Sudden infant death syndrome

doi:10.1016/S0140-6736(07)61662-6

The Lancet

Volume 370, Issue 9598, 3–9 November 2007, Pages 1578-1587

https://doi.org/10.1016/S0140-6736(07)61662-6 Get rights and content

Summary

Despite declines in prevalence during the past two decades, sudden infant death syndrome (SIDS) continues to be the leading cause of death for infants aged between 1 month and 1 year in developed countries. Behavioural risk factors identified in epidemiological studies include prone and side positions for infant sleep, smoke exposure, soft bedding and sleep surfaces, and overheating. Evidence also suggests that pacifier use at sleep time and room sharing without bed sharing are associated with decreased risk of SIDS. Although the cause of SIDS is unknown, immature cardiorespiratory autonomic control and failure of arousal responsiveness from sleep are important factors. Gene polymorphisms relating to serotonin transport and autonomic nervous system development might make affected infants more vulnerable to SIDS. Campaigns for risk reduction have helped to reduce SIDS incidence by 50–90%. However, to reduce the incidence even further, greater strides must be made in reducing prenatal smoke exposure and implementing other recommended infant care practices. Continued research is needed to identify the pathophysiological basis of SIDS.

Introduction

Sudden infant death syndrome, or 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”.¹ Despite declines in SIDS rates following risk reduction campaigns, SIDS continues to be the leading cause of death for infants aged between 1 month and 1 year in developed countries. Currently, Japan and the Netherlands have the lowest reported SIDS rates, at 0·09 and 0·1 per 1000 livebirths, respectively,2, 3 whereas New Zealand has the highest reported SIDS rate in developed countries, at 0·8