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Assessment of Child Anthropometry in a Large Epidemiologic Study
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Are small-for-gestational-age preterm infants at increased risk of overweight? Statistical pitfalls in overadjusting

Seham Elmrayed1, Amy Metcalfe2, Darren Brenner2

  • 1Department of Community Health Sciences, O'Brien Institute of Public Health, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada. Seham.elmrayed1@ucalgary.ca.

Journal of Perinatology : Official Journal of the California Perinatal Association
|April 14, 2021
PubMed

Insights

Adjusting for body measures like height and weight can falsely link small for gestational age (SGA) infants to later overweight status. These adjustments may create misleading associations, not reflecting a true direct effect.

Area of Science:

  • Pediatric Growth and Development
  • Nutritional Epidemiology
  • Biostatistics

Background:

  • Small for gestational age (SGA) is a predictor of adverse health outcomes.
  • The relationship between SGA and childhood overweight is complex and may be influenced by confounding factors.
  • Body measures at different time points can impact the observed association.

Purpose of the Study:

  • To investigate the impact of adjusting for body measures (height and weight) on the association between SGA and overweight at three years of age.
  • To determine if adjusting for intermediate body measures confounds the relationship between SGA and later overweight status.

Main Methods:

  • Analysis of data from the Preterm Infant Multicenter Growth Study (n=1089).
  • Logistic regression models were used to adjust for confounders, with separate adjustments for weight and height at 21 months.
  • Marginal structural models (MSMs) were employed to estimate the direct effect of SGA on overweight, controlling for body measures.

Main Results:

  • Crude and confounder-adjusted models showed no association between SGA and overweight.
  • Adjusting for height alone showed a positive association (OR: 2.31), while adjusting for weight showed a significant positive association (OR: 6.60).
  • MSMs, which held height and weight constant, found no direct effect of SGA on overweight (OR: 0.83 for height, OR: 0.71 for weight).

Conclusions:

  • Adjusting for body measures can alter the observed association between SGA and overweight.
  • Spurious associations between SGA and overweight can arise from adjusting for intermediate body measures.
  • The direct effect of SGA on overweight at 3 years is not supported when accounting for body measures using MSMs.
Abstract

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