Characteristics of the study participants (n=342) at their first chronic obstructive pulmonary disease (COPD) admission and during clinical stability*
| At first admission | During clinical stability at least 3 months after the admission | |
| Gender: female, n (%) | 24 (7.0) | – |
| Age (years), mean (SD) | 67.5 (8.5) | 67.9 (8.6) |
| Low (IV, V) socioeconomic status, n (%) | 259 (81.7) | – |
| Active workers, n (%) | 61 (17.8) | 54 (15.8) |
| Smoking status: current smoker, n (%) | 145 (42.4) | 109 (32.9) |
| Charlson index of co-morbidity (score 0–30), median (P25–P75) | 2 (1–2) | 2 (1–3) |
| Modified Medical Research Council dyspnoea scale (score 0–5), median (P25–P75) | 3 (2–4) | 2 (2–3) |
| Postbronchodilator forced expiratory volume in 1 s (% predicted), mean (SD) | 49.2 (15.7)† | 52.4 (16.2) |
| Arterial oxygen partial pressure (mm Hg), mean (SD) | 64.8 (12.0)† | 74.3 (10.6) |
| Any respiratory drug treatment, n (%) | 193 (56.4) | 288 (85.2) |
↵* Subjects were recruited during their first hospital admission because of a COPD exacerbation. The assessment of phenotype heterogeneity (through the several tests and questionnaires) was done when the patient had reached clinical stability and at least 3 months after discharge (see text for more details).
↵† Measured at hospital discharge.