Table 3

 Adjusted odds ratios for chronic lung disease (CLD) in the inception cohort (1998–1999) and the verification cohort (2000–2001)

Adjusted OR 1998–1999 cohort (95% CI)Adjusted OR 2000–2001 cohort (95% CI)
*Birth weight for gestational age groups 75th–89th, 90–96th and ⩾97th were combined because ORs were similar.
OR, Odds ratio; CI, confidence interval.
Size of cohort55995854
CLD (n (%))1235 (22%)1475 (25%)
Predictor variable
Gestational age
    31 weeks1.00 reference group1.00 reference group
    30 weeks2.05 (1.44 to 2.91)1.66 (1.21 to 2.26)
    29 weeks4.25 (3.07 to 5.88)3.26 (2.43 to 4.39)
    28 weeks7.59 (5.49 to 10.51)6.56 (4.95 to 8.70)
    27 weeks15.58 (11.26 to 21.57)13.55 (10.16 to 18.06)
    26 weeks25.37 (18.22 to 35.33)22.96 (16.95 to 31.11)
    25 weeks56.14 (38.86 to 81.10)52.22 (37.03 to 73.64)
    ⩽24 weeks85.70 (57.00 to 128.9)142.4 (93.14 to 217.7)
Weight for gestational age
    ⩾75th*0.54 (0.44 to 0.67)0.64 (0.53 to 0.71)
    25th–74th1.00 reference group1.00 reference group
    10th–24th2.05 (1.67 to 2.51)1.82 (1.49 to 2.23)
    3rd–9th4.01 (3.06 to 5.24)2.87 (2.21 to 3.75)
    <3rd6.25 (4.29 to 9.11)5.27 (3.43 to 8.09)
Male sex1.42 (1.22 to 1.65)1.63 (1.41 to 1.89)