Association of risk factors with wheeze in the second year of life: food allergy, feeding, smoke exposure, day care attendance, respiratory tract infections, eczema and study centre
|
Unexposed % (n/N) |
Exposed % (n/N) |
Wheeze in unexposed % (n/N) |
Wheeze in exposed % (n/N) |
Unadjusted IRR (95% CI) (P value) |
Primary model – Adjusted IRR (95% CI) (P value) (n=3612) |
Sensitivity model 1 – Adjusted IRR (95% CI) (P value) (n=4227) | |
| Food allergy | |||||||
| Food allergy diagnosed in first 2 years of life (yes vs no) | 98.6 (8654/8775) | 1.4 (121/8775) | 7.6 (655/8564) | 21.5 (26/121) | 2.84 (1.92 to 4.20) (<0.001) | 1.26 (0.55 to 2.91) (0.589) | |
| Feeding | |||||||
| Ever breast fed (yes vs no) | 8.8 (731/7607) | 91.2 (7607/8338) | 6.0 (44/731) | 7.9 (597/7607) | 1.30 (0.96 to 1.77) (0.089) | 0.67 (0.14 to 3.18) (0.615) | |
| Duration of breast feeding (per month increase) | 1.00 (0.98 to 1.02) (0.918) | 1.02 (0.92 to 1.12) (0.729) | |||||
| Age at introduction of solids (per month increase) | 0.98 (0.93 to 1.03) (0.384) | 0.94 (0.83 to 1.08) (0.410) | |||||
| Overlap of breast feeding/solids (per month increase) | 0.99 (0.96 to 1.03) (0.709) | 0.94 (0.82 to 1.07) (0.320) | 0.95 (0.90 to 1.00) (0.044) | ||||
| Smoke exposure | |||||||
| Mother ever smoked (yes vs no) | 59.8 (5243/8774) | 40.2 (3531/8774) | 7.0 (365/5243) | 9.0 (316/3531) | 1.29 (1.11 to 1.50) (0.001) | 1.06 (0.81 to 1.40) (0.673) | |
| Smoking at any time during pregnancy (yes vs no) | 91.8 (7843/8544) | 8.2 (701/8544) | 7.7 (601/7843) | 9.6 (67/701) | 1.25 (0.97 to 1.61) (0.086) | 0.66 (0.40 to 1.10) (0.112) | |
| Mother smoking at 1 year follow-up (yes vs no) | 84.6 (5894/6971) | 15.5 (1077/6971) | 6.9 (404/5894) | 7.9 (85/1077) | 1.15 (0.91 to 1.45) (0.237) | 1.62 (1.09 to 2.42) (0.017) | 1.45 (1.09 to 1.92) (0.011) |
| Other smokers in household (yes vs no) | 79.1 (6936/8774) | 21.0 (1838/8774) | 8.1 (561/6936) | 6.5 (120/1838) | 0.81 (0.66 to 0.98) (0.033) | 1.25 (0.85 to 1.85) (0.261) | |
| Day care attendance | |||||||
| Day care in first year of life (yes vs no) | 69.1 (4780/6922) | 30.9 (2142/6922) | 5.0 (239/4780) | 11.5 (247/2142) | 2.31 (1.93 to 2.76) (<0.001) | ||
| Day care in second year of life (yes vs no) | 44.7 (3908/8739) | 55.3 (4831/8739) | 4.0 (154/3891) | 10.8 (522/4820) | 2.74 (2.29 to 3.28) (<0.001) | ||
| Day care at any time in first 2 years of life (yes vs no) | 38.3 (3051/7966) | 61.7 (4915/7966) | 3.1 (93/3051) | 10.7 (526/4915) | 3.51 (2.82 to 4.38) (<0.001) | 1.63 (1.08 to 2.45) (0.020) | 1.70 (1.18 to 2.45) (0.004) |
| Respiratory tract infections | |||||||
| URTIs in first year of life (≥quarterly vs ≤one) | 45.2 (3142/6956) | 54.8 (3814/6956) | 3.3 (102/3142) | 10.2 (388/3814) | 3.13 (2.52 to 3.90) (<0.001) | 1.08 (0.75 to 1.56) (0.672) | |
| URTIs in second year of life (≥quarterly vs ≤one) | 42.1 (3626/8604) | 57.9 (4978/8604) | 3.8 (136/3626) | 10.8 (537/4978) | 2.88 (2.38 to 3.47) (<0.001) | 1.08 (0.72 to 1.62) (0.704) | |
