Characteristics of the subjects excluded and included in the analyses*
| Characteristics | Excluded (n=3050) | Included (n=4716) | P value† |
| Female sex, n (%) | 1546 (50.7) | 2327 (49.3) | 0.25 |
| Age, mean±SD (years) | 47.6±11.0 | 46.9±9.9 | 0.003 |
| Body mass index, mean±SD (kg/m2) | 25.6±4.4 | 25.3±4.0 | 0.006 |
| Low education, n (%) | 302 (9.9) | 269 (5.7) | <0.001 |
| Smoking habits, n (%) | <0.001 | ||
| Non-smoker | 1298 (42.7) | 2186 (46.6) | |
| Ex-smoker | 855 (28.1) | 1461 (31.1) | |
| Current smoker | 887 (29.2) | 1049 (22.3) | |
| Second-hand smoking, n (%) | 955 (31.4) | 1313 (27.9) | 0.001 |
| Past/current occupational exposure to vapours, gas, dusts or fumes, n (%) | 1343 (44.5) | 1947 (41.8) | 0.020 |
| Ever asthma, n (%) | 291 (9.6) | 368 (7.8) | 0.007 |
| High total serum IgE (>100 kU/L), n (%) | 577 (20.5) | 850 (18.9) | 0.107 |
| Allergen sensitisation‡, n (%) | 722 (24.8) | 1160 (25.2) | 0.70 |
| FEV1, mean±SD (L) | 3.41±0.83 | 3.51±0.79 | <0.001 |
| %FEV1/FVC, mean±SD | 79.3±6.0 | 79.0±5.8 | 0.043 |
| Slope, median (Q1–Q3) (% per µmol) | 1.0 (0.6–1.7) | 0.9 (0.5–1.6) | <0.001 |
*All characteristics were measured at the second examination except for the slope (assessed at the first examination); subjects were excluded from the analyses either if they did not participate in the third examination (n=2010) or if they had no prebronchodilator lung function data available (n=1040). Percentages were calculated on subjects with data available for each variable.
†Obtained using Pearson’s χ2 test (categorical variables), Kruskal-Wallis rank test (slope) or ANOVA (the remaining variables).
‡In the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults, specific IgE were only measured for subjects with a positive (>0.35 kU/L) Phadiatop Test (Phadia, Uppsala, Sweden); subjects with a negative test were assigned to the group with no sensitisation.