Characteristics of the included patients
| 1995 | 1996 | 2001 | All | |
| N | 6379 | 6771 | 5667 | 18 817 |
| Men (n (%)) | 3033 (47.6) | 3197 (47.3) | 2662 (47.0) | 8892 (47.3) |
| Age (years) (mean (SD)) | 58.4 (12.3) | 58.1 (12.3) | 58.0 (12.0) | 58.1 (12.2) |
| Age group (years) (n (%)) | ||||
| 40–49 | 1916 (31.0) | 2168 (32.0) | 1634 (28.8) | 5718 (30.4) |
| 50–59 | 1635 (25.6) | 1677 (24.8) | 1705 (30.1) | 5017 (26.7) |
| 60–69 | 1437 (22.5) | 1504 (22.2) | 1196 (21.1) | 4137 (22.0) |
| 70–79 | 1047 (16.4) | 1056 (15.6) | 868 (15.3) | 2971 (15.8) |
| 80+ | 344 (5.4) | 366 (5.4) | 264 (4.7) | 974 (5.2) |
| Smoking status (n (%)) | ||||
| Never regular | 2635 (41.3) | 2811 (41.5) | 2505 (44.2) | 7951 (42.3) |
| Ex-regular | 2287 (35.9) | 2327 (34.4) | 1990 (35.1) | 6604 (35.1) |
| Current | 1455 (22.8) | 1633 (24.1) | 1171 (20.7) | 4259 (22.6) |
| Not reported | 2 (0.03) | 0 | 1 (0.02) | 3 (0.02) |
| Pack years smoked (n (%)) | ||||
| 0 | 2835 (44.5) | 3034 (44.8) | 2675 (47.2) | 8544 (45.4) |
| 1–19 | 1613 (25.3) | 1697 (25.1) | 1440 (25.4) | 4750 (25.3) |
| 20–49 | 1522 (23.9) | 1627 (24.0) | 1220 (21.5) | 4369 (23.2) |
| 50+ | 407 (6.4) | 407 (6.4) | 331 (5.9) | 1151 (6.1) |
| Socioeconomic status/occupation (n (%)) | ||||
| Non-manual occupation | 3545 (55.6) | 3759 (55.5) | 3221 (56.8) | 10 525 (55.9) |
| Manual occupation | 2732 (42.8) | 2903 (42.9) | 2349 (41.5) | 7984 (42.4) |
| Other | 13 (0.2) | 16 (0.2) | 12 (0.2) | 41 (0.2) |
| Not reported | 89 (1.4) | 93 (1.4) | 85 (1.5) | 267 (1.4) |
| Diagnosed conditions (n (%)) | ||||
| Any longstanding illness | 3085 (48.4) | 3304 (48.8) | 2852 (50.3) | 9341 (49.6) |
| Respiratory conditions | 287 (4.5) | 268 (4.0) | 175 (3.1) | 730 (3.9) |
| Bronchitis/emphysema | 81 (1.3) | 88 (1.3) | 39 (0.7) | 208 (1.1) |
| COPD* (n (%)) | ||||
| GOLD | 1190 (18.7) | 1087 (16.1) | 758 (13.4) | 3035 (16.1) |
| NICE | 526 (8.3) | 444 (6.6) | 334 (5.9) | 1304 (7.0) |
| LLN | 675 (10.6) | 594 (8.8) | 415 (7.3) | 1684 (9.0) |
↵* Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria18: FEV1/FVC ratio <0.7; National Institute for Health and Clinical Excellence (NICE) criteria: FEV1/FVC <0.7 and FEV1 <80% predicted (equivalent to GOLD stage II)19; lower limit of normal (LLN) criteria20 ,21: participants with FEV1/FVC values >1.645 SD below the mean reference value.
COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity.