Baseline characteristics of subjects completing the screening questionnaire(SQ), the main questionnaire (MQ) and pulmonary function tests (PFTs) to illustrate possible differences in subject characteristics by various phases of the study programme
| SQ | MQ | PFTs | |
| Sex male | 1097 (47.3) | 514 (50.5) | 412 (54.4) |
| Wheezing in previous 12 months | 603 (26.0) | 227 (22.3) | 165 (21.8) |
| Cough without cold usually | 533 (23.0) | 247 (24.3) | 181 (23.9) |
| Cough 3 months each year | 544 (23.5) | 188 (18.5) | 141 (18.6) |
| Phlegm 3 months each year | 223 (9.6) | 125 (12.3) | 95 (12.5) |
| Breathing trouble ever | 587 (25.3) | 356 (35.0) | 261 (34.4) |
| Doctor-diagnosed chronic bronchitis | 198 (8.5) | 102 (10.0) | 75 (13.9) |
| Doctor-diagnosed emphysema | 34 (1.5) | 9 (0.9) | 6 (0.8) |
| Doctor-diagnosed asthma | 443 (19.1) | 243 (23.9) | 182 (24.0) |
| Current smoker | 279 (12.0) | 123 (12.1) | 96 (12.7) |
| Ex-smoker | 837 (36.1) | 427 (42.0) | 332 (43.8) |
| Response rate ≥45 yrs | 1613 (69.6) | 741 (72.9) | 557 (73.5) |
| Total n | 2319 | 1017 | 758 |
Data are presented as n (%), unless otherwise stated.