Prevalence and correlates of pulmonary emphysema in smokers and former smokers. A densitometric study of participants in the ITALUNG trial

Abstract

We assessed with computed tomography (CT) densitometry the prevalence of emphysema in 266 (175 men and 91 women; mean age 64 +/- 4 years) smokers and former smokers enrolled in the ITALUNG trial of lung cancer screening with low-dose thin-slice CT. Whole-lung volume and the relative area at -950 Hounsfield units (RA(950)) and mean lung attenuation (MLA) in 1 of every 10 slices (mean, 24 slices per subject) were measured. Lung volume, MLA and RA950 significantly correlated each other and with age. Average RA950 >6.8% qualifying for emphysema was present in 71 (26.6%) of 266 subjects, with a higher prevalence in men than in women (30.3% vs 19.8%; p = 0.003). Only in smokers was a weak (r = 0.18; p = 0.05) correlation between RA950 and packs/year observed. In multiple regression analysis, the variability of RA950 (R2 = 0.24) or MLA (R2 = 0.34) was significantly, but weakly explained by age, lung volume and packs/year. Other factors besides smoking may also have a significant role in the etiopathogenesis of pulmonary emphysema.

Factors influencing the decline in lung density in a Danish lung cancer screening cohort

“…These opposing effects of smoking are not surprising, and are probably explained by smoking induced inflammation with increased movement of plasma and inflammatory cells from the circulation into the lung interstitium in the short-term and in the long-term remodelling and loss of lung tissue. The opposing effects of smoking on lung density may also explain the inconsistent results of previous cross-sectional studies [7][8][9]. In order to avoid large inter-individual variations, CT-measurements of participants who changed their smoking habits were excluded from the date of change.…”

“…Measurement of lung density by computed tomography (CT) is a surrogate marker for emphysema and reflects both disease severity [2][3][4] and physiological impairment [5][6]. Crosssectional studies of the influence of smoking on lung density by CT have reported inconsistent results, with some researchers finding no influence of smoking habit on lung density [7], while others report decreased lung density with increasing pack-yrs [8][9]. This is not surprising given the fact that smoking has opposing effects on lung density.…”

Progress in Imaging COPD, 2004 - 2014

“…39 Several authors have shown that current smokers appear to have lower levels of emphysema than former smokers. 40,41 Even more intriguingly, the extent of emphysema appears to increase quite rapidly following smoking cessation, reflecting a fall in lung attenuation. 42,43 This effect is presumed to be due to a smoking-induced increase in inflammatory cells in the lung in current smokers, resulting in increased lung attenuation, so that partial volume averaging masks the areas of low-attenuation emphysema.…”

Lung densitometry: why, how and when

“…Since, detection of mild emphysema is difficult on chest X-rays (14), lung CT has become the preferred tool to establish presence and severity of pulmonary emphysema in the single subject with no or mild symptoms and in cohorts of subjects at variable risk defined according to different criteria, typically smoking history and age (34,37,56,101). For such a purpose, visual score and densitometry can be applied.…”