Table 2

Estimated mean differences and 95% CIs in z-scores for growth parameters from multilevel modelling analyses in extremely preterm (EP) participants and term-born controls*

(A)
ParameterHeight z-scoreWeight z-scoreBMI z-scoreHead circumference z-score
Unadjusted model†
(n=489)
Unadjusted model†
(n=491)
Unadjusted model†
(n=486)
Unadjusted model†
(n=493)
Estimate (95% CI)Estimate (95% CI)Estimate (95% CI)Estimate (95% CI)
EP (Ref=controls)‡0.83 (−1.01 to −0.64)0.94 (−1.15 to −0.73)0.78 (−1.00 to −0.56)1.22 (−1.43 to −1.02)
Age at assessment§−0.00 (−0.01 to 0.00) 0.06 (0.05 to 0.07) 0.05 (0.02 to 0.07) 0.04 (0.03 to 0.05)
EP*age 0.04 (0.01 to 0.07)
(B)
Adjusted for sex¶
(n=489)
Adjusted for sex¶
(n=491)
Adjusted for sex¶
(n=486)
Adjusted for sex¶
(n=493)
Estimate (95% CI)Estimate (95% CI)Estimate (95% CI)Estimate (95% CI)
EP (Ref=controls)‡0.82 (−1.01 to −0.64)0.94 (−1.15 to −0.73)0.78 (−1.00 to −0.56)1.22 (−1.43 to −1.02)
Age at assessment§−0.00 (−0.01 to 0.00) 0.06 (0.05 to 0.07) 0.05 (0.02 to 0.07) 0.04 (0.03 to 0.05)
EP*age 0.04 (0.01 to 0.07)
Male (Ref=female)−0.05 (−0.23 to 0.13)0.02 (−0.18 to 0.23)0.06 (−0.14 to 0.26)−0.00 (−0.20 to 0.20)
  • *For all models, age was centred at 6 years to make intercept coefficients more meaningful.

  • †Variables in the model: group status (EP participants or controls), age at assessment and group*age interaction. Interactions were only shown if significant. Trajectories of height, weight and head circumference z-scores were similar in the EP and control groups. The group*age interaction was significant for BMI z-scores, indicating that the trajectory of BMI z-scores was different in the two groups.

  • ‡Estimates represent mean differences in growth measure z-scores between EP participants and controls.

  • §Estimates represent estimated average changes in growth measure z-scores over time: for instance, on average, weight increased by 0.06 SD per year and head circumference increased by 0.04 SD per year.

  • ¶Sex was further adjusted for to examine whether it would affect growth trajectories in the two groups. The group*sex interactions were insignificant (not shown), which indicates similar trajectories between females and males in both groups.

  • BMI, body mass index.