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Rapid Responses: Rapid Responses published:
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USE of dummies and sudden infant death syndrome(SIDS)-cause and effect or mere association
- Hora Soltani (9 December 2005)
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Artificial
- Tracy Morter (9 December 2005)
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Risk of SIDS cannot be assessed in a case-control study design
- Christopher J Cates (9 December 2005)
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Dummies and unexpected death
- Tom Hughes-Davies (9 December 2005)
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Concerned re- this research
- Helen Young (10 December 2005)
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Dummy use and primary mode of death in SIDS
- J. Michael Simpson (14 December 2005)
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Comments onn SIDS and pacifiers Study
- Robin Burn (14 December 2005)
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Low response rates generate considerable uncertainty
- Christopher J Cates (14 December 2005)
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Last sleep in SIDS: a bad indicator?
- Roberto Buzzetti, Roberto D Amico (16 December 2005)
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The presumption of causality
- Peter S Blair, Peter J Fleming (20 December 2005)
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Other considerations with respect to pacifier use
- I. Campbell-Taylor (6 January 2006)
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Under-powered and over-interpreted
- Michael R Perkin (10 January 2006)
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Case-control study is appropriate but the intervention needs more justification.
- Dorairajan Kulandaivel (1 October 2006)
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Hora Soltani, Lead Research Midwife/honorary Research Fellow Derby City general Hospital
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Inaccurate reporting or exaggeration of research findings could cause a lot of confusion for practitioners and consequently for parents under their care. The conclusion made from this study is too strong, the authors have admitted limitations of this study and also acknowledged the fact that this simple association may not indicate a causal effect. Yet, in their (abstract) conclusion, they have stated that dummies reduce the risk of SIDS. The conclusion should be modified to reflect this lack of certainty and to reflect observed association rather than suggesting a cause and effect relationship. Competing interests: None declared |
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Tracy Morter, Mum CM3 5ZS
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What is with this current attitude to replacing the natural role of mum? Dummy use could be decreasing SIDS risk as it is mimicking what happens naturally, frequent nursing through the night and baby should be near to mum as nature intended. Parenting doesn't stop just because it's night time. All these gadgets, swings, seats, bottles, dummies..when all baby needs is a cuddle and breastmilk. We should copy fellow mammals, they seem to know better than we do. I'm also becoming increasingly suspicious as all the recent SIDS advice propelled and hyped up by the media at mothers is detrimental to breastfeeding. Competing interests: None declared |
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Christopher J Cates, General Practitioner Manor View Practice, Bushey Health Centre, London Road, Bushey WD23 2NN
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Sir, The reporting in the abstract of this study is frankly misleading. The case-control design is by definition unable to assess the risks of SIDS, as the researchers have started with infants who died of SIDS and compared use of a dummy in these patients and matched controls. They found that in infants who died of SIDS, the incidence of dummy use was lower than in the control group. There are many possible explanations for this association, and to jump from this finding to the conclusion that “use of a dummy seems to reduce the risk of SIDS” reads as if the study shows a causal association which cannot be justified by the data presented. The study shows an interesting association which merits further investigation, but the authors themselves caution in the discussion section of the paper that their results are “not proof of a causal effect.” There was a lower use of dummies in the SIDS group, but this does not necessarily mean that use of a dummy reduces the risk of SIDS, as this is only one of many possible explanations for the association found. Is it too much to ask that authors should report the results of their study without reversing the direction of the association, so that the limitations of the study design are reflected in the abstract, not just relegated to the discussion section? Competing interests: None declared |
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Tom Hughes-Davies, Retired paediatrician Breamore Marsh SP6 2EJ
