BMJ  2006;332:178 (21 January), doi:10.1136/bmj.332.7534.178-a

Letter

Dummies and SIDS

Causality has not been established

Editor—The relative risk for associated factors should not be confused with the attributable risk for causative factors. Li et al express the risk associated with sudden infant death syndrome (SIDS) and use of a dummy (pacifier) during sleep as a 90% reduction in risk, which could be potentially misunderstood and brings unwarranted media attention to what otherwise is a very interesting paper.¹

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Any calculation of attributable risk would be limited to the prevalence of exposure, which for dummy users in the Californian infant population would be 23% (based on the control data). However, projecting risk reduction or quantifying attributable risk in this study is inappropriate. As the authors point out in the discussion, a causal effect between dummy use and SIDS has not been established. The discrepancy in dummy use has already been reported in previous larger studies,^2-4 with better ascertainment levels providing a more cautious interpretation of the data.

Researchers in SIDS still need to determine what the protective mechanism might be, if it exists, or whether dummy use is a marker for something else. The discrepancy in dummy use between SIDS cases and age matched control infants for the last sleep does not seem to be as marked among routine users; this may indicate that infants are at greater risk of SIDS if they routinely use a dummy but have not been given their dummy on a particular night. Any discussion of potentially modifiable factors and impact on infant care practices is better served by a review on the subject taking into account a more detailed study of infant sleep behaviour and any detrimental effect of the exposure outside this research area.⁵

Institute of Child Life and Health, University of Bristol, Bristol BS2 8AE p.s.blair{at}bris.ac.uk

Institute of Child Life and Health, University of Bristol, Bristol BS2 8AE

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Competing interests: None declared.

References

1. Li D-K, Willinger M, Petitti DB, Odouli R, Liu L, Hoffman H. Use of a dummy (pacifier) during sleep and risk of sudden infant death syndrome. BMJ 2006;332: 18-21. (7 January.)[Abstract/Free Full Text]
2. Mitchell EA, Taylor BJ, Ford RP, Stewart AW, Becroft DM, Thompson JM, et al. Dummies and the sudden infant death syndrome. Arch Dis Child 1993;68: 501-4.[Abstract]
3. Fleming PJ, Blair PS, Pollard K, Ward Platt M, Leach C, Smith I, et al. Pacifier use and sudden infant death syndrome: results from the CESDI/SUDI case control study. Arch Dis Child 1999;81: 112-116.[Abstract/Free Full Text]
4. McGarvey C, McDonnell M, Chong A, O'Regan M, Matthews T. Factors relating to the infant's last sleep environment in sudden infant death syndrome in the Republic of Ireland. Arch Dis Child 2003;88: 1058-64.[Abstract/Free Full Text]
5. Mitchell EA, Blair PS, L'Hoir MP. Should pacifiers be recommended to prevent SIDS? Pediatrics (in press).

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Relevant Article

Use of a dummy (pacifier) during sleep and risk of sudden infant death syndrome (SIDS): population based case-control study

De-Kun Li, Marian Willinger, Diana B Petitti, Roxana Odouli, Liyan Liu, and Howard J Hoffman
BMJ 2006 332: 18-22. [Abstract] [Full Text] [PDF]

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