Intended for healthcare professionals


Effect on smoking quit rate of telling patients their lung age: the Step2quit randomised controlled trial

BMJ 2008; 336 doi: (Published 13 March 2008) Cite this as: BMJ 2008;336:598
  1. Gary Parkes, general practitioner1,
  2. Trisha Greenhalgh, professor 2,
  3. Mark Griffin, lecturer in medical statistics2,
  4. Richard Dent, consultant chest physician department of chest medicine3
  1. 1The Limes Surgery, Hoddesdon, Hertfordshire EN11 8EP
  2. 2Department of Primary Care and Population Sciences, University College London, London N19 5LW
  3. 3Queen Elizabeth II Hospital, Welwyn Garden City, Hertfordshire AL7 4HQ
  1. Correspondence to: G Parkes Parkesko{at}
  • Accepted 30 January 2008


Objective To evaluate the impact of telling patients their estimated spirometric lung age as an incentive to quit smoking.

Design Randomised controlled trial.

Setting Five general practices in Hertfordshire, England.

Participants 561 current smokers aged over 35.

Intervention All participants were offered spirometric assessment of lung function. Participants in intervention group received their results in terms of “lung age” (the age of the average healthy individual who would perform similar to them on spirometry). Those in the control group received a raw figure for forced expiratory volume at one second (FEV1). Both groups were advised to quit and offered referral to local NHS smoking cessation services.

Main outcome measures The primary outcome measure was verified cessation of smoking by salivary cotinine testing 12 months after recruitment. Secondary outcomes were reported changes in daily consumption of cigarettes and identification of new diagnoses of chronic obstructive lung disease.

Results Follow-up was 89%. Independently verified quit rates at 12 months in the intervention and control groups, respectively, were 13.6% and 6.4% (difference 7.2%, P=0.005, 95% confidence interval 2.2% to 12.1%; number needed to treat 14). People with worse spirometric lung age were no more likely to have quit than those with normal lung age in either group. Cost per successful quitter was estimated at £280 (€366, $556). A new diagnosis of obstructive lung disease was made in 17% in the intervention group and 14% in the control group; a total of 16% (89/561) of participants.

Conclusion Telling smokers their lung age significantly improves the likelihood of them quitting smoking, but the mechanism by which this intervention achieves its effect is unclear.

Trial registration National Research Register N0096173751.


  • We thank Liane Andrews (healthcare assistant) and members of the practice based steering group of nurses, manager, and lay members. We also thank the doctors and staff of the five local general practice surgeries for their help and cooperation. We thank P W Jones for permission to use the St George’s respiratory questionnaire and for supplying copies of the questionnaire and the electronic scoring tool.

  • Contributors: All authors made a substantial contribution to: conception and design, or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content, and final approval of the version to be published. GP conceived, designed, and piloted the original study. The work formed part of a research PhD thesis at University College London, with TG and RD as supervisors. MG supplied statistical advice and analysis and wrote the statistical section. GP is guarantor.

  • Funding: Leading practice through research award from the Health Foundation.

  • Competing interests: None declared.

  • Ethical approval: Hertfordshire local research ethics committee (application number EC03718) and West Essex local research ethics committee (1608-0104).

  • Provenance and peer review: Not commissioned; externally peer reviewed.

View Full Text