Table 1.
Demographic characteristics of CLD patients in the first and second year of life (n = 1297)
| First year (n = 847) | Second year (n = 450) | χ 2 or U | p value* | |
|---|---|---|---|---|
| Male, n (%) | 483 (57.0) | 253 (56.2) | 0.08 | 0.781 |
| Caucasian, n (%) | 596 (70.4) | 306 (68.0) | 0.78 | 0.378 |
| Daycare attendance, n (%)a | 24 (2.8) | 52 (11.6) | 40.5 | <0.0005 |
| Siblings, n (%) | 519 (61.3) | 290 (64.4) | 1.26 | 0.262 |
| Mother smokes, n (%) | 116 (13.7) | 57 (12.7) | 0.27 | 0.604 |
| Mother smoked during pregnancy, n (%) | 108 (12.8) | 46 (10.2) | 1.84 | 0.176 |
| Smokers in the household, n (%) | 219 (25.9) | 112 (24.9) | 0.15 | 0.704 |
| ≥2 smokers in the household, n (%) | 76 (9.0) | 35 (7.8) | 0.54 | 0.464 |
| >5 people in the household, n (%) | 165 (19.5) | 100 (22.2) | 1.36 | 0.244 |
| Family history of atopy, n (%) | 379 (44.9) | 205 (45.7) | 0.07 | 0.796 |
| Multiple birth, n (%)a | 179 (21.1) | 121 (26.9) | 5.48 | 0.019 |
| Enrolment age, months (median [IQR]) | 6.4 (3.7–8.0) | 16.2 (14.0–19.3) | 381,150 | <0.0005 |
| Gestational age, weeks (median [IQR])a | 29.0 (26.1–37.0) | 27.0 (25.1–31.7) | 147,996 | <0.0005 |
| Birth weight, g (median [IQR])a | 1152 (790–2671) | 880 (698–1453) | 145,582 | <0.0005 |
| Enrolment weight, g (median [IQR]) | 5640 (4405–6950) | 8860 (7752–9960) | 341,962 | <0.0005 |
CLD chronic lung disease, IQR interquartile range
*p value <0.05 is significant
aVariables controlled for in Cox proportional hazard regression analyses