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Smoking and the sudden infant death syndrome: results from 1993-5 case-control study for confidential inquiry into stillbirths and deaths in infancy

BMJ 1996; 313 doi: (Published 27 July 1996) Cite this as: BMJ 1996;313:195
  1. Peter S Blair, medical statisticiana,
  2. Peter J Fleming, professor of infant health and developmental physiologya,
  3. David Bensley, statisticianb,
  4. Iain Smith, senior lecturerc,
  5. Chris Bacon, consultant paediatriciand,
  6. Elizabeth Taylor, consultant senior lecturer in paediatricse,
  7. Jem Berry, professor of paediatric pathologyf,
  8. Jean Golding, professor of paediatric and perinatal epidemiologyg,
  9. John Tripp, consultant paediatricianh

    Confidential Enquiry into Stillbirths and Deaths Regional Coordinators and Researchers

  1. a Foundation for the Study of Infant Deaths Research Unit, Institute of Child Health, Royal Hospital for Sick Children, Bristol BS2 8BJ
  2. b Operational Research Division, NHS Executive, Quarry House, Leeds LS2 9UA
  3. c Nuffield Institute for Health, Leeds LS2 9PL
  4. d Friarage Hospital, Northallerton, North Yorkshire DL6 1JG
  5. e Sheffield Children's Hospital, Sheffield S10 2TH
  6. f University of Bristol, St Michael's Hospital, Bristol BS2 8EG
  7. g Institute of Child Health, Royal Hospital for Sick Children, Bristol BS2 8BJ
  8. h Department of Child Health, Postgraduate Medical School, Royal Devon and Exeter Hospital, Exeter EX2 5DW
  1. The regional coordinators and researchers of the confidential inquiry into stillbirths and deaths in infancy are given at the end of this article. Correspondence to: Professor Fleming.
  • Accepted 19 June 1996


Objective: To investigate the effects of exposure to tobacco smoke and of parental consumption of alcohol and illegal drugs as risk factors for the sudden infant death syndrome after a national risk reduction campaign which included advice on prenatal and postnatal avoidance of tobacco smoke.

Design: Two year population based case-control study. Parental interviews were conducted for each infant who died and four controls matched for age and date of interview.

Setting: Three regions in England with a total population of 17 million people.

Subjects: 195 babies who died and 780 matched controls.

Results: More index than control mothers (62.6% v 25.1%) smoked during pregnancy (multivariate odds ratio = 2.10; 95% confidence interval 1.24 to 3.54). Paternal smoking had an additional independent effect when other factors were controlled for (2.50; 1.48 to 4.22). The risk of death rose with increasing postnatal exposure to tobacco smoke, which had an additive effect among those also exposed to maternal smoking during pregnancy (2.93; 1.56 to 5.48). The population attributable risk was over 61%, which implies that the numbers of deaths from the syndrome could be reduced by almost two third if parents did not smoke. Alcohol use was higher among index than control mothers but was strongly correlated with smoking and on multivariate analysis was not found to have any additional independent effect. Illegal drug use was more common among the index parents, and paternal use of illegal drugs remained significant in the multivariate model (4.68; 1.56 to 14.05).

Conclusions: This study confirms the increased risk of the sudden infant death syndrome associated with maternal smoking during pregnancy and shows evidence that household exposure to tobacco smoke has an independent additive effect. Parental drug misuse has an additional small but significant effect.

Key messages

  • Exposure of babies to tobacco smoke from other members of the household before or after birth increases the risk of death: the greater the exposure the higher the risk

  • Over 60% of such deaths may be attributable to the effects of exposure to tobacco smoke before and after birth


  • Funding National Advisory Body for the confidential inquiry into stillbirths and deaths in infancy.

  • Conflict of interest None.

  • Accepted 19 June 1996
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