Clinical and functional characteristics of all smokers, smokers without COPD (noCOPD) and with COPD (COPD)
| All smokers | NoCOPD | COPD | p-value | |
| Subjects n | 511 | 209 | 302 | |
| Male | 423 (83) | 147 (70) | 276 (91) | 0.001 |
| Age years | 58±10 | 52±11 | 62±8 | 0.001 |
| Smoking history pack-years | 43±24 | 35±19 | 49±25 | 0.001 |
| FEV1 post-bronchodilator L | 2.34±0.85 | 2.88±0.78 | 1.96±0.67 | 0.001 |
| FEV1 post-bronchodilator (% pred) | 79±22 | 95±5 | 68±19 | 0.001 |
| FEV1/FVC post-bronchodilator % | 64±15 | 78±5 | 54±11 | 0.001 |
| MMEF 25–75 post-bronchodilator % pred | 47±29 | 75±21 | 27± 3 | 0.001 |
| DLCO % pred | 80±21 | 86±17 | 76±22 | 0.0001 |
| Decline of FEV1 per year mL year−1 | 32±46 | 33±37 | 31±52 | ns |
| Subjects with chronic bronchitis | 193 (38) | 56 (27) | 137 (45) | 0.001 |
| Subjects with mMRC ≥2 | 214 (42) | 71 (34) | 143 (47) | 0.006 |
| mMRC score | 1.33±0.70 | 1.10±1.19 | 1.50±1.09 | 0.0001 |
| CAT score | 9.7±7.3 | 9.0±6.9 | 10.2±7.1 | 0.042 |
| Distance at 6 min walk test m | 419±122 | 481±114 | 376±109 | 0.001 |
| Number of total exacerbations per year | 0.79±1.54 | 0.49±1.05 | 1.00±1.78 | 0.001 |
| Number of severe exacerbations per year | 0.05±0.14 | 0.03±0.09 | 0.06±0.17 | 0.024 |
| Subjects who developed comorbidities | 418 (82) | 160 (77) | 258 (85) | 0.001 |
| GOLD 1 | 81 (27) | |||
| GOLD 2 | 169 (56) | |||
| GOLD 3–4 | 52 (17) |
Data are presented as number (%) or mean±sd. p-value refers to Mann–Whitney test or χ2 test, for comparisons between noCOPD and COPD. ns: nonsignificant; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; MMEF: maximum mid-expiratory flow at 25–75% of FVC; CAT: COPD Assessment Test; mMRC: modified Medical Research Council; GOLD: Global Initiative for Chronic Obstructive Lung Disease.