Distribution of characteristics in 11 398 observation periods (generated by 8646 unique individuals) across stages of chronic obstructive pulmonary disease (COPD) according to Global Initiative for Chronic Obstructive Lung Disease guidelines
| Normal | COPD | |||
| Stage I | Stage II | Stage III/IV | ||
| Observation periods | 77.8 (8869) | 9.2 (1051) | 10.8 (1226) | 2.2 (252) |
| Male | 41.4 (3323) | 48.9 (549) | 49.7 (722) | 57 (156) |
| Age years | 63.0±9.5 | 67.7±9.2 | 67.8±8.4 | 69.3±7.6 |
| FEV1 L | 2.7±0.7 | 2.6±0.7 | 1.9±0.5 | 1.1±0.3 |
| FVC L | 3.6±1.0 | 3.9±1.0 | 3.1±0.8 | 2.3±0.7 |
| FEV1/FVC % | 76.6±4.0 | 66.4±3.5 | 62.6±6.0 | 49.9±10.1 |
| FEV1 % predicted | 93.5±14.2 | 91.3±9.5 | 67.5±8.3 | 40.2±8.4 |
| Dyspnoea# | 2.8 (146) | 3.9 (31) | 5.9 (61) | 19.5 (38) |
| Daily cough | 16.7 (917) | 21.6 (183) | 31.0 (342) | 49.2 (102) |
| BMI kg·m−2 | 27.3±4.1 | 25.5±3.7 | 26.2±4.2 | 26.1±4.2 |
| Smoking | ||||
| Current | 18.0 (1582) | 29.6 (308) | 41.7 (501) | 47.2 (119) |
| Former | 42.7 (3784) | 47.7 (499) | 42.2 (518) | 39.7 (100) |
| Pack-years current | 19.7±12.6 | 21.5±12.7 | 23.5±14.8 | 26.0±16.1 |
| Pack-years former | 12.7±12.6 | 16.6±15.9 | 19.5±15.9 | 27.7±18.3 |
| History of cancer | 7.7 (616) | 10.5 (118) | 10.0 (145) | 13.9 (38) |
| History of CVD | 13.6 (1092) | 16.5 (185) | 24.4 (354) | 28.2 (77) |
| Diabetes | 5.3 (307) | 3.76 (34) | 5.1 (59) | 6.2 (14) |
Data are presented as mean±sd or % (n). COPD stages III and IV are combined. FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; BMI: body mass index; CVD: cardiovascular disease. #: dyspnoea when walking calmly.