BMJ  2007;335:899 (3 November), doi:10.1136/bmj.39381.395197.BE

Letters

Allergy after breast feeding

Study was not designed to test the hypothesis

The first 150 words of the full text of this article appear below.

The PROBIT study is a large randomised controlled study aimed at reducing childhood gastrointestinal infection by promoting breast feeding. Secondary outcomes included atopic eczema and asthma.¹ However, the recent paper was written as if the study's main aim was to test the association between prolonged and exclusive breast feeding and asthma and allergy.² When no statistical difference was found, the authors erroneously concluded that breast feeding has no effect on these outcomes.

This conclusion cannot be drawn from this study design and cannot be extended to different populations. The post hoc analysis, with grouped breastfeeding classes, is more suited to the aim of the paper, but it has methodological and interpretative limitations, such as confounding.

The intervention promoted exclusive and prolonged breast feeding in women who wished to breast feed. This approach can test only whether the duration of breast feeding or exclusion of allergens in the first months of . . . [Full text of this article]

University of Otago, Christchurch; PO Box 4345; Christchurch; New Zealand

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• Kramer, M. S (2007). Testing hypotheses: reply. BMJ 335: 1061-1062 [Full text]  

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