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The British Medical Journal Releases Results of the National Scottish Case Control Study of SIDS

The Sudden Infant Death Syndrome Alliance

Media Alert

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TO: Affiliate Presidents and Executive Directors
FROM: Phipps Cohe, SIDS Alliance National Public Affairs Director
DATE: 5/22/97

RE: The British Medical Journal Releases Results of the National Scottish Case Control Study of SIDS
Embargoed until Friday, May 23, 1997

Sleeping on an old mattress, one previously used by another child or adult, may increase the risk for Sudden Infant Death Syndrome. This is just one of the findings released by the Scottish Cot Death Trust, appearing in the May 23, 1997 edition of the British Medical Journal--but it is surely the one which will receive the most media play.

The four year case control investigation of risk factors for Sudden Infant Death Syndrome in Scotland from 1992 to 1995 focused on routine child care practices and also examined practice on the night of death. It coincided with a period of decrease in the rate of SIDS deaths from 1.11 to 0.7 per 1000 live births. While the Scottish study confirms much of what we have come to accept with regard to SIDS risk factors, it also takes a thought-provoking look at some emergent post Back To Sleep risks.


An unexpected result from the Scottish study was the finding of an increased risk of SIDS for infants sleeping on mattresses previously used by other children or adults. This risk was associated with cloth-covered mattresses and mattresses topped with ventilated foam covered by netting. There was, however, no detectable risk with old mattresses covered by polyvinyl chloride (PVC). This may be explained by the fact that urine, sweat, and household fungi are not absorbed by the vinyl covering, which can be kept clean regardless of age.

The study in no way implies that previously used mattresses cause infant deaths. The study also suggests that mattresses with PVC coatings are associated with a lower risk of SIDS compared with other mattress types, disproving an earlier British television claim. There was not enough data available to explore an interaction between old mattresses and routine bedsharing.


Although stomach-sleeping continued to present a strong risk factor, its low prevalence in the infant population in Scotland indicates that only a small percentage of SIDS deaths can now be attributed to this. Sleeping on the back was found to be the safest, with more deaths associated with side sleeping. Regardless of the position in which babies were placed for sleep or found, SIDS babies were less likely to change position as regularly during sleep; they had fewer spontaneous arousals and fewer movements during sleep.


Pillows and duvets were more commonly used on the night of death than routinely. SIDS infants had a high thermal score of bedding plus clothing.

Prior to their deaths, SIDS babies were usually found to be sweaty on awakening.


The Scottish study found a greatly increased incidence of bed-sharing among SIDS cases at the time of death; 8% of the study participants reported routine bedsharing compared with 34% reporting bedsharing at the time of the baby's death. Bedsharing when the mother was smoking carried an increased risk.


Parental smoking during and after pregnancy was confirmed to be a major, potentially modifiable risk factor for SIDS. Risk was found to increase with the number of cigarettes smoked by the mother, father, and other people in the household. The risk also increased significantly with exposure. The finding of a dose response with the number of people smoking in the household adds weight to the possibility of smoking being causally related to SIDS, as does the increased risk related to the number of cigarettes smoked. The authors speculate that if smoking is causal, as many as two-thirds of SIDS cases might be avoided if mothers did not smoke during and after pregnancy.


SIDS victims were more likely to have had one or more of a range of symptoms--including, but not limited to, unusual sleepiness, sniffles and sickness--and to have been seen by their physician because of illness during the previous week. Receiving medications in the week before death has emerged as a risk factor in the multivariate analysis, however, no particular medication was found to be significant.


More babies died of SIDS on weekends than would be expected by chance, with 11% of the deaths occurring when the infants were away from home. Also of interest was a shift in the average age of the mothers of the SIDS victims studied. Mothers were older overall than in a previous national study (72% were aged 25 or more during 1992-95 compared with 30% during a national study conducted in 1981-82). The authors hypothesize that this swing may account for about 9% of the decrease in the rate of SIDS between the two studies.

For more information--or to request a copy of this 10-page study--contact the SIDS Alliance national office at 1-(800)221-SIDS.

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