Last week I blogged about a new study purporting to show that there is a positive correlation between bed-sharing and SIDS. I promised to post more after I had a chance to read the article (Tappin et al., J Pediatrics 147, 32-37 (July 2005)).
Here's my executive summary of the article.
Over about four and a half years, the researchers obtained reports of all sudden unexplained infant deaths, implied to be throughout Scotland. They then attempted to interview the parents within 28 days. They eliminated from the group any infant for whom a cause of death could be identified and any infant whose parents they were unable to interview. That left 123 infants who died of SIDS in Scotland and whose parents were interviewed afterward.
The control group was obtained by selecting, for each infant in the SIDS group, the baby born immediately after and the baby born immediately before that baby in the same maternity ward. They attempted to interview each set of parents in the control group within 28 days of the associated "SIDS baby's" death. Those that were interviewed successfully numbered 263.
For the SIDS group "last sleep" in the questionnaire means the last sleep period before being found dead. For the control group "last sleep" means "last night."
The questionnaire asked about socioeconomic status, smoking, "In which room was your baby for most of the last sleep?", and "What was your baby's normal sleep place (day and night)?" If the baby shared a sleep surface during the last sleep, the parents were asked whether it was on a bed, couch, or chair; for how long; with whom; how close to others in the bed; and whether between people or between a person and an edge of the surface. They did not ask about alcohol because they did not have confidence that people would answer accurately.
Here are the reported data:
Normally slept in parental bed: 11% (13/123) of SIDS babies, 5% (13/263) of controls.
Shared surface during last sleep: 52% (64/123) of SIDS babies, 20% (53/263) of controls.
- Shared a couch: 11% (14/123) of SIDS babies, 1% (2/263) of controls.
- Shared a chair: 2% (2/123) of SIDS babies, no controls.
- Shared a bed: 37% (46/123) of SIDS babies, 19% (50/263) of controls.
(N.B. Of those 46 SIDS babies who shared a bed "during" their last sleep, 5 were recorded as found dead somewhere else: 2 in a crib/cot, 3 in a Moses basket. So:
- Were sharing a bed at time of death: 33% (41/123) of SIDS babies.)
- Sharing a crib with a twin: 2% (2/123) of SIDS babies, 1% (1/263) of controls.
In the same room as parents, not sharing a sleep surface: 36% (44/123) of SIDS babies, 63% (167/263) of controls.
In a separate room from parents, not sharing a sleep surface: 12% (15/123) of SIDS babies, 19% (43/263) of controls.
Another detail: Of the 46 SIDS babies who shared a bed during their last sleep, 30 were not breastfed or had been weaned from the breast by the time of the last sleep. This includes all the infants who actually died in the bed. All of the 16 breast-fed, co-sleeping SIDS babies were under 11 weeks of age. The number of control infants who were not breastfeeding is not reported explicitly in the article. Nor is the number of SIDS babies who didn't bed share and were not breastfeeding.
After doing the statistical analysis, the researchers arrived at the following results:
- Putting the baby to sleep in a separate room *is* measurably riskier than putting the baby to sleep in the same room *if* the parents are smokers. It is not measurably riskier if the parents are nonsmokers.
- Sharing a bed with parents at some time during the night, especially between the two parents, is measurably riskier than not sharing a bed when the child is younger than 11 weeks.
- The risk is still measurable even if the young (<11 weeks) infant is breastfed and even if the young infant's mother does not smoke.
- Sharing a bed with parents at some time during the night is NOT measurably riskier than not sharing a bed when the child is older than 11 weeks.
But because of the "wide confidence intervals," the researchers decline to conclude that it is safe for a child older than 11 weeks to co-sleep. I cannot evaluate the statistics well enough to comment on this, for example, the width of the confidence intervals here compared to the width of those supporting their other conclusions.
- Sharing a couch is measurably "associated with an increased risk."
- Socioeconomic status has no effect except insofar as it affects smoking, birth weight, maternal age, and sleep location.
- The strong effect of sleeping between two parents is possibly due to the known effect of sleeping in proximity to duvets and pillows. A previous study showed that 81% of infants bedsharing at death were covered by a duvet.
- Why was no connection found before? If there is no connection between bedsharing and SIDS for infants older than 11 weeks, then lumping all ages together as was done in some other studies might have obscured a connection between bedsharing and SIDS for infants younger than 11 weeks. Also, recently more people have been bedsharing, so the population available for study is greater and thus better able to demonstrate a connection.
The researchers recommend that all babies sleep in a crib in the parents' room.
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