Prevalence of chronic obstructive pulmonary disease (COPD) and respiratory symptoms
| Lowlands | Highlands | p-value | |
| Subjects | 193 | 199 | |
| Post-BD FVC % pred | 92.0 (84.0–104.0) | 100.0 (92.0–110.0) | <0.001 |
| Post-BD FEV1 % pred | 90.0 (83.0–101.5) | 92.0 (85.0–104.0) | 0.091 |
| Post-BD FEV1/FVC % | 82.0 (75.0–96.0) | 76.0 (65.0–97.0) | 0.003 |
| COPD | 20 (10.4) | 73 (36.7) | <0.001 |
| Male | 16 (80.0) | 36 (49.3) | <0.001 |
| Moderate/severe (GOLD stage ≥2) | 14 (70.0) | 18 (24.7) | <0.001 |
| SpO2 % | 95.0 (95.0–96.0) | 93.0 (92.0–95.0) | <0.001 |
| Chronic cough/sputum# | 15 (7.8) | 47 (23.6) | <0.001 |
| Severe breathlessness (MRC dyspnoea scale ≥4) | 6 (3.1) | 22 (11.1) | 0.003 |
Data are presented as n, median (interquartile range) or n (%). Missing outcomes for lung function were excluded from the study (figure 1); there were no other missing values. BD: bronchodilation; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s; GOLD: Global Initiative for Chronic Obstructive Lung Disease; SpO2: arterial oxygen saturation measured by pulse oximetry; MRC: Medical Research Council. #: chronic is defined as having symptoms for ≥2 months.