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Case-control study of sudden infant death syndrome in Scotland, 1992-5

BMJ 1997; 314 doi: (Published 24 May 1997) Cite this as: BMJ 1997;314:1516
  1. Hazel Brookea, executive director,
  2. Angus Gibson, chairmana,
  3. David Tappin, senior lecturer in community paediatrics, University of Glasgowa,
  4. Helen Brown, research associateb
  1. a Scottish Cot Death Trust, Royal Hospital for Sick Children, Glasgow G3 8SJ
  2. b Medical Statistics Unit, University of Edinburgh Medical School, Edinburgh EH8 9AG
  1. Correspondence and requests for reprints to: Mrs Brooke
  • Accepted 17 February 1997


Objective: To investigate the relation between routine infant care practices and the sudden infant death syndrome in Scotland.

Methods: National study of 201 infants dying of the sudden infant death syndrome (cases) and 276 controls by means of home interviews comparing methods of infant care and socioeconomic factors.

Results: Sleeping prone (odds ratio 6.96 (95% confidence interval 1.51 to 31.97)) and drug treatment in the previous week (odds ratio 2.33 (1.10 to 4.94)) were more common in the cases than controls on multivariate analysis. Smoking was confirmed as a significant risk factor (odds ratio for mother and father both smoking 5.19 (2.26 to 11.91)). The risk increased with the number of parents smoking (P<0.0001), with the number of cigarettes smoked by mother or father (P=0.0001), and with bed sharing (P<0.005). A new finding was an increased risk of dying of the syndrome for infants who slept at night on a mattress previously used by another infant or adult (odds ratio 2.51 (1.39 to 4.52)). However, this increased risk was not established for mattresses totally covered by polyvinyl chloride.

Conclusions: Sleeping prone and parental smoking are confirmed as modifiable risk factors for the sudden infant death syndrome. Sleeping on an old mattress may be important but needs confirmation before recommendations can be made.

Key messages

  • Parental smoking is currently the most important modifiable risk factor in the sudden infant death syndrome

  • In this study sleeping prone and, to a lesser extent, sleeping on the side increased the risk of the syndrome, so babies should be put down to sleep only on their back

  • Bed sharing with an infant should be discouraged if the mother smokes

  • Sleeping on an old mattress may carry an increased risk


  • Accepted 17 February 1997
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