Characteristics of included and excluded participants
| Included participants | Excluded participants* | ||||
| 1995 | 1996 | 2001 | Total | ||
| n | 7071 | 7565 | 6468 | 21 104 | 6549 |
| Males | 3303 (46.7%) | 3551 (46.9%) | 2993 (46.3%) | 9847 (46.7%) | 2616 (40.0%) |
| Mean age, years (SD) | 58.4 (12.3) | 58.1 (12.3) | 57.9 (11.9) | 58.1 (12.2) | 63.9 (14.3) |
| Age group | |||||
| 40–49 | 2129 (30.1%) | 2409 (31.8%) | 1872 (28.9%) | 6410 (30.4%) | 1389 (21.2%) |
| 50–59 | 1812 (25.6%) | 1876 (24.8%) | 1954 (30.2%) | 5642 (26.7%) | 1290 (19.7%) |
| 60–69 | 1598 (22.6%) | 1695 (22.4%) | 1380 (21.3%) | 4673 (22.1%) | 1317 (20.1%) |
| 70–79 | 1158 (16.4%) | 1186 (15.7%) | 969 (15.0%) | 3313 (15.7%) | 1418 (21.7%) |
| 80+ | 374 (5.3%) | 399 (5.3%) | 293 (4.5%) | 1066 (5.1%) | 1135 (17.3%) |
| Socioeconomic status† | |||||
| Non-manual occupations | 3928 (56.4%) | 4195 (56.2%) | 3683 (57.8%) | 11 806 (56.7%) | 3117 (49.6%) |
| Manual occupations | 3028 (43.4%) | 3254 (43.6%) | 2676 (42.0%) | 8958 (43.1%) | 3158 (50.2%) |
| Other | 14 (0.2%) | 17 (0.2%) | 13 (0.2%) | 44 (0.2%) | 13 (0.2%) |
| Smoking status† | |||||
| Current | 1612 (22.8%) | 1806 (23.9%) | 1327 (20.5%) | 4745 (22.5%) | 1536 (23.5%) |
| Ex-regular | 2569 (36.4%) | 2637 (34.9%) | 2290 (35.4%) | 7496 (35.5%) | 2237 (34.2%) |
| Never regular | 2887 (40.9%) | 3122 (41.3%) | 2850 (44.1%) | 8859 (42.0%) | 2775 (42.4%) |
| Pack years smoked | |||||
| 0 | 3107 (44.0%) | 3359 (44.4%) | 3038 (47.0%) | 9504 (45.0%) | 2973 (45.4%) |
| 1–19 | 1817 (25.7%) | 1922 (25.4%) | 1656 (25.6%) | 5395 (25.6%) | 1517 (23.2%) |
| 20–49 | 1695 (24.0%) | 1803 (23.8%) | 1389 (21.5%) | 4887 (23.2%) | 1552 (23.7%) |
| 50+ | 449 (6.4%) | 481 (6.4%) | 384 (5.9%) | 1314 (6.2%) | 506 (7.7%) |
| Exposure to passive smoking, h | |||||
| Mean hours per week (SD) | 9.2 (18.4) | 9.3 (18.3) | 6.1 (13.8) | 8.3 (17.1) | 7.0 (16.3) |
| Median hours per week (IQR) | 2 (0–8) | 2 (0–8) | 1 (0–5) | 1 (0–7) | 0 (0–5) |
| 0 | 2859 (40.5%) | 3111 (41.2%) | 3167 (49.1%) | 9137 (43.4%) | 3425 (52.6%) |
| 1–9 | 2540 (36.0%) | 2665 (35.3%) | 2193 (34.0%) | 7398 (35.1%) | 1883 (28.9%) |
| 10–19 | 667 (7.9%) | 560 (7.4%) | 440 (6.8%) | 1557 (7.4%) | 425 (6.5%) |
| 20+ | 1105 (15.7%) | 1224 (16.2%) | 657 (10.2%) | 2986 (14.2%) | 778 (12.0%) |
| Any respiratory symptoms‡ | 3120 (44.1%) | 3340 (44.2%) | – | 6460 (44.1%) | 1823 (47.7%) |
| Physician-diagnosed asthma | 692 (9.8%) | 794 (10.5%) | 801 (12.4%) | 2287 (10.8%) | 702 (10.7%) |
| COPD§ | |||||
| LLN | 675 (10.6%) | 593 (8.8%) | 414 (7.3%) | 1682 (8.9%) | – |
| GOLD | 1190 (18.7%) | 1086 (16.1%) | 757 (13.4%) | 3033 (16.1%) | – |
| NICE | 526 (8.3%) | 443 (6.6%) | 333 (5.9%) | 1302 (6.9%) | – |
↵* Excluded due to invalid lung function or height measurements.
↵† Missing data: 557/27 653 (2.0%) had missing socioeconomic status and 5/27 653 (0.02%) missing smoking history.
↵‡ Dyspnoea, wheeze, chronic cough or phlegm. Not recorded in 2001.
↵§ Among those without asthma: GOLD criteria26: FEV1/FVC ratio <0.7; NICE criteria: FEV1/FVC<0.7 and FEV1<80% predicted (equivalent to GOLD stage II)27; lower limit of normal (LLN) criteria24 25: participants with FEV1/FVC values >1.645 SD below the mean reference value.
COPD, chronic obstructive pulmonary disease.