Although the rate of cot death in the UK has fallen dramatically since the early 1990s, specific advice to avoid dangerous co-sleeping arrangements is needed to help reduce these deaths even further, say the researchers.
The term sudden infant death syndrome (SIDS) was introduced in 1969 as a recognised category of natural death that carried no implication of blame for bereaved parents. Since then, a lot has been learnt about risk factors, and parents are now advised to reduce the risk of death by placing infants on their back to sleep, placing infants in the "feet to foot" position at the bottom of the cot, and keeping infants in a smoke-free environment.
But it is not clear which risk messages have been taken on board in different social or cultural groups, and little is known about the emergence of new or previously unrecognised risk factors.
So a team of researchers at the Universities of Bristol and Warwick studied all unexpected infant deaths from birth to two years in the southwest region of England from January 2003 to December 2006. This four-year study* was funded by The Foundation for the Study of Infant Deaths (FSID).
To investigate a possible link between SIDS and socioeconomic deprivation, they compared these deaths with a control group at ‘high risk’ for SIDS (young, socially deprived mothers who smoked) as well as a randomly selected control group.
Parents were interviewed shortly after the death and information was collected on alcohol and drug use. A detailed investigation of the scene and circumstances of death was also conducted by trained professionals.
Of the 80 SIDS deaths analysed, more than half (54 per cent) occurred whilst co-sleeping compared to 20 per cent co-sleeping rate amongst both control groups.
Much of this risk may be explained by the combination of parental alcohol or drug use prior to co-sleeping (31 per cent compared with 3 per cent random controls), and the high proportion of co-sleeping deaths on a sofa (17 per cent compared with 1 per cent random controls), say the authors.
A fifth of SIDS infants were found with a pillow for the last sleep and a quarter were swaddled, suggesting potentially new risk factors emerging.
The risk factors were similar whichever group the SIDS cases were compared with, suggesting that these risk factors for SIDS apply to all sections of the community and are not just a consequence of social deprivation.
Some of the risk reduction messages seem to be getting across and may have contributed to the continued fall in the SIDS rate, say the authors. However, the majority of the co-sleeping SIDS deaths occurred in a hazardous sleeping environment. The safest place for an infant to sleep is in a cot beside the parental bed in the first six months of life, they write.
Parents need to be advised to never put themselves in a situation where they might fall asleep with a young infant on a sofa. They also need to be reminded that they should never co-sleep with an infant in any environment if they have been drinking or taking drugs.
We have learnt that SIDS is largely preventable, says Edwin Mitchell, Professor of Child Health Research at the University of Auckland, in an accompanying editorial. It is important to monitor parents' knowledge and infant care practices to inform health education and promotion. Implementing what we already know has the potential to eliminate SIDS, the challenge now is how to change behaviour, he concludes.