Published online March 1, 2006
PEDIATRICS Vol. 117 No. 3 March 2006, pp. 987-988 (doi:10.1542/10.1542/peds.2005-3023)

This Article Extract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Related articles in Pediatrics Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Owen, C. G. Articles by Smith, G. D. Search for Related Content PubMed Articles by Owen, C. G. Articles by Smith, G. D. Related Collections Nutrition & Metabolism Social Bookmarking                         What's this?

Differences Between Meta-analyses on Breastfeeding and Obesity Support Causality of the Association: In Reply

Christopher G. Owen, PhD
Peter H. Whincup, FFPH
Derek G. Cook, PhD
Division of Community Health Sciences
St George's, University of London
University of London
London SW17 0RE, United Kingdom

Richard M. Martin, MFPH
George Davey Smith, FRCP
Department of Social Medicine
University of Bristol
Bristol BS8 1TH, United Kingdom

In Reply.—

We are grateful to Harder et al for drawing attention to the discrepancy between the results of their systematic review¹ of the relations between breastfeeding and obesity prevalence, which reported a considerably stronger inverse association (pooled odds ratio [OR]: 0.75; 95% confidence interval [CI]: 0.69–0.82)¹ than we observed in our recent report (pooled OR: 0.87; 95% CI: 0.85–0.89).² They propose that the reason for the discrepancy is our inclusion of studies in which the formula-fed subjects included breastfed subjects, thereby reducing the strength of the association.

We do not believe that this is the correct explanation for the different findings of the 2 reviews. We have examined the effect of excluding 6 studies in which the formula-feeding group was not exclusive^3–8; this exclusion did not make any material difference to the results of our analysis (pooled OR: 0.88; 95% CI: 0.85–0.90). We believe that the crucial difference between the 2 reviews was that we included a report by Grummer-Strawn and Mei⁹ (based on a very large study of 177304 American children aged 4 years), which was not included in the Plagemann and Harder review.¹ As we stated in our article, exclusion of this very large study (which accounted for 73% of total weight in our analysis and showed an OR of 0.92 [95% CI: 0.90–0.95]) strengthened the relation between breastfeeding and obesity prevalence so that the effect estimate (OR: 0.73; 95% CI: 0.70–0.77) was in close agreement with that of Plagemann and Harder. Including the Grummer-Strawn and Mei study (which met the entry criteria of Plagemann and Harder, particularly the requirement for exclusivity of the formula-feeding group) strengthened the case for small-study bias in our study, leading us to use a fixed-effects analysis, which is less susceptible to this form of bias. Had the Grummer-Strawn and Mei report been included in the Plagemann and Harder review, we believe its findings would have become very similar to our own.

We agree with Harder et al that we need to address dose-response relationships as well as overall estimates in studying the relationship between breastfeeding and obesity prevalence. However, we believe that it is also very important to address the issue of confounding, particularly for social circumstances and maternal factors. Our more recent review of the relationship between breastfeeding and mean BMI showed that adjustment for confounding markedly attenuated both the strength of overall association and the evidence of a relationship between breastfeeding duration and BMI.¹⁰ The importance of confounding has also been highlighted by Nelson et al,¹¹ who showed that the association between infant feeding and overweight observed in a large cohort of 11998 American adolescents was lost in a sibling-pair analysis.

REFERENCES

1. Plagemann A, Harder T. Breast feeding and the risk of obesity and related metabolic diseases in the child. Metab Syndr. 2005;3 :222 –232[CrossRef]
2. Owen CG, Martin RM, Whincup PH, Davey Smith G, Cook DG. Effect of infant feeding on the risk of obesity across the life course: a quantitative review of the published evidence. Pediatrics. 2005;115 :1367 –1377[Abstract/Free Full Text]
3. Bergmann KE, Bergmann RL, Von Kries R, et al. Early determinants of childhood overweight and adiposity in a birth cohort study: role of breast-feeding. Int J Obes Relat Metab Disord. 2003;27 :162 –172[CrossRef][Web of Science][Medline]
4. Elliott KG, Kjolhede CL, Gournis E, Rasmussen KM. Duration of breastfeeding associated with obesity during adolescence. Obes Res. 1997;5 :538 –541[Web of Science][Medline]
5. Li L, Parsons TJ, Power C. Breast feeding and obesity in childhood: cross sectional study. BMJ. 2003;327 :904 –905[Free Full Text]
6. Strbak V, Skultetyova M, Hromadova M, Randuskova A, Macho L. Late effects of breast-feeding and early weaning: seven-year prospective study in children. Endocr Regul. 1991;25 :53 –57[Medline]
7. Toschke AM, Vignerova J, Lhotska L, Osancova K, Koletzko B, Von Kries R. Overweight and obesity in 6- to 14-year-old Czech children in 1991: protective effect of breast-feeding. J Pediatr. 2002;141 :764 –769[CrossRef][Web of Science][Medline]
8. Tulldahl J, Pettersson K, Andersson SW, Hulthen L. Mode of infant feeding and achieved growth in adolescence: early feeding patterns in relation to growth and body composition in adolescence. Obes Res. 1999;7 :431 –437[Web of Science][Medline]
9. Grummer-Strawn LM, Mei Z. Does breastfeeding protect against pediatric overweight? Analysis of longitudinal data from the Centers for Disease Control and Prevention Pediatric Nutrition Surveillance System. Pediatrics. 2004;113(2) . Available at: www.pediatrics.org/cgi/content/full/113/2/e81
10. Owen CG, Martin RM, Whincup PH, Davey Smith G, Gillman MW, Cook DG. The effect of breastfeeding on mean body mass index throughout life: a quantitative review of published and unpublished observational evidence. Am J Clin Nutr. 2005;82 :1298 –1307[Abstract/Free Full Text]
11. Nelson MC, Gordon-Larsen P, Adair LS. Are adolescents who were breast-fed less likely to be overweight? Analyses of sibling pairs to reduce confounding. Epidemiology. 2005;16 :247 –253[CrossRef][Web of Science][Medline]

---

PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics

CiteULike    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

Related articles in Pediatrics:

Differences Between Meta-analyses on Breastfeeding and Obesity Support Causality of the Association

Thomas Harder, Karen Schellong, and Andreas Plagemann
Pediatrics 2006 117: 987. [Extract] [Full Text]  

This Article Extract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Related articles in Pediatrics Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Owen, C. G. Articles by Smith, G. D. Search for Related Content PubMed Articles by Owen, C. G. Articles by Smith, G. D. Related Collections Nutrition & Metabolism Social Bookmarking                         What's this?