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Active babies on their front drive forward relentlessly; turned turtle they move little. Asleep and guided by clothing a baby may twist his head at the end of the cot, damaging the neck or burying his face. Heat and illness make for restlessness; dummies pacify. Could this be a reason for the interesting association of De Kun Li and his colleasgues? Or are parents more readily roused by a cry from a normally quiet baby? Competing interests: None declared |
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Helen Young, Practice Development Midwife Weston Area Health Trust
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I am concerned how the general public might react to the publication of this piece of research. It may have found that pacifiers reduce the risk of cot death in this very small study. But the fact that it is a very small study should have been emphasised more. This may induce parents who are concerned about SIDS(Sudden Infant Death Syndrome) to buy and use a pacifier even if they had not thought about this already. This will impact on long term breastfeeding rates which has a much higher impact on long term health benefits of babies and their mothers. It may also induce families who smoke and who don't ensure their babies sleep on their backs that using a pacifier will somehow protect their child in adverse circumstances. I feel this research should have been published with some additional information on how the public should react. The BBC Breakfast show actually had a reporter supporting pacifier use as a result of this study. As we all know such a small study cannot be held as evidence to change practice so radically. I believe the BMJ has a responsibility to assist reporters in their understanding of research and it's use. Not once is it stated that a much larger prospective study would have to be done before a change of behaviour is advocated. Competing interests: None declared |
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J. Michael Simpson, Consultant anaesthetist Apartado 128 (PO box), 8401-902 Lagoa, Algarve, Portugal
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The paper's findings permit far-reaching and important considerations in SIDS. Its conclusions indicate the dummy not only structures a physical space external to the nose and mouth, but must also actively maintain airway patency, by splinting the mouth open and, as I have previously suggested in 2001, by depressing the obstructing tongue away from the palates. Together with the finding of considerable reduction in syndrome risk, such reasoning supports obstructive (or mixed) apnoea as being the predominant primary death mode in SIDS, rather than the only alternative, namely central apnoea, where subsequent hypoxia is not dependent on airway patency. Furthermore, the finding that dummy use has a protective effect against SIDS risk from a broad range of syndrome risk factors, including those associated with socioeconomic deprivation, supports the concept that their lethal mechanism ends in primary respiratory upper airway obstruction, rather than primary cardiac arrest. Competing interests: None declared |
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Robin Burn, Retired Burry Port SA16 0DX
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There is a body of evidence to suggest that Sudden Infant Death Syndrome commonly referred to as cot death is linked to a mild diffuse brain injury acquired by the foetus in utero or during the birth procedure linked to trauma. Untreated viral and bacterial infection during pregnancy, smoking and drinking alcohol, all increase the risk of early miscarriage and increases the risk of trauma during birth procedure. The ultimate pathology of brain injury is death of he foetus or newly born. Organisations linked to Sudden Infant Death Syndrome, agree on the links to Smoking and Alcohol intake during pregnancy, to increase risk of cot death. After reading the published article, I find no evidence of the research team making reference to these links and inferences. Should the following questions have been posed to the parents of the study and control groups? 1] Were you aware of an infection during pregnancy especially in the first trimester? 2] Did you risk miscarriage in the first trimester? 3] Did you experience birth intervention i.e. C-section or mechanical aid intervention? 4] Was the birth less than 2 hours or longer than 12 hours? 5] Was the birth preterm? 6] Were you aware of the newborn acquiring an infection during he first weeks? On the basis that the study group may have been affected by the above, then the control group should be free of the above influences. Other facts gleaned from the study should undergo further considerations. The discussion of sleeping position of, on back, versus prone, or on side, may not be a clear cut situation, as 51 studied children succumbed to cot death in spite of being placed to sleep on their backs. Should the researchers have considered the sleeping position in which they were found, or when they were laid down to sleep before death? Researchers in the US have reported increased maternal age, i.e. over 35 years of age, to increased risks of problematic pregnancies and births. In this study more than half of the study group were born to mothers of maternal age over 25 (it would be interesting to look at over 35 years of age, numbers) Finally the study group individuals had a birth weight of less than 2500 grammes five times greater than the control group. Competing interests: None declared |
