Table 1.
Demographic and clinical characteristics of the study subjects*
| Current smokers (n=75) |
Former smokers (n=97) |
Never-smokers (n=165) |
P value | |
| Females, n (%) | 46 (61.3) | 43 (44.3) | 115 (69.7) | <0.001 |
| Age, years | 56±8 | 62±10 | 61±12 | <0.001 |
| BMI, kg/m2 | 26.1±4.6 | 28.1±3.9 | 27.4±5.2 | 0.023 |
| Level of studies, n (%) | 0.051 | |||
| No studies | 0 | 1 (1.0) | 2 (1.2) | |
| Primary education | 7 (9.3) | 24 (24.7) | 33 (20.0) | |
| Secondary education | 23 (30.7) | 14 (14.4) | 32 (19.4) | |
| University | 44 (58.7) | 58 (59.8) | 98 (59.4) | |
| Lives alone, n (%) | 14 (18.7) | 22 (22.7) | 22 (13.3) | 0.143 |
| Pack-years | 32±14 | 32±23 | – | 0.839 |
| Charlson Comorbidity Index | 0.3±0.7 | 0.5±1.1 | 0.3±0.8 | 0.294 |
| COTE index | 1.4±2.6 | 0.8±1.8 | 1.05±2.4 | 0.212 |
| CAT score | 9.2±6.6 | 6.8±5.4 | 6.2±5.6 | 0.001 |
| Chronic cough, n (%) | 27 (36.5) | 12 (12.5) | 18 (11.2) | <0.001 |
| Chronic bronchitis, n (%) | 10 (15.2) | 3 (3.2) | 4 (2.5) | <0.001 |
| Chronic expectoration, n (%) | 21 (28.0) | 14 (14.7) | 14 (8.5) | <0.001 |
| Dyspnoea, n (%) | 6 (8.2) | 16 (16.7) | 26 (16.5) | 0.209 |
| Wheezing, n (%) | 42 (56.8) | 27 (27.8) | 41 (24.8) | <0.001 |
| Baseline SaO2, % | 96±1 | 96±1 | 96±2 | 0.638 |
| Exhaled CO, ppm | 25±16 | 3±4 | 4±5 | <0.001 |
| Prebronchodilator FVC, z-score | 0.07±0.96 | 0.21±1.00 | 0.26±0.93 | 0.365 |
| Prebronchodilator FEV1, z-score | −0.17±1.04 | 0.05±1.09 | 0.21±1.01 | 0.031 |
| Prebronchodilator FEV1/FVC, z-score | −0.46±0.77 | −0.31±0.85 | −0.13±0.83 | 0.014 |
| Postbronchodilator FVC, z-score | 0.10+0.85 | 0.24+0.96 | 0.32+0.99 | 0.164 |
| Postbronchodilator FEV1, z-score | −0.15+0.98 | 0.06+1.11 | 0.19+1.12 | 0.011 |
| Postbronchodilator FEV1/FVC, z-score | −0.45+0.80 | −0.32–0.91 | −0.15+1.07 | 0.002 |
| 6MWD, m | 508±102 | 523±94 | 510±101 | 0.539 |
| DLCO, z-score | −0.80±0.60 | −0.30±0.71 | −0.26±0.68 | <0.001 |
| DLCO/VA, z-score | −0.10±0.12 | −0.02±0.12 | −0.01±0.15 | 0.005 |
| VA, z-score | −0.46±0.66 | −0.31±0.68 | −0.25±0.66 | 0.086 |
| Haemoglobin, g/L | 148±14 | 146±14 | 140±14 | <0.001 |
| Eosinophils, % | 2.1±1.5 | 2.3±1.6 | 2.0±1.6 | 0.440 |
| Fibrinogen, g/L | 3.9±0.8 | 3.8±0.9 | 3.8±1.0 | 0.910 |
| C reactive protein, mg/L | 1.4±2.8 | 0.9±1.5 | 1.5±2.8 | 0.134 |
| Albumin, g/l | 12.1±16.2 | 17.1±18.4 | 12.5±16.3 | 0.717 |
| BODE index | 1.0±0.5 | 1.1±0.5 | 1.1±0.6 | 0.195 |
| YPAS—physical activity summary | 55±22 | 62±24 | 57±21 | 0.236 |
| Total emphysema volume, % | 1.9±4.4 | 2.6±3.7 | 1.7±3.4 | 0.276 |
| Low density volume, % | 47±20 | 51±18 | 41±18 | 0.005 |
| P15, HU | −910±31 | −919±26 | −904±26 | 0.003 |
| Secondary bronchi WA, % | 25.4±5.7 | 25.3±5.7 | 24.5±5.4 | 0.392 |
| Pulmonary artery diameter, mm | 26±4 | 27±4 | 24±4 | 0.074 |
| Pulmonary artery:aorta ratio | 0.78±0.11 | 0.78±0.11 | 0.79±0.12 | 0.811 |
Comparison between groups using ANOVA or chi-squared test.
*Data are mean±SD or number (percentage).
ANOVA, analysis of variance; BMI, body mass index; BODE, Body Obstructive Dyspnoea Exercise; CAT, chronic obstructive pulmonary disease assessment test; CO, carbon monoxide; COTE, Chronic obstructive pulmonary disease-specific co-morbidity test; DLCO, lung diffusing capacity of carbon monoxide; FEV1, forced expiratory volume at 1 s; FVC, forced vital capacity; HU, Hounsfield units; 6MWD, 6 min walk distance; P15, 15th percentile; SaO2, oxygen saturation; VA, alveolar volume; WA, wall area; YPAS, Yale Physical Activity Survey.