title: Evolution of emphysema in relation to smoking.
abstract: OBJECTIVE
  We have little knowledge about the evolution of emphysema, and relatively little is understood about its evolution in relation to smoking habits. This study aims to assess the evolution of emphysema in asymptomatic current and former smokers over 2 years and to investigate the association with subjects' characteristics. The study was approved by our Ethics Committee and all participants provided written informed consent.
  
  
  METHODS
  We measured emphysema by automatic low-dose computed tomography densitometry in 254 current and 282 former smokers enrolled in a lung-cancer screening. The measures were repeated after 2 years. The association between subjects' characteristics, smoking habits and emphysema were assessed by chi-squared and Wilcoxon tests. Univariate and multivariate odds ratios (OR) with 95% confidence intervals (CI) were calculated for the risk of emphysema worsening according to subjects' characteristics. We assessed the trend of increasing risk of emphysema progression by smoking habits using the Mantel-Haenszel chi-squared test.
  
  
  RESULTS
  The median percentage increase in emphysema over a 2-year period was significantly higher in current than in former smokers (OR 1.8; 95% CI 1.3-2.6; p < 0.0001). The risk of worsening emphysema (by 30% in 2 years) in current smokers increased with smoking duration (p for trend <0.02).
  
  
  CONCLUSIONS
  As emphysema is a known risk factor for lung cancer, its evaluation could be used as a potential factor for identification of a high-risk population. The evaluation of emphysema progression can be added to low-dose CT screening programmes to inform and incite participants to stop smoking.
authors.affiliation: Department of Radiology, European Institute of Oncology, via Ripamonti 435, Milan, Italy. massimo.bellomi@ieo.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellomi
authors.forename: Cristiano
authors.initials: C
authors.lastname: Rampinelli
authors.forename: Giulia
authors.initials: G
authors.lastname: Veronesi
authors.forename: Sergio
authors.initials: S
authors.lastname: Harari
authors.forename: Federica
authors.initials: F
authors.lastname: Lanfranchi
authors.forename: Sara
authors.initials: S
authors.lastname: Raimondi
authors.forename: Patrick
authors.initials: P
authors.lastname: Maisonneuve
mesh_terms: D015502:Absorptiometry, Photon / Q000706:statistics & numerical data*; D000368:Aged; D000369:Aged, 80 and over; D015984:Causality; D015897:Comorbidity; D005260:Female; D006801:Humans; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D018570:Risk Assessment; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*
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