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Christopher J Cates, GP Manor View Practice, Bushey Health Centre, London Road, Bushey WD23 2NN
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Editor – This study found that in infants who died from SIDS, the reported use of a dummy in the index sleep was 4.1%, in the 50% of eligible mothers who agreed to take part. The use of a dummy in the other 50% of eligible infants with SIDS is unknown. In the control infants the reported use of a dummy in the last sleep before interview was 23.6%, in the 40% of eligible mothers who agreed to take part. The use of a dummy in the other 60% of control infants is also unknown. This means that potentially the overall dummy use in all the cases was between 2% and 54% and in all the controls between 9% and 69%. None of the confidence intervals reported in the paper reflects uncertainty generated by those who declined to take part. Due to the low response rates, unadjusted odds ratios of anywhere between 0.01 and 7.7 are compatible with the study findings, when the total eligible population is considered. The authors conclude in their abstract that “use of dummy seems to reduce the risk of SIDS”, but it could just be that reported dummy use in infants who died from SIDS was low because more mothers who gave their infants dummies declined to take part in the study. The abstract also concludes that “use of a dummy possibly reduces the influence of known risk factors in the sleep environment” but this is based on a spurious use of confidence intervals for the subgroups involved (1). The more correct test of interaction reported in the results section showed that “the difference in odds ratios between infants who did or did not use a dummy was not significant.” There is much more uncertainty in this paper than the authors would have us believe from the abstract. The reporting contrasts sharply with the careful reporting of Fleming et al (2), and in my view Fleming’s more cautious conclusion still stands: “Further epidemiological evidence and physiological studies are needed before pacifier use can be recommended as a measure to reduce the use of SIDS”. 1. Altman DG, Bland JM. Statistics Notes: Interaction revisited: the difference between two estimates. BMJ 2003;326:219 2. Fleming PJ, Blair PS, Pollard K, Platt MW, 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(2):112-116. Competing interests: None declared |
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Roberto Buzzetti, epidemiologist 41100 MODENA (Italy), Roberto D Amico
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In our opinion methodological reasons should advise against giving any value to comparisons based on “last sleep” in studies about SIDS. The last sleep is an exclusive feature of a dead baby. Who doesn’t die cannot experience the “last sleep before dying”! It seems incorrect to surrogate the absence of last sleep in the control group with a “reference sleep” (that is only one particular sleep among many, and, therefore, should be considered "usual sleep"). It would be more reasonable to make comparisons based on common exposures (e.g. parent’s smoking, usual sleeping position, bed sharing, pacifier during usual sleep, etc). In a recently published meta-analysis, which focuses on the relationship between the use of a pacifier and SIDS(1), the effect of pacifier in the usual sleep, measured in terms of odds ratio, is smaller than that observed for the last sleep, thus suggesting caution when taking last sleep as an indicator. In the absence of clear and strong evidence in support of pacifiers (which could have some adverse effects on breast feeding), we think it would be more appropriate not to provide any recommendations. Best regards Roberto Buzzetti, MD
REFERENCES (1) Hauck FR, Omojokun OO, Siadaty MS. Do Pacifiers Reduce the Risk of Sudden Infant Death Syndrome? A Meta-analysis. PEDIATRICS Vol. 116 No. 5 November 2005, pp. e716-e723 (doi:10.1542/peds.2004-2631). Competing interests: None declared |
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Peter S Blair, Research Fellow University of Bristol, Peter J Fleming
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Sir, 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 a 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 |
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I. Campbell-Taylor, Clinical Neuroscientist Cape Breton IWA, Prince St,. Sydney, NS B1P 5N2
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While the authors have substantiated a compelling reason for positional issues in infants who use pacifiers during sleep, this important factor may well be influencing a basic risk for SIDS. All infants "spit up" (reflux). In adults, this occurs more often during sleep partly because of a reduction in swallowing , saliva swallowing being a major protection against reflux. Aspiration of refluxed material is, as we know, extremely dangerous and is not always identified at autopsy. Aspiration pneumonitis in the adult is often unidentified because of the lack of a witnessed event. The use of a pacifier stimulates saliva and, we may assume, also encourages swallowing. The supine position with the airway superior to the upper esophageal sphincter, thereby reducing the risk of aspiration of refluxed material, as well as increased (stimulated) saliva swallowing may both account for the protective effect. Competing interests: None declared |
