Lifelines study population characteristics
| Baseline assessment* (n=132 595) | Second assessment* (n=65 009) | |
| Sex | ||
| Male, n (%) | 55 315 (41.7) | 26 325 (40.5) |
| Female, n (%) | 77 280 (58.3) | 38 684 (59.5) |
| Age, mean±SD | 44.1±12.6 | 45.8±12.2 |
| Education† | ||
| Low, n (%) | 38 229 (28.8) | 18 796 (28.9) |
| Medium, n (%) | 53 433 (40.3) | 25 826 (39.7) |
| High, n (%) | 40 933 (30.9) | 20 387 (31.4) |
| Smoking status | ||
| Total never smoker, n (%) | 62 895 (47.4) | 31 542 (48.5) |
| Total former smoker, n (%) | 43 079 (32.5) | 23 149 (35.6) |
| Total current smoker, n (%) | 26 621 (20.1) | 10 318 (15.9) |
| Male never smoker, n (%) | 24 765 (44.8) | 12 175 (46.2) |
| Male former smoker, n (%) | 18 414 (33.3) | 9700 (36.8) |
| Male current smoker, n (%) | 12 136 (21.9) | 4450 (16.9) |
| Female never smoker, n (%) | 38 130 (49.3) | 19 367 (50.1) |
| Female former smoker, n (%) | 24 665 (31.9) | 13 449 (34.8) |
| Female current smoker, n (%) | 14 485 (18.7) | 5868 (15.2) |
| Pack-years smoking, mean±SD‡ | 11.8±10.9 | 11.2±10.4 |
| Asthma | ||
| Never diagnosed with asthma | 120 783 (91.2) | 60 468 (93.1) |
| Ever diagnosed with asthma | 11 612 (8.8) | 4453 (6.9) |
| Chronic bronchitis, n (%) | 8128 (6.1) | 2946 (4.5) |
| Usual sputum | 13 687 (10.3) | – |
| Chronic cough (daily cough, 3 months a year), n (%) | 9754 (7.4) | 3956 (6.1) |
| Usual cough | 19 564 (14.8) | – |
*For participants with complete data for chronic bronchitis, sex, age, educational attainment, BMI, smoking status, pack-years smoking, environmental tobacco smoke at home and nitrogen dioxide.
†Educational attainment levels: low=junior secondary/lower vocational or less; medium=senior secondary/secondary vocational; high=higher vocational/university.
‡Pack-years smoking are for current and former smokers (baseline: n=69 700; second assessment: n=33 467).
BMI, body mass index.