| LRTIs in first year of life (≥quarterly vs ≤one) | 94.7 (6524/6886) | 5.3 (362/6886) | 6.2 (406/6524) | 22.4 (81/362) | 3.60 (2.83 to 4.56) (<0.001) | 1.87 (1.33 to 2.64) (<0.001) | 1.72 (1.25–2.36) (0.001) |
| LRTIs in second year of life (≥quarterly vs ≤one) | 91.0 7252/7967 | 9.0 715/7967 | 6.6 (479/7252) | 24.9 (178/715) | 3.77 (3.17 to 4.48) (<0.001) | 2.50 (1.83 to 3.41) (<0.001) | 2.36 (1.76–3.17) (<0.001) |
| Allergic disease | |||||||
| Eczema in first2 years of life (yes vs no) | 67.7 (4870/7198) | 32.3 (2328/7198) | 5.1 (247/4870) | 12.2 (284/2328) | 2.41 (2.03 to 2.85) (<0.001) | 1.20 (0.93 to 1.55) (0.158) | 1.35 (1.08–1.69) (0.009) |
| Study centre | |||||||
| Reykjavik | 87.8 (7700/8775) | 1075/8775 (12.3) | 6.4 (496/7700) | 17.2 (185/1075) | Baseline comparator | Baseline comparator | Baseline comparator |
| Southampton | 91.3 (8011/8775) | 8.7 (764/8775) | 7.3 (581/8011) | 13.1 (100/764) | 0.76 (0.60 to 0.97) (0.027) | 1.04 (0.65 to 1.68) (0.866) | 1.09 (0.74–1.60) (0.668) |
| Amsterdam | 92.9 (8153/8775) | 7.1 (622/8775) | 7.5 (614/8153) | 10.8 (67/622) | 0.63 (0.47 to 0.83) (<0.001) | 0.72 (0.36 to 1.41) (0.335) | 0.82 (0.54–1.24) (0.351) |
| Berlin | 85.3 (7482/8775) | 14.7 (1293/8775) | 7.1 (529/7482) | 11.8 (152/1293) | 0.68 (0.55 to 0.85) (<0.001) | 0.98 (0.69 to 1.39) (0.912) | 0.99 (0.73–1.35) (0.957) |
| Lodz | 85.7 (7520/8775) | 14.3 (1255/8775) | 8.8 (660/7520) | 1.7 (21/1255) | 0.10 (0.06 to 0.15) (<0.001) | 0.18 (0.08 to 0.42) (<0.001) | 0.17 (0.08–0.36) (<0.001) |
| Vilnius | 86.7 (7611/8775) | 13.3 (1164/8775) | 8.7 (659/7611) | 1.9 (22/1164) | 0.11 (0.07 to 0.17) (<0.001) | 0.34 (0.15 to 0.78) (0.010) | 0.33 (0.18–0.60) (<0.001) |
| Madrid | 89.6 (7865/8775) | 10.4 (910/8775) | 8.3 (654/7865) | 3.0 (27/910) | 0.17 (0.13 to 0.26) (<0.001) | 0.18 (0.08 to 0.39) (<0.001) | 0.23 (0.13–0.41) (<0.001) |
| Milan | 89.8 (7878/8775) | 10.2 (897/8775) | 7.6 (596/7878) | 9.5 (85/897) | 0.55 (0.43 to 0.71) (<0.001) | 1.33 (0.17 to 10.20) (0.781) | 2.67 (0.65–10.97) (0.172) |
| Athens | 90.9 (7980/8775) | 9.1 (795/8775) | 8.3 (659/7980) | 2.8 (22/795) | 0.16 (0.10 to 0.25) (<0.001) | 0.34 (0.05 to 2.61) (0.302) | 0.33 (0.04–2.40) (0.272) |
Primary model: includes all variables with P<0.1 in univariate analysis (gender, gestation, birth weight, birth length, ethnicity of father, maternal allergy, maternal asthma, paternal allergy, paternal asthma, mould in house, dog ownership, day care attendance, respiratory tract infections and eczema), plus food allergy, variables related to feeding and smoke exposure and study centre.
Sensitivity model 1: this was generated by applying backward deletion to the primary model. It includes overlap of breast feeding/solids, mother smoking at 1- year follow-up, gender, day care attendance, LRTIs, eczema and study centre.
IRR, incidence rate ratio; LRTIs, lower respiratory tract infections; URTIs, upper respiratory tract infections.