Sudden infant death syndrome: collaborative approach needed

SIDS is defined as “the sudden death of an infant under one year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.” SIDS is the leading cause of death for infants aged between one month and one year in developed countries. Lowest rates of SIDS in these countries are in Japan and The Netherlands (0.09 and 0.1 per 1000 live births, respectively). The UK rate is 0.41, the USA 0.57, and the highest rate for developed countries is in New Zealand, at 0.8 per 1000 livebirths.

Dr Rachel Moon, Children’s National medical Centre, Washington, DC, USA and colleagues say that campaigns to place children on their backs during sleep have massively reduced SIDS incidence, by between 50-90%. The age when infants are at highest risk is between two and four months, and 90% of SIDS deaths happen in the first six months of life. Boys are more likely than girls to die from SIDS, at a ratio of 60:40. Ethnic differences are also risk factors for SIDS. Infants in the USA who are African American, Native American or Alaska Native have SIDS rates two to three times the national average. Aboriginal Australian and Maori New Zealander infants are also at higher risk – with Maori infants six times more likely than the New Zealand population average to die from SIDS.

The authors discuss other SIDS risk factors, including maternal smoking during pregnancy. They say: “If in-utero smoke exposure was eliminated, a third of SIDS deaths could possibly be prevented.” As well as infants sleeping on their side or front, other SIDS risk factors include soft bedding and surfaces, warmer room temperatures, multiple layers of clothing or blankets, and bed sharing. The risk from bed sharing is particularly high when there are multiple bed sharers, when the infant is younger than 11 weeks, and when bed sharing occurs for the entire night. When the adult(s) sharing the bed is overtired or has consumed alcohol , this risk could increase further. However, there is growing evidence that room sharing without bed sharing – eg. having the infants crib in the same room – is associated with reduced risk of SIDS. Use of a pacifier (dummy) at sleep time has also been shown to reduce SIDS risk – even when the pacifier may become dislodged from the mouth shortly after sleep onset. This displacement could disrupt sleep and make the child more easily aroused from sleep, allowing increased responsiveness to a life-threatening challenge.

Infants in child-care settings make up 20% of SIDS deaths; the reasons for this are unclear. A large proportion of these deaths are in the first week of child care; thus stress and sleep disruption could be contributory factors.

Other risk factors discussed are low birth weight/premature birth, breastfeeding, and recurrence of SIDS in siblings. Siblings of SIDS victims are more likely to die from SIDS themselves than the general population. Although homicide should be considered as a possibility, a SIDS death in subsequent sibling is six times more likely to be SIDS than homicide. Pathophysiology of SIDS, autopsy and genetic factors are also discussed in the Seminar.

The authors say: “By definition, SIDS is a diagnosis of exclusion. Protocols for standardised autopsies and death scene investigations in sudden unexpected infant deaths have been published. However, there is wide variability in both the content and frequency with which these protocols are implemented across jurisdictions, both within countries and across different countries.”

They also say that the messages of established risk reduction interventions, such as infants sleeping on their backs and avoidance of smoke exposure in-utero, should be continually reinforced to new generations of health providers, parents, and carers. The American Academy of Pediatrics SIDS risk reduction recommendations, 2005 are also discussed.

The authors conclude that monitoring trends of SIDS is crucial. They say: “Continued research, surveillance, risk reduction campaigns, and standardisation of autopsy and scene investigation protocols and classification of deaths are all essential pieces to illuminating the SIDS puzzle and reaching our shared goal of eliminating it as a cause of infant death.”