Table 3

Multilevel modelling: factors associated with growth trajectories within EP participants*

VariablesHeight z-score (unadjusted)Height z-score (adjusted†)
(n=277)
Estimate (95% CI)P valueEstimate (95% CI)P value
Gestational age (per week)0.05 (−0.11 to 0.21) (n=287)0.546
Moderate-severe brain injury (Ref=minor/none)−0.26 (−0.54 to 0.02) (n=286)0.068
Birth weight z-score (per SD)0.28 (0.13 to 0.43) (n=284)<0.0010.27 (0.13 to 0.41)<0.001
White ethnicity (Ref=other ethnicities)−0.65 (−0.94 to 0.37) (n=287)<0.001−0.65 (−0.92 to 0.38)<0.001
Ethnicity*age‡0.02 (0.00 to 0.05) (n=287)0.0410.03 (0.01 to 0.05)0.007
Enteral feeding begun before day 7 (Ref=no)0.33 (0.09 to 0.56) (n=279)0.0060.35 (0.13 to 0.57)0.002
Enteral feeding*age‡−0.02 (−0.04 to 0.00) (n=279)0.017−0.02 (−0.04 to 0.00)0.011
Steroids for chronic lung disease (per week)−0.03 (−0.07 to 0.01) (n=282)0.133
Weight z-score (unadjusted)Weight z-score (adjusted†)
(n=280)
Gestational age (per week)−0.01 (−0.20 to 0.18) (n=290)0.919
Moderate-severe brain injury (Ref=minor/none)−0.15 (−0.47 to 0.17) (n=289)0.363
Birth weight z-score (per SD)0.29 (0.12 to 0.17) (n=287)0.0010.28 (0.11 to 0.45)0.001
Birth weight z-score*age‡−0.03 (−0.04 to 0.01) (n=287)0.005−0.03 (−0.05 to 0.01)0.003
White ethnicity (Ref=other ethnicities)−0.63 (−0.95 to 0.30) (n=290)<0.001−0.63 (−0.95 to 0.32)<0.001
Ethnicity*age‡0.04 (0.00 to 0.07) (n=290)0.0300.04 (0.01 to 0.08)0.015
Enteral feeding begun before day 7 (Ref=no)0.42 (0.15 to 0.68) (n=282)0.0020.45 (0.19 to 0.70)0.001
Steroids for chronic lung disease (per week)−0.03 (−0.07 to 0.01) (n=285)0.141
BMI z-score (unadjusted)BMI z-score (adjusted†)
(n=276)
Gestational age (per week)−0.02 (−0.20 to 0.16) (n=286)0.813
Moderate-severe brain injury (Ref=minor/none)−0.01 (−0.32 to 0.31) (n=285)0.970
Birth weight z-score (per SD)0.13 (−0.04 to 0.30) (n=283)0.1440.13 (−0.04 to 0.31)0.133
Birth weight z-score*age‡−0.02 (−0.04 to 0.00) (n=283)0.017−0.03 (−0.05 to 0.01)0.014
White ethnicity (Ref=other ethnicities)−0.13 (−0.44 to 0.19) (n=286)0.432
Enteral feeding begun before day 7 (Ref=no)0.30 (0.03 to 0.56) (n=278)0.0260.29 (0.03 to 0.56)0.028
Steroids for chronic lung disease (per week)−0.01 (−0.05 to 0.03) (n=281)0.708
Head circumference z-score (unadjusted)Head circumference z-score (adjusted†)
(n=276)
Gestational age (per week)0.25 (0.05 to 0.44) (n=290)0.0130.46 (0.25 to 0.67)<0.001
Moderate-severe brain injury (Ref=minor/none)−0.19 (−0.53 to 0.16) (n=289)0.289
Birth weight z-score (per SD)0.31 (0.13 to 0.49) (n=287)0.0010.38 (0.19 to 0.56)<0.001
White ethnicity (Ref=other ethnicities)0.13 (−0.22 to 0.48) (n=290)0.467
Enteral feeding begun before day 7 (Ref=no)0.38 (0.09 to 0.66) (n=282)0.0090.30 (0.02 to 0.57)0.033
Steroids for chronic lung disease (per week)−0.05 (−0.10 to 0.01) (n=285)0.020−0.04 (−0.08 to 0.00)0.079
  • *For all models, age was centred at 6 years to make intercept coefficients more meaningful. One variable each time in the unadjusted models. For continuous variables (eg, birth weight z-score), estimate refers to estimated change in growth measure z-scores for per unit change in the predictor. For categorical variables, it refers to estimated difference in means relative to the reference group.

  • †Adjusted for age and variables with a p value <0.05 in the unadjusted models.

  • ‡Interactions with age at assessment were shown if significant. Significant interactions indicate that the impact of the predictor on the growth outcomes differed with age at assessment.

  • BMI, body mass index; EP, extremely preterm.