Correspondence
The Risk of Sudden Infant Death
N Engl J Med 1994; 330:63-64January 6, 1994
- Article
To the Editor:
In their report on risk factors for the sudden infant death syndrome (SIDS) (Aug. 5 issue)1, Ponsonby et al. made one important omission. They failed to mention whether the criteria for SIDS were met. These include investigation at the scene, an autopsy, and a medical history of the infant2. The scene, at least in some cases, was investigated by ambulance attendants, and some portions of the medical history were elicited, but it was not mentioned whether an autopsy was performed. Without an autopsy a death cannot be ruled to be due to SIDS.
2 ReferencesStephen D. Cohle, M.D.
American Academy of Forensic Sciences, Colorado Springs, CO 80901-06691
Ponsonby A-L ,Dwyer T ,Gibbons LE ,Cochrane JA ,Wang Y-G . Factors potentiating the risk of sudden infant death syndrome associated with the prone position. N Engl J Med 1993;329:377-382
Full Text | Web of Science | Medline2
Valdes-Dapena M . A pathologist's perspective on the sudden infant death syndrome -- 1991. Pathol Annu 1992;27:133-164
Web of Science | Medline
To the Editor:
Among other factors, Ponsonby et al. found that the risk of SIDS increased nearly 20-fold if the infants slept prone on mattresses filled with either kapok or flakes of bark from the ti tree.
Using techniques we developed as part of ongoing studies of bedding factors in SIDS,1 we have tested the potential of several ti-tree mattresses from Australia to cause rebreathing of expired air. The results of our studies of ti-tree mattresses2 suggest that these mattresses are capable of causing lethal rebreathing if infants breathe continuously into them while lying face down. The degree of rebreathing is close to that with polystyrene-bead-filled cushions and sheepskins, which have been implicated in the deaths of other infants sleeping prone3-5. These three bedding materials are similar to one another in their degree of softness, malleability, and low resistance to airflow1. Obviously, our findings do not diminish the relative importance of other environmental or individual risk factors cited by Ponsonby et al.
5 ReferencesJames S. Kemp, M.D.
Bradley T. Thach, M.D.
Washington University School of Medicine, St. Louis, MO 631101
Kemp JS ,Nelson VE ,Thach BT . Measurement of bedding factors associated with presumed fatal rebreathing in prone-sleeping infants. Pediatr Res 1993;33:382A-382A abstract.
CrossRef2
Kemp J ,Thach B . New method for quantifying asphyxial rebreathing prior to death in “SIDS” infants. FASEB J 1992;6:A1231-A1231 abstract.
Web of Science3
Kemp J ,Thach B . Sudden death in infants sleeping on polystyrene-filled cushions. N Engl J Med 1991;324:1858-1864
Full Text | Web of Science | Medline4
Taylor BJ . A review of epidemiological studies of sudden infant death syndrome in southern New Zealand. J Paediatr Child Health 1991;27:344-348
CrossRef | Web of Science | Medline5
Kemp JS ,Thach BT . A sleep position-dependent mechanism for infant death on sheepskins. Am J Dis Child 1993;147:642-646
Web of Science | Medline
To the Editor:
Ponsonby et al. conclude that “when infants sleep prone, the elevated risk of SIDS is increased by each of four factors: the use of natural-fiber mattresses, swaddling, recent illness, and the use of heating in bedrooms.” However, I could not help noticing that each of those four factors actually reduced the risk of SIDS if infants did not sleep prone (their Table 1).
The authors did not explain the negative associations, nor did they explain why factors that seemingly reduced the risk of SIDS by themselves would exacerbate the risk of SIDS associated with the prone sleeping position. Although none of the negative associations were statistically significant, the consistency of the negative associations among all four factors deserves an explanation. It seems to indicate that there might be some underlying selection bias.
De-Kun Li, M.D., Ph.D.
Kaiser Permanente Medical Group, Oakland, CA 94611To the Editor:
Ponsonby et al. conclude from their study of sleeping position and SIDS that “healthy infants should not be placed prone to sleep.” Their data do not support this conclusion, particularly for infants in the United States.
The great majority of infants who slept prone, even on fiber mattresses, survived. For every 300 infants sleeping prone, only 2 died of SIDS. In a case-control study of more than 800 infants with SIDS, Hoffman and Hillman found only a marginal effect of sleeping position for U.S. infants.1 The many U.S. infants whose sleeping position may be changed from prone to lateral or supine may face considerable difficulty, or even risk. What will happen to babies who vomit while supine? What will happen to those with physically small airways or those with reduced upper-airway muscle tone? Are we sure that all such infants are now identified in early infancy? What will worried parents do to try to keep infants from rolling into the prone position?
