Table 1.
Population characteristics of symptom-free subjects at baseline
| Population characteristics, n=35 739 | |
| Age (years), mean (SD) | 43 (10) |
| Females (%) | 59.8 |
| Education | |
| Low, n (%) | 4365 (12.3) |
| Medium, n (%) | 18 467 (52.2) |
| High, n (%) | 12 016 (34.0) |
| Unclassifiable, n (%) | 504 (1.5) |
| Monthly income | |
| Low, n (%) | 4231 (12.0) |
| Medium, n (%) | 9416 (26.6) |
| High, n (%) | 17 189 (48.8) |
| Not reported, n (%) | 4364 (12.6) |
| Pack-years in ever smokers, median (IQR) | 8 (12) |
| Smoking | |
| Never smoker, n (%) | 16 979 (48.8) |
| Ex-smoker, n (%) | 11 259 (32.4) |
| Current smoker, n (%) | 6541 (18.8) |
| FEV1% predicted, mean (SD) | 96.0 (12.6) |
| FVC% predicted, mean (SD) | 100.1 (12.0) |
| FEV1/FVC% predicted, mean (SD) | 95.4 (7.8) |
| Biological dust | |
| No, n (%) | 23 252 (65.7) |
| Low, n (%) | 10 353 (29.3) |
| High, n (%) | 1774 (5.0) |
| Mineral dust | |
| No, n (%) | 28 094 (79.4) |
| Low, n (%) | 5279 (14.9) |
| High, n (%) | 2006 (5.7) |
| Gases/fumes | |
| No, n (%) | 19 228 (54.3) |
| Low, n (%) | 13 993 (39.6) |
| High, n (%) | 2158 (6.1) |
| Pesticides | |
| No, n (%) | 33 553 (94.8) |
| Low, n (%) | 1398 (4.0) |
| High, n (%) | 428 (1.2) |
| Solvents | |
| No, n (%) | 24 956 (70.5) |
| Low, n (%) | 8858 (25.0) |
| High, n (%) | 1565 (4.5) |
| Metals | |
| No, n (%) | 33 643 (95.1) |
| Low, n (%) | 1004 (2.8) |
| High, n (%) | 732 (2.1) |
Education: low education (no training, primary education, lower or prevocational education); medium education (general secondary education, secondary vocational or professional guiding, preuniversity education); high education (higher professional or university degree); unclassifiable (subjects with other than above-mentioned education).
Monthly income: low-income (monthly net income ≤ €1500); medium-income (monthly net income between €1500 up and €2500); high-income (monthly net income ≥ €2500); unknown (I do not know/I do not want to say).
Smoking: never smokers (never smoked or smoked for <1 year); ex-smokers (smoked for ≥1 year and stopped smoking for ≥1 month); current smokers (current smoker or stopped smoking <1 month).
FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity.