Breast-feeding and health consequences in early childhood: Is there an impact of time-dependent confounding?

R. H H Groenwold*, K. Tilling, K. G M Moons, A. W. Hoes, C. K. Van Der Ent, M. S. Kramer, R. M. Martin, J. A C Sterne

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)

Abstract

Results: Weight and day care attendance appeared potential time-dependent confounders, since these predicted breast-feeding status and were influenced by previous breast-feeding. However, adjustment for time-dependent confounders did not markedly change the estimated associations. For example, in PROBIT the adjusted increase in BMI at 12 months per 1-month increase in exclusive breast-feeding was 0.04 (95% CI -0.09 to 0.01) using logistic regression and -0.06 (95% CI -0.11 to -0.01) using MSM. In Whistler, these estimates were each -0.05 (95% CI -0.10 to 0.00).

Conclusions: In two cohort studies, there was little evidence of time-dependent confounding by weight, length, rash, respiratory illness or day care attendance of the effects of breastfeeding on early childhood health.

Background: Estimated effects of breast-feeding on childhood health vary between studies, possibly due to confounding by baseline maternal and child characteristics. Possible time-dependent confounding has received little consideration. Our aim was to evaluate the impact of such confounding.

Methods: We estimated the relationship between cumulative exclusive breast-feeding up to 6 months and wheezing, rash and body mass index (BMI) at 12 months [in the Whistler cohort (n = 494) and PROBIT (n = 11,463)], and wheezing, rash, asthma, hay fever, eczema, allergy and BMI at age 6.5 years (PROBIT). We adjusted for time-dependent confounding by weight, length, rash, respiratory illness and day care attendance using marginal structural models (MSMs).

Original languageEnglish
Pages (from-to)139-148
Number of pages10
JournalAnnals of Nutrition and Metabolism
Volume65
DOIs
Publication statusPublished - 27 Nov 2014

Keywords

  • Bias
  • Breast-feeding
  • Marginal structural models
  • Time-dependent confounding

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