Intended for healthcare professionals

Rapid response to:


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

BMJ 2006; 332 doi: (Published 05 January 2006) Cite this as: BMJ 2006;332:18

Rapid Response:

The presumption of causality


The relative risk for associated factors should not be confused with
the attributable risk for causative factors. Li and colleagues [1]
evocatively express the risk associated with sudden infant death syndrome
(SIDS) & infant dummy use 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. 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 clearly 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. In SIDS research we
still need to determine what the protective mechanism might be, if indeed
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 appear to be as marked amongst 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 field [5].

1 Li D-K, Willinger M, Petitti DB, Odouli R, Liu L, Hoffman H. Use of
dummy (pacifier) during sleep and risk of sudden infant death syndrome.
BMJ (e-publication)

2 Mitchell EA, Taylor BJ, Ford RP, Stewart AW, Becroft DM, Thompson JM,
Scragg R, Hassall IB, Barry DM, Allen EM. Dummies and the sudden infant
death syndrome. Arch Dis Child 1993;68:501-4

3 Fleming PJ, Blair PS, Pollard K, Ward Platt M, Leach C, Smith I, Berry
PJ, Golding J. Pacifier use and sudden infant death syndrome: results from
the CESDI/SUDI case control study. Arch Dis Child 1999;81:112-116.

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;88:1058-1064

5 Mitchell EA, Blair PS, L’Hoir MP. Should pacifiers be recommended to
prevent SIDS? Pediatrics [In Press]

Competing interests:
None declared

Competing interests: No competing interests

20 December 2005
Peter S Blair
Research Fellow
Peter J Fleming
University of Bristol