| COPD patients with ≥3 annual measurements | COPD patients with <3 annual measurements | p-value | |
| Subjects | 704 | 447 | |
| Male/female | 652/52 | 406/41 | 0.334 |
| Age years | 66±9 | 67±9 | 0.103 |
| Smoking pack-years | 66±26 | 70±28 | 0.393 |
| Active smoking % | 29 | 38 | 0.004 |
| BMI kg·m−2 | 27±5.6 | 26.9±6.2 | 0.551 |
| FEV1 L | 1.41±0.56 | 1.39±0.65 | 0.467 |
| FEV1 % | 46±17 | 46±20 | 0.969 |
| PaO2 mmHg | 72.7±11.9 | 69.6±14.7 | <0.001 |
| FVC % | 72±21 | 70±20 | 0.705 |
| 6MWD m | 372±127 | 329±154 | <0.001 |
| mMRC dyspnoea score | 2 (0–4) | 2 (1–4) | 0.015 |
| BODE index | 3 (0–8) | 4 (0–9) | 0.002 |
| IC/TLC ratio | 0.30±0.12 | 0.29±0.11 | 0.958 |
| KCO % | 60±23 | 58±21 | 0.702 |
| Charlson index | 4 (2–9) | 4 (0–11) | 0.987 |
| Hospitalisations per patient per year | 0.21±0.02 | 0.41±0.04 | <0.001 |
| Inhaled anticholinergic % | 68 | 62 | 0.109 |
| Inhaled β2-agonist % | 92 | 86 | 0.003 |
| Inhaled corticosteroid % | 62 | 48 | <0.001 |
| SGRQ | 47±22 | 50±22 | 0.167 |
Data presented as n, mean±sd or median (5–95th percentile). COPD: chronic obstructive pulmonary disease; BMI: body mass index; FEV1: forced expiratory volume in 1 s; PaO2: arterial oxygen tension; FVC: forced vital capacity; 6MWD: 6-min walk distance; mMRC: modified Medical Research Council; BODE: BMI, airflow obstruction, dyspnoea, exercise capacity; IC: inspiratory capacity; TLC: total lung capacity; KCO: transfer coefficient of the lung for carbon monoxide; SGRQ: St George’s Respiratory Questionnaire.