Table 1– Characteristics of the study population.
| Age years | 61.9±9.7 |
| Sex % | |
| Male | 62.9 |
| Female | 37.1 |
| BMI kg·m−2 | 24.2±5.3 |
| FEV1 % pred | 37±18.1 |
| FVC % pred | 84.5±22.4 |
| FEV1/FVC | 34.7±12.3 |
| GOLD classification % | |
| Stage I | 2.3 |
| Stage II | 17.0 |
| Stage III | 28.4 |
| Stage IV | 52.2 |
| TLC % pred | 124.9±18.4 |
| RV % pred | 205.1±58.4 |
| IC/TLC % | 26.9±8.8 |
| FRC % pred | 172.7±38.5 |
| TLCO % pred | 40.8±18 |
| PaO2 kPa | 9.4±1.4 |
| PaCO2 kPa | 5.2±0.9 |
| Arterio-alveolar oxygen gradient kPa | 5.1±1.3 |
| LTOT % | 17.1 |
| Current smokers % | 13.2 |
| Smoking history pack-years | 43.8±23 |
| Exacerbations % | |
| 0–1 per year | 39.1 |
| 2–4 per year | 42.7 |
| >4 per year | 18.2 |
Data are presented as mean±sd, unless otherwise stated. n = 604. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Obstructive Lung disease; TLC: total lung capacity; RV: residual volume; IC: inspiratory capacity; FRC: functional residual capacity; TLCO: carbon monoxide transfer factor; PaO2: arterial oxygen partial pressure; PaCO2: arterial carbon dioxide partial pressure; LTOT: long-term oxygen treatment.