A brief summary of new research findings and their potential significance based on presentations made at the SIDS International conference 2008 written by Professor Peter Fleming & Dr Pete Blair.

The epidemiology of sudden infant deaths is clearly changing, throughout the western world, with a gratifying continued fall in numbers of deaths, but a higher proportion (but not a higher number) of those deaths being of infants in bed with a parent. Several of the recent studies presented at this meeting showed the peak age of unexpected infant deaths has changed – having been around three to four months of age for the past 30 years, the peak age for such deaths is now around two months of age. This shift in age incidence seems to be a result of a bigger fall in the deaths of older infants than of younger infants rather than an increase in the number of younger infants who die in this way.

The continued importance of the known risk factors of front sleeping and exposure to tobacco smoke were confirmed in a number of studies, and the relative success of campaigns to reduce maternal smoking in pregnancy and the exposure of babies to tobacco smoke in infancy was also shown.

In some countries the fall in deaths certified as SIDS is partly related to diagnostic shift. Thus in some parts of the USA the term “positional asphyxia” rather than SIDS has been increasingly used to describe infants dying in the prone [front] sleeping position, or in bed with a parent. This seems to be misleading and inaccurate since there is almost always no direct evidence of an asphyxial process leading to the infant’s death.

The “triple risk” hypothesis of sudden infant deaths, which suggests that the deaths arise as a consequence of a particular stressor occurring to a vulnerable infant, at a particularly vulnerable stage of development was strongly supported by a range of new research, which emphasised that there may be a wide range of vulnerabilities and of final stressors that together may lead to death in different infants, with varying degrees of underlying vulnerability.

The potential importance of certain common bacteria - particularly E. coli and S. aureus- present in the airway and other sites, but not obviously causing infection was shown in a number of studies, though, despite several possible theories the mechanism by which such bacteria may contribute to the risk of unexpected infant death remains unclear.

The importance of a number of central neurotransmitters – the chemical messengers used in the brain to transmit information and to trigger responses – and their possible imbalance in some infants who die as SIDS – was the subject of several presentations. In particular, differences in the pathways that respond to the neurotransmitter serotonin have now been shown by several research groups to be a feature of some infants who die unexpectedly, though the mechanisms still remain unclear. Such abnormalities might reflect either an underlying vulnerability of some infants, or possibly be a consequence of the final sequence of events leading to the infants’ deaths. Many groups continue to work in this exciting area.

The question of why a larger number of infants than would be expected by chance continue to die unexpectedly whilst sharing a bed with a parent was the subject of several presentations and considerable discussion. It is now clear that parental smoking and use of alcohol or drugs are major contributory factors to many such deaths, as is the very dangerous practice of sleeping on a sofa or armchair with a baby. The question of whether bedsharing on a firm mattress (particularly by a breastfeeding mother) carries any increased risk of SIDS in the absence of smoking, alcohol or drugs remains unclear, but the evidence presented from the recent studies in England and in Ireland suggests that any such increase in risk is likely to be small, whilst the close two-way relationship demonstrated in the Avon Longitudinal Study of Parents and Children between bedsharing and successful breastfeeding for many mothers and infants emphasises the importance of further research in this area.

Finally, new data from the SWISS study in the Southwest of England showed for the first time evidence that the use of infant sleeping bags may help reduce the risk of SIDS. This study also showed a major reduction in the occurrence of head covering (a major risk factor for SIDS), possibly as a result of FSID’s “feet to foot” campaign.