Characteristics of the cohort according to country
| USA | Spain | p-value | |
| Subjects | 200 | 84 | |
| Sex M/F | 193/7 | 83/1 | 0.443 |
| Age yrs | 66 (51–79) | 67 (47–76) | 0.461 |
| BMI kg·m-2 | 27 (18–37) | 27 (19–36) | 0.658 |
| 6MWD m | 350 (146–503) | 463 (336–635) | <0.001 |
| FEV1 L | 1.20 (0.6–2.1) | 1.15 (0.6–2.3) | 0.946 |
| FEV1 % pred | 37 (19–67) | 43 (21–75) | 0.014 |
| IC/TLC | 0.29 (0.14–0.42) | 0.28 (0.13–0.44) | 0.385 |
| Charlson index | 4 (2–8) | 2 (1–6) | <0.001 |
Data are presented as n or median (5th–95th percentile). M: male; F: female; BMI: body mass index; 6MWD: 6-min walking distance; FEV1: forced expiratory volume in one second; % pred: % predicted; IC: inspiratory capacity; TLC: total lung capacity.