Baseline socio-demographic and clinical characteristics of the cohort
| Variable | COPD (n=406) | Non-COPD (n=3320) | p-value |
| Male gender | 186 (45.8) | 1526 (46.0) | 0.954 |
| Age years | 67.0 (59–73) | 63.0 (57–70) | <0.001 |
| Marital status | <0.001 | ||
| Single/separated/widowed | 153 (37.7) | 938 (28.3) | |
| Living in a relationship | 253 (62.3) | 2382 (71.7) | |
| Ethnicity | |||
| White | 395 (97.3) | 3272 (98.6) | 0.054 |
| Socio-economic class | <0.001 | ||
| Managerial and professional | 108 (26.6) | 1209 (36.4) | |
| Intermediate | 53 (13.1) | 467 (14.1) | |
| Small employers and own-account workers | 44 (10.8) | 388 (11.7) | |
| Lower supervisory and technical | 50 (12.3) | 329 (9.9) | |
| Semi-routine occupations | 144 (35.5) | 899 (27.1) | |
| Other | 7 (1.7) | 28 (0.8) | |
| Self-reported health | <0.001 | ||
| Excellent | 36 (8.9) | 577 (17.4) | |
| Very good | 99 (24.4) | 1140 (34.3) | |
| Good | 144 (35.5) | 1071 (32.3) | |
| Fair | 93 (22.9) | 438 (13.2) | |
| Poor | 34 (8.4) | 94 (2.8) | |
| Physical activity | <0.001 | ||
| None | 25 (6.2) | 118 (3.6) | |
| Mild | 64 (15.8) | 373 (11.2) | |
| Moderate | 236 (58.1) | 1684 (50.7) | |
| Vigorous | 81 (20.0) | 1145 (34.5) | |
| Dyspnoea | <0.001 | ||
| Grade 0 | 172 (42.4) | 2519 (75.9) | |
| Grade 1 | 151 (37.2) | 549 (16.5) | |
| Grade 2 | 34 (8.4) | 90 (2.7) | |
| Grade 3 | 49 (12.1) | 162 (4.9) | |
| Smoking status | <0.001 | ||
| Never smoker | 100 (24.6) | 1346 (40.5) | |
| Former smoker | 160 (39.4) | 1518 (45.7) | |
| Current smoker | 146 (36.0) | 456 (13.7) | |
| Spirometry measurements | |||
| FEV1 L | 1.7 (1.1–2.3) | 2.5 (2.0–3.1) | <0.001 |
| FVC L | 3.1 (2.3–3.8) | 3.2 (2.6–4.0) | 0.001 |
| PEF L·min−1 | 286.5 (202.8–378.8) | 385 (307.0–493.0) | <0.001 |
| FEV1 % pred | 70.2 (49.5–84.6) | 94.0 (83.5–104.8) | <0.001 |
| FVC % pred | 92.2 (78.0–107.2) | 94.4 (83.6–106.0) | 0.056 |
Data are presented as n (%) or median (IQR). p-Values in bold are statistically significant. COPD: chronic obstructive pulmonary disease; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; PEF: peak expiratory flow; IQR: interquartile range (25th to 75th percentile).