Background The effect of smoking cessation and smoking relapse on lung density was studied using low-dose CT.
Methods Spiral, multidetector, low-dose CT was performed on 726 current and former smokers (>20 pack-years) recruited from a cancer screening trial. Lung density was quantified by calculating the 15th percentile density (PD15), which was adjusted to predicted total lung capacity. Data were analysed by linear regression models.
Results At baseline mean PD15 was 45 g/l in former smokers (n=178) and 55 g/l in current smokers (n=548), representing a difference of 10 g/l (p<0.001). After smoking cessation (n=77) PD15 decreased by 6.2 g/l (p<0.001) in the first year, and by a further 3.6 g/l (p<0.001) in the second year, after which no further change could be detected. Moreover, the first year after relapse to smoking (n=18) PD15 increased by 3.7 g/l (p=0.02).
Conclusions Current smoking status has a major influence on lung density assessed by CT, and the difference in lung density between current and former smokers observed in cross-sectional studies corresponds closely to the change in lung density seen in the years after smoking cessation. Current smoking status, and time since cessation or relapse, should be taken into account when assessing the severity of diseases such as emphysema by CT lung density.
- imaging/CT MRI, etc
- pulmonary emphysema
- smoking cessation
- tobacco and the lung
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Funding The Danish Lung Cancer Screening Trial receives financial support from the Danish Ministry of Interior and Health. The densitometric measurements reported in this paper were supported by unrestricted grants from the Danish Council for Strategic Research under the Programme Commission for Nanoscience and Technology, Biotechnology and IT (NABIIT) and from AstraZeneca R&D, Sweden.
Competing interests MD has been employed at AstraZeneca in the past 5 years, and AstraZeneca has sponsored this study by unrestricted grants. MD holds stocks from AstraZeneca, as part of AstraZeneca bonus programme. The remaining authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Ethics approval The Danish lung cancer screening trial was approved by the ethical committee of Copenhagen County on 31 January 2003. Approval of data management in the trial was obtained from the Danish Data Protection Agency on 11 February 2005.
Provenance and peer review Not commissioned; externally peer reviewed.