Potential risk factors for wheeze by centre
| All centres (n=12 049) | Reykjavik (n=1341) | Southampton (n=1140) | Amsterdam (n=976) | Berlin (n=1570) | Lodz (n=1513) | Vilnius (n=1556) | Madrid (n=1387) | Milan (n=1486) | Athens (n=1080) | |
| Food allergy | ||||||||||
| Any food allergy diagnosed in first 2 years of life (%)* | 1.3 | 2.1 | 3.0 | 2.3 | 1.0 | 1.2 | 0.5 | 1.5 | 0.8 | 0.1 |
| IgE-mediated food allergy %* | 1.1 | 1.9 | 1.9 | 1.2 | 1.0 | 1.1 | 0.4 | 1.5 | 0.8 | 0.1 |
| Feeding | ||||||||||
| Ever breast fed (%)* | 90.8 | 98.4 | 89.8 | 81.3 | 95.8 | 90.5 | 94.9 | 86.1 | 91.0 | 83.1 |
| Duration of breast feeding (months), mean (SD)† | 6.1 (3.90) | 8.5 (3.46) | 5.4 (4.14) | 4.6 (3.41) | 6.4 (3.60) | 6.1 (4.44) | 5.7 (3.94) | 5.3 (2.98) | 7.1 (3.76) | 4.3 (3.28) |
| Age at introduction of solids (months), mean (SD)† | 5.3 (1.61) | 5.3 (1.20) | 5.1 (1.36) | 5.2 (1.47) | 5.5 (1.57) | 5.0 (1.27) | 5.7 (2.54) | 5.1 (1.39) | 5.6 (1.48) | 5.3 (1.44) |
| Overlap of breast feeding/solids (months), median (range)‡ | 0 (0–25.8) | 3.2 (0–18.4) | 0 (0–23.5) | 0 (0–15.4) | 1.1 (0–13.3) | 0 (0–15.3) | 0.1 (0–11.4) | 0 (0–11.3) | 2.1 (0–11.6) | 0 (0–25.8) |
| Smoke exposure | ||||||||||
| Mother ever smoked (%)* | 41.7 | 38.4 | 41.8 | 42.9 | 52.7 | 34.0 | 40.6 | 39.0 | 40.0 | 46.4 |
| Smoking at any time during pregnancy (%)* | 9.6 | 7.7 | 6.7 | 10.5 | 10.3 | 8.8 | 7.5 | 10.9 | 7.8 | 18.1 |
| Mother smoking at 1-year follow-up (%)* | 15.9 | 10.3 | 6.3 | 15.2 | 16.9 | 14.4 | 8.0 | 23.0 | § | 33.3 |
| Other smokers in household (%)* | 22.9 | 3.0 | 17.2 | 20.2 | 10.1 | 31.7 | 42.9 | 17.8 | 27.7 | 33.4 |
| Day care attendance | ||||||||||
| Day care in first year of life (%)* | 32.2 | 61.3 | 50.0 | 72.7 | 38.2 | 6.5 | 2.0 | 40.0 | § | 3.3 |
| Day care in second year of life (%)* | 55.3 | 93.7 | 58.6 | 83.4 | 81.2 | 18.6 | 27.2 | 63.6 | 62.5 | 17.6 |
| Day care at any time in first 2 years of life (%)* | 63.7 | 97.0 | 73.7 | 90.7 | 82.9 | 22.8 | 30.6 | 68.0 | § | 18.9 |
| Respiratory tract infections | ||||||||||
| Frequent URTIs (≥quarterly) in first year of life (%)* | 55.5 | 91.2 | 77.9 | 80.3 | 80.3 | 54.4 | 4.0 | 18.6 | § | 46.3 |
| Frequent URTIs (≥quarterly) in second year of life (%)* | 56.7 | 91.6 | 65.1 | 81.0 | 90.2 | 47.8 | 3.4 | 22.2 | 68.8 | 59.2 |
| Frequent LRTIs (≥quarterly) in first year of life (%)* | 5.4 | 20.9 | 5.5 | 1.3 | 4.6 | 3.4 | 0.3 | 6.0 | § | 0.8 |
| Frequent LRTIs (≥quarterly) in second year of life (%)* | 9.0 | 23.2 | 5.8 | 1.1 | 6.0 | 1.0 | 1.1 | 5.8 | 28.6 | 23.3 |
| Allergic disease | ||||||||||
| Eczema in first 2 years of life (%)* | 34.7 | 53.0 | 56.0 | 46.1 | 37.4 | 33.1 | 4.9 | 26.7 | § | 18.7 |
Study centre (n)=total number of infants recruited.
*P<0.05 using one-way analysis of variance to test differences between centres.
†P<0.05 using Kruskal-Wallis to test differences between centres.
‡P<0.05 using χ2 to test differences between centres.
§For Milan, no 1-year outcomes or variables dependent on these are specified because 1-year data were not available for most participants.
LRTIs, lower respiratory tract infections; URTIs, upper respiratory tract infections.