 7% of the study population were known to suffer from COPD. Spirometry identified a further 17.4% in the control group and 14.3% in the study group with this condition.

The authors suggest that routine spirometry screening would be beneficial and should be included in the GP contract. Such a measure would allow more targeted smoking cessation advice and medical treatment to be started earlier, perhaps delaying disease progression.

Other studies have shown that making patients aware of such 'biomarkers' can be effective in encouraging smoking cessation.

'Lung age' seems a particularly vivid and useful concept.

Parkes G, Greenhalgh T, Griffin M et al. Effect on smoking quit rate of telling patients their lung age: the Step2quit randomised controlled trial. BMJ 2008;336:598-600