Baseline Characteristics
| . | Study Population . | Excluded From Analysis . | . | ||
|---|---|---|---|---|---|
| Categorical: n (%); Numeric: Mean (IQR) . | Missing Data . | Categorical: n (%); Numeric: Mean (IQR) . | Missing Data . | Excluded Compared With the Study Populationa . | |
| Children | |||||
| Boys (yes or no) | 164 (49) | 0 | 39 (51) | 0 | .81 |
| Pregnancy and birth | |||||
| Birth wt, kg | 3.51 (0.63) | 0 | 3.52 (0.57) | 0 | .87 |
| BMI at birth | 12.8 (1.75) | 0 | 12.8 (1.72) | 0 | .90 |
| Caesarean delivery (yes or no) | 78 (23) | 0 | 7 (9) | 0 | P = .005 |
| Early exposures | |||||
| Older children in household at 1 y (yes or no) | 138 (41) | 0 | 14 (27) | 26 | .06 |
| Duration of breastfeeding, mo | 0 | 16 | P = .005 | ||
| 0–3 | 31 (9) | 12 (20) | |||
| 3–6 | 76 (23) | 20 (33) | |||
| ˃6 | 227 (67) | 29 (48) | |||
| Maternal smoking during pregnancy (yes or no) | 43 (13) | 0 | 20 (26) | 0 | P = .004 |
| Nicotine level in hair at 1 y (ng/mg) | 3.3 (2.1) | 14 | 3.0 (4.4) | 29 | .73 |
| Nicotine level in hair at 3 y (ng/mg) | 2.0 (0.9) | 24 | 2.2 (0.6) | 65 | .91 |
| Day care | |||||
| Age at start, d | 372 (186) | 7 | 383 (189) | 26 | .74 |
| No. children in day care | 29 (41) | 12 | 16.9 (11) | 33 | P = .002 |
| Space per child, m2 | 13 (11) | 14 | 9.7 (6.9) | 34 | .08 |
| Indoor environment | |||||
| Cat at home at birth (yes or no) | 44 (13) | 3 | 16 (25) | 12 | P = .02 |
| Dog at home at birth (yes or no) | 49 (15) | 3 | 5 (8) | 12 | .13 |
| Socioeconomic variables | |||||
| Household annual income, 100 000 DKR | 5.09 (2.4) | 1 | 3.96 (2.0) | 25 | P < .001 |
| Mother’s education | 2 | 32 | .70 | ||
| College or lower level | 199 (60) | 26 (58) | |||
| Medium length | 89 (27) | 11 (25) | |||
| University | 44 (13) | 8 (18) | |||
| Mother’s employment | 112 (34) | 0 | 29 | .17 | |
| Nonprofessional | 112 (34) | 16 (33) | |||
| Professional | 156 (47) | 18 (38) | |||
| Student | 37 (12) | 5 (10) | |||
| Unemployed | 29 (9) | 9 (19) | |||
| Atopic disposition | |||||
| Father with asthma | 60 (18) | 9 | 8 (11) | 3 | .11 |
| . | Study Population . | Excluded From Analysis . | . | ||
|---|---|---|---|---|---|
| Categorical: n (%); Numeric: Mean (IQR) . | Missing Data . | Categorical: n (%); Numeric: Mean (IQR) . | Missing Data . | Excluded Compared With the Study Populationa . | |
| Children | |||||
| Boys (yes or no) | 164 (49) | 0 | 39 (51) | 0 | .81 |
| Pregnancy and birth | |||||
| Birth wt, kg | 3.51 (0.63) | 0 | 3.52 (0.57) | 0 | .87 |
| BMI at birth | 12.8 (1.75) | 0 | 12.8 (1.72) | 0 | .90 |
| Caesarean delivery (yes or no) | 78 (23) | 0 | 7 (9) | 0 | P = .005 |
| Early exposures | |||||
| Older children in household at 1 y (yes or no) | 138 (41) | 0 | 14 (27) | 26 | .06 |
| Duration of breastfeeding, mo | 0 | 16 | P = .005 | ||
| 0–3 | 31 (9) | 12 (20) | |||
| 3–6 | 76 (23) | 20 (33) | |||
| ˃6 | 227 (67) | 29 (48) | |||
| Maternal smoking during pregnancy (yes or no) | 43 (13) | 0 | 20 (26) | 0 | P = .004 |
| Nicotine level in hair at 1 y (ng/mg) | 3.3 (2.1) | 14 | 3.0 (4.4) | 29 | .73 |
| Nicotine level in hair at 3 y (ng/mg) | 2.0 (0.9) | 24 | 2.2 (0.6) | 65 | .91 |
| Day care | |||||
| Age at start, d | 372 (186) | 7 | 383 (189) | 26 | .74 |
| No. children in day care | 29 (41) | 12 | 16.9 (11) | 33 | P = .002 |
| Space per child, m2 | 13 (11) | 14 | 9.7 (6.9) | 34 | .08 |
| Indoor environment | |||||
| Cat at home at birth (yes or no) | 44 (13) | 3 | 16 (25) | 12 | P = .02 |
| Dog at home at birth (yes or no) | 49 (15) | 3 | 5 (8) | 12 | .13 |
| Socioeconomic variables | |||||
| Household annual income, 100 000 DKR | 5.09 (2.4) | 1 | 3.96 (2.0) | 25 | P < .001 |
| Mother’s education | 2 | 32 | .70 | ||
| College or lower level | 199 (60) | 26 (58) | |||
| Medium length | 89 (27) | 11 (25) | |||
| University | 44 (13) | 8 (18) | |||
| Mother’s employment | 112 (34) | 0 | 29 | .17 | |
| Nonprofessional | 112 (34) | 16 (33) | |||
| Professional | 156 (47) | 18 (38) | |||
| Student | 37 (12) | 5 (10) | |||
| Unemployed | 29 (9) | 9 (19) | |||
| Atopic disposition | |||||
| Father with asthma | 60 (18) | 9 | 8 (11) | 3 | .11 |
DKR, Danish kroner.
Calculated by χ2 test for categorical risk factors and student’s t test for numerical risk factors.