Would it not be more prudent to advise parents to identify the position of greatest comfort for their infant?
1 ReferencesDaniel C. Shannon, M.D.
Massachusetts General Hospital, Boston MA, 021141
Hoffman HJ ,Hillman LS . Epidemiology of the sudden infant death syndrome: maternal, neonatal, and postneonatal risk factors. Clin Perinatol 1992;19:717-737
Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: In response to Dr. Cohle's question: all infants who died suddenly and unexpectedly in Tasmania during the study period were examined at autopsy by a hospital pathologist. The files for these deaths consisted of the autopsy report, a brief medical history of the infant, and the death-scene report.
The interesting findings of Drs. Kemp and Thach on the potential of different bedding materials to allow carbon dioxide rebreathing confirm the need for physiologic studies of the mechanism of the relation between prone position and SIDS. Bolton et al. also found that carbon dioxide rebreathing was increased for the face-down infant model in soft underbedding; an appropriate arousal response and the ability to move are important in these circumstances1. We await the results of further physiologic studies on the prone position and SIDS with interest.
We thank Dr. Li for the comments on Table 1. The evidence in our data that the four factors increase the risk of SIDS among infants sleeping prone is stronger than the evidence that they decrease risk among non-prone infants. Any inference that these factors have a protective role among infants in non-prone sleeping positions would have to be made cautiously. It is more likely that chance, selection bias, or confounding accounts for these negative associations than that they account for the positive associations. However, if future work did show these factors to be protective for non-prone infants but associated with increased risk for prone infants, then such results would be consistent with the action of the factors through an exaggeration of the original risk effect of a specified sleeping position on SIDS. For example, if swaddling stabilized an infant's sleeping position, then one would expect both the adverse effect of the prone position and the protective effect of the non-prone position to be enhanced.
We do not agree with Dr. Shannon's interpretation of the results of the National Institute of Child Health and Human Development case-control study. Infants with SIDS were more likely (P<0.05) to have slept prone than were controls2. Although the relative risk of SIDS for infants in the prone position was 1.4, the prevalence of the prone position was high (72 percent of control infants usually slept prone in the two weeks before the interview)2. A risk factor that is relatively weak (in terms of relative risk) and that is quite prevalent can account for more of the overall incidence of disease than a strong risk factor that is rarely present. The population-attributable risk3 for the prone position, based on this study, is 0.22 -- that is, 22 percent of deaths due to SIDS could theoretically be prevented in the United States by avoidance of the prone sleeping position for infants.
In 1992 the American Academy of Pediatrics recommended that “healthy infants, when being put down for sleep, be positioned on their sides or backs”4. This statement was made after a review of the effects of infants' sleeping positions on the incidence of SIDS and other outcomes, such as aspiration4. The recent decline in the rate of SIDS in King County, Washington, after an intervention to discourage the use of the prone sleeping position5 is consistent with the declines in the rate in several regions, including Tasmania, after similar interventions and provides further support for the recommendations of the American Academy of Pediatrics.
5 ReferencesAnne-Louise Ponsonby, B.Med.Sci., M.B., B.S.
Terence Dwyer, M.B., B.S., M.P.H., M.D.
Laura E. Gibbons, M.S.
Menzies Centre for Population Health Research, Hobart 7000, Tasmania, Australia1
Bolton DPG ,Taylor BJ ,Campbell AJ ,Galland BC ,Cresswell C . Rebreathing expired gases from bedding: a cause of cot death? Arch Dis Child 1993;69:187-190
CrossRef | Web of Science | Medline2
Hoffman HJ ,Hillman LS . Epidemiology of the sudden infant death syndrome: maternal, neonatal, and postneonatal risk factors. Clin Perinatol 1992;19:717-737
Web of Science | Medline3
Kahn HA, Sempos CT. Statistical methods in epidemiology. Vol. 12 of Monographs in epidemiology and biostatistics. New York: Oxford University Press, 1989.
4
AAP Task Force on Infant Positioning and SIDS
Web of Science | Medline5
Spiers PS, Guntheroth WG. Recommendations to avoid the prone sleeping position and recent statistics for SIDS in the United States. Am J Dis Child (in press).
- Citing Articles (1)
Citing Articles
1
William P. Fifer, Michael M. Myers. (2002) Sudden fetal and infant deaths: Shared characteristics and distinctive features. Seminars in Perinatology 26:1, 89-96
CrossRef
