What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts

Brion, Marie-Jo A., Lawlor, Debbie A., Matijasevich, Alicia, Horta, Bernardo, Anselmi, Luciana, Araujo, Cora L., Menezes, Ana Maria B., Victora, Cesar G. and Smith, George Davey (2011) What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts. International Journal of Epidemiology, 40 3: 670-680. doi:10.1093/ije/dyr020


Author Brion, Marie-Jo A.
Lawlor, Debbie A.
Matijasevich, Alicia
Horta, Bernardo
Anselmi, Luciana
Araujo, Cora L.
Menezes, Ana Maria B.
Victora, Cesar G.
Smith, George Davey
Title What are the causal effects of breastfeeding on IQ, obesity and blood pressure? Evidence from comparing high-income with middle-income cohorts
Journal name International Journal of Epidemiology   Check publisher's open access policy
ISSN 0300-5771
1464-3685
Publication date 2011-01-01
Year available 2011
Sub-type Article (original research)
DOI 10.1093/ije/dyr020
Open Access Status Not yet assessed
Volume 40
Issue 3
Start page 670
End page 680
Total pages 11
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Subject 2713 Epidemiology
Formatted abstract
Background A novel approach is explored for improving causal inference in observational studies by comparing cohorts from high-income with low- or middle-income countries (LMIC), where confounding structures differ. This is applied to assessing causal effects of breastfeeding on child blood pressure (BP), body mass index (BMI) and intelligence quotient (IQ).

Methods Standardized approaches for assessing the confounding structure of breastfeeding by socio-economic position were applied to the British Avon Longitudinal Study of Parents and Children (ALSPAC) (N ≃ 5000) and Brazilian Pelotas 1993 cohorts (N ≃ 1000). This was used to improve causal inference regarding associations of breastfeeding with child BP, BMI and IQ. Analyses were extended to include results from a meta-analysis of five LMICs (N ≃ 10 000) and compared with a randomized trial of breastfeeding promotion.

Findings Although higher socio-economic position was strongly associated with breastfeeding in ALSPAC, there was little such patterning in Pelotas. In ALSPAC, breastfeeding was associated with lower BP, lower BMI and higher IQ, adjusted for confounders, but in the directions expected if due to socioeconomic patterning. In contrast, in Pelotas, breastfeeding was not strongly associated with BP or BMI but was associated with higher IQ. Differences in associations observed between ALSPAC and the LMIC meta-analysis were in line with those observed between ALSPAC and Pelotas, but with robust evidence of heterogeneity detected between ALSPAC and the LMIC meta-analysis associations. Trial data supported the conclusions inferred by the cross-cohort comparisons, which provided evidence for causal effects on IQ but not for BP or BMI.

Conclusion While reported associations of breastfeeding with child BP and BMI are likely to reflect residual confounding, breastfeeding may have causal effects on IQ. Comparing associations between populations with differing confounding structures can be used to improve causal inference in observational studies.
Keyword ALSPAC
Breastfeeding
Causation
Cognition
Cohort
Pelotas
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID 085515
G0600705
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Biological Sciences Publications
Institute for Molecular Bioscience - Publications
UQ Diamantina Institute Publications
 
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