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Michael R Perkin, Clinical Lecturer Paediatrics St George's, University of London
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I am absolutely staggered that your statistical reviewer allowed the authors to get away with the comment that the use of a dummy "possibly reduces the influence of known risk factors in the sleep environment". The three confidence intervals on which this statement is made are: 0.12-3.59, 0.1-13.4 and 0.02-3.27. These are all huge confidence intervals ranging from a 50 fold reduction to over a ten times increase. You cannot possibly draw any conclusions from these results whatsover and to have done so suggests a significant lapse in statistical reviewing standards. Competing interests: None declared |
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Dorairajan Kulandaivel, Dentist znd Public health professional. Inner South Community Health Service, Melbourne, 3181
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Editor, This is with respect to the study investigating the reduction in SIDS due to pacifier use. Pacifier use has been associated with vast advantages as well as disadvantages. It is comparable to that of a double edged sword. It is interesting that many mothers prefer to use pacifiers with their kids instead of breast feeding. Because studies have shown that it tends to reduce the duration of breast feeding in infants. For instance, a prospective cohort study showed that the use of pacifier reduced the duration of breast feeding.(1) But being a cohort study, there could be a potential possibility for “Hawthorne effect” where in the intervention or the attention of the researcher in itself has the potential to cause altered favorable or detrimental behavior. So it raises a question whether a case-control study performed by these authors is suitable for this situation than a cohort study. Although a cause and effect relationship is hard to bring about in a case-control study, the fact that it does account for only past feeding habits and has no effect on their feeding behavior is a matter of advantage. Although the research demonstrated a reduction in incidence of SIDS after pacifier use, it is mainly due to the ability of the pacifier to act as an impediment to the kid rolling over to a prone position when unobserved. And prone position has been shown to cause “less flexibility in heart rate variability, reduced arousal and waking ability and poor ventilatory and airway protective responses”.(2) Hence it would be practically prudent to introduce a public health intervention whose advantages clearly outweigh the disadvantages. If the chief means of occurrence of SIDS is argued to be due to hypoxia, than the immediate risk factor appears to be “prone position” of the kid, wherein the pacifiers help to prevent the kids from going to this vulnerable position. But other potential causes for SIDS in a kid such as anemia and placental abruptions(3) and even anaphylaxis has also been proposed. (4) Hence the introduction of pacifier is only helpful to remain the kid in supine position. If the case-control study has matched for the above confounding factors than effectiveness of the intervention could be justified. The impact of the use of pacifier on the health of the kid in general and the oral health specifically is still a matter of concern. Dental decay, occlusal changes, persistence of sucking habit into early adulthood and change in breathing patterns have also been recognized. Hence this article is ambiguous to a certain extent that it is providing biased information for the public. Although the use of pacifiers could potentially reduce the incidence of the kid going to the prone position, the disadvantages and the after effects of the use of pacifiers have to be considered for healthy public health intervention. Hence investigations and research into an intervention or device at positioning the kid in the supine position should be carried out rather than utilizing other easier but destructive forms of intervention. References: 1. Vogel A, Hutchinson B, Mitchell E. The impact of pacifier use on breastfeeding: A prospective cohort study. Journal of Paediatircs and Child health 2000; 37:58-63. 2. Galland B, Taylor B, Bolton D. Prone versus supine sleep position: A review of the physiological studies in SIDS research. Journal of Paediatircs and Child health 2002;38:332-338. 3. Klonoff-Cohen SH, Srinivasan PI, Edelstein LS. Prenatal and intrapartum events and sudden infant death syndrome. Paediatric and Perinatal Epidemiology. 2002;16:82-89. 4. Buckley MG, Variend S, Walls AF. Elevated serum concentrations of b-tryptase, but not atryptase, in Sudden Infant Death Syndrome (SIDS). An investigation of anaphylactic mechanisms. Clinical and Experimental Allergy. 2001;31:1696-1704. Competing interests: None declared |
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