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

BMJ 2009; 339 doi: (Published 14 October 2009) Cite this as: BMJ 2009;339:b3666
  1. Peter S Blair, senior research fellow1,
  2. Peter Sidebotham, associate professor in child health2,
  3. Carol Evason-Coombe, research health visitor1,
  4. Margaret Edmonds, research health visitor1,
  5. Ellen M A Heckstall-Smith, research assistant1,
  6. Peter Fleming, professor of infant health and developmental physiology1
  1. 1Department of Community Based Medicine, University of Bristol
  2. 2Health Sciences Research Institute, University of Warwick
  1. Correspondence to: P Fleming, FSID Research Unit, St Michael’s Hospital, Bristol BS2 8EG peter.fleming{at}
  • Accepted 18 June 2009


Objectives To investigate the factors associated with sudden infant death syndrome (SIDS) from birth to age 2 years, whether recent advice has been followed, whether any new risk factors have emerged, and the specific circumstances in which SIDS occurs while cosleeping (infant sharing the same bed or sofa with an adult or child).

Design Four year population based case-control study. Parents were interviewed shortly after the death or after the reference sleep (within 24 hours) of the two control groups.

Setting South west region of England (population 4.9 million, 184 800 births).

Participants 80 SIDS infants and two control groups weighted for age and time of reference sleep: 87 randomly selected controls and 82 controls at high risk of SIDS (young, socially deprived, multiparous mothers who smoked).

Results The median age at death (66 days) was more than three weeks less than in a study in the same region a decade earlier. Of the SIDS infants, 54% died while cosleeping compared with 20% among both control groups. Much of this excess may be explained by a significant multivariable interaction between cosleeping and recent parental use of alcohol or drugs (31% v 3% random controls) and the increased proportion of SIDS infants who had coslept on a sofa (17% v 1%). One fifth of SIDS infants used a pillow for the last sleep (21% v 3%) and one quarter were swaddled (24% v 6%). More mothers of SIDS infants than random control infants smoked during pregnancy (60% v 14%), whereas one quarter of the SIDS infants were preterm (26% v 5%) or were in fair or poor health for the last sleep (28% v 6%). All of these differences were significant in the multivariable analysis regardless of which control group was used for comparison. The significance of covering the infant’s head, postnatal exposure to tobacco smoke, dummy use, and sleeping in the side position has diminished although a significant proportion of SIDS infants were still found prone (29% v 10%).

Conclusions Many of the SIDS infants had coslept in a hazardous environment. The major influences on risk, regardless of markers for socioeconomic deprivation, are amenable to change and specific advice needs to be given, particularly on use of alcohol or drugs before cosleeping and cosleeping on a sofa.


  • We thank the professionals from all the agencies in the south west of England who contributed to these studies, particularly the bereaved and control families.

  • Contributors: All authors contributed to the design of the study, revised the article, and approved the final version. PJF, PS, C E-C, and ME collected the data. PB carried out the initial analysis. PJF is guarantor.

  • Funding: This study was supported by research grants from the Foundation for the Study of Infant Deaths (FSID), Babes in Arms, and the charitable trusts of University Hospitals Bristol.

  • Competing interests: None declared.

  • Ethical approval: This study was approved by the south west multicentre research ethics committee and by each constituent local research ethics committee.

  • Accepted 18 June 2009

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