Published 13 October 2009, doi:10.1136/bmj.b3466
Cite this as: BMJ 2009;339:b3466

Editorials

Risk factors for SIDS

We already know enough, the challenge is how to change behaviour

In the linked study (doi:10.1136/bmj.b3666), Blair and colleagues report on a four year case-control study of sudden infant death syndrome (SIDS) in south west England.1 The number of cases in the study is small, as a result of two factors. Firstly, the recommendation to avoid the prone sleeping position in the "Back to Sleep" campaign resulted in a dramatic reduction in mortality from SIDS in the early 1990s.2 Secondly, the change from the side to the back sleeping position led to the subsequent slower decline in mortality from SIDS.3 However, the study did come up with several important findings.

The study used two control groups—a random control group and a high risk group. The risk factors were similar whichever group the SIDS cases were compared with. This is important because it indicates that risk factors for SIDS apply to all sections of the community and are not just a consequence of social deprivation, because SIDS now occurs predominantly in disadvantaged communities. The prevalence of the exposure—for example, maternal smoking in pregnancy—may differ between advantaged and disadvantaged sections of the population. This is consistent with findings from New Zealand, where mortality from SIDS in Maori people is substantially higher than in non-Maori people, who are predominantly of European descent. This difference is accounted for by the higher exposure to maternal smoking and bed sharing in Maori people.4

Blair and colleagues’ study highlights co-sleeping as a risk factor for SIDS.5 6 7 8 More than half of deaths from SIDS occurred while the infant was sleeping with a parent. This is in accordance with other recent studies.7 8 Most authorities—for example, the American Academy of Pediatrics and the Ministry of Health in New Zealand—advise parents to avoid sharing a bed with their infant if they have been drinking or taking drugs.9 10 Presumably, alcohol and drugs impair the arousal of the adult co-sleeper. However, the dangers of this combination of behaviours are, for the first time, convincingly shown in this study. The box lists what we already know about SIDS and co-sleeping.


What is already known about SIDS and co-sleeping

  • Overwhelming evidence shows that bed sharing is a major risk for SIDS in infants of mothers who smoke.5 6 7 8 Maternal smoking has been shown to reduce an infant’s ability to arouse to various stimuli
  • In no group of infants or parents has bed sharing been associated with a reduced risk of SIDS
  • Recent studies have identified an interaction with age—infants under 12 weeks of age are at greater risk of SIDS with bed sharing than those over 12 weeks6
  • The risk of SIDS from bed sharing is slightly increased in infants under 12 weeks of age whose mothers do not smoke11
  • Infants who are returned to their own cot are not at increased risk of SIDS. This suggests that the problem relates to bed sharing per se rather than the type of person who bed shares with their infant
  • The longer the duration of bed sharing the higher the risk of SIDS5
  • Bed sharing with siblings poses a high risk


Co-sleeping on a sofa was an important risk factor for SIDS in Blair and colleagues’ study and previous studies from the United Kingdom. However, other studies from the United States,7 Germany,8 and New Zealand have not found such an association. Perhaps differences in the shape and softness of sofas in different countries account for this discrepancy.

The major disagreement in the bed sharing debate is whether the advice to avoid bed sharing should apply at all times in the first 6 months of life, or whether it is acceptable to condone or even encourage bed sharing in the small group that has not been shown to be at increased risk (infants of mothers who do not smoke, who are aged 3 months or more, and whose mothers have not taken alcohol or drugs and do not co-sleep on a sofa). Parents have the right to know this information, and all health professionals should advise parents that the safest place for an infant to sleep is in a cot beside the parents’ bed in the first 6 months of life.

So what needs to be done? We have learnt that SIDS is largely preventable. Further epidemiological studies will provide only relatively small gains and some clarification of the risk factors. It is important to monitor parents’ knowledge and infant care practices by periodic surveys so as to inform health education and promotion. These surveys are relatively cheap. Implementing what we already know has the potential to eliminate SIDS,12 so the major task is how to do it. Educational research is needed, in particular, how to change behaviour.

Cite this as: BMJ 2009;339:b3466

Edwin A Mitchell, professor of child health research

1 University of Auckland, Private Bag 92019, Auckland, New Zealand

e.mitchell{at}auckland.ac.nz

Research, doi:10.1136/bmj.b3666

Competing interests: None declared.

Provenance and peer review; Commissioned and not externally peer reviewed.

References

  1. Blair P, Sidebotham PD, Evason-Coombe C, Edmonds M, Heckstall-Smith EMA, Fleming P. Risky co-sleeping environments and risk factors amenable to change: case-control study of SIDS in south west England. BMJ 2009;339:b3666.[Abstract/Free Full Text]
  2. Dwyer T, Ponsonby AL, Blizzard L, Newman NM, Cochrane JA. The contribution in the prevalence of prone sleeping position to the decline in sudden infant death syndrome in Tasmania. JAMA 1995;273:783-9.[Abstract/Free Full Text]
  3. Mitchell EA, Hutchison L, Stewart AW. The continuing decline in SIDS mortality. Arch Dis Child 2007;92:225-6.
  4. Mitchell EA, Stewart AW, Scragg R, Ford RPK, Taylor BJ, Becroft DMO, et al. Ethnic differences in mortality rate from sudden infant death syndrome in New Zealand. BMJ 1993;306:13-6.[Abstract/Free Full Text]
  5. Scragg R, Mitchell EA, Taylor BJ, Stewart AW, Ford RPK, Thompson JMD, et al. Bed sharing, smoking and alcohol in the sudden infant death syndrome: results from the New Zealand cot death study. BMJ 1993:307:1312-8.
  6. Carpenter RG, Irgens LM, Blair PS, England PD, Fleming P, Huber J, et al. Sudden unexplained infant death in 20 regions in Europe: case control study. Lancet 2004;363:185-91.[CrossRef][Web of Science][Medline]
  7. Hauck FR, Herman SM, Donovan M, Iyasu S, Morre CM, Donoghue E, et al. Sleep environment and the risk of sudden infant death syndrome in an urban population: the Chicago infant mortality study. Pediatrics 2003;111:1207-14.[Abstract/Free Full Text]
  8. Vennemann M, Bajanowski T, Brinkmann B, Jorch G, Sauerland C, Mitchell E. Sleep environment risk factors for SIDS: the German SIDS study. Pediatrics 2009;123:1162-70.[Abstract/Free Full Text]
  9. American Academy of Pediatrics. The changing concept of sudden infant death syndrome: diagnostic coding shifts, controversies regarding the sleeping environment, and new variables to consider reducing the risk. Pediatrics 2005;116:1245-55.[Abstract/Free Full Text]
  10. Ministry of Health. Preventing sudden unexpected death in infancy: information for health professionals. 2008.www.moh.govt.nz/moh.nsf/0/5118C5C5561CEC79CC2573A6000B3BBE
  11. Carpenter RG. The hazards of bed sharing. Paediatr Child Health 2006;11(suppl A):24A-8A.
  12. Mitchell EA. SIDS: past, present and future. Acta Paediatr 2009 (in press).

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Hazardous cosleeping environments and risk factors amenable to change: case-control study of SIDS in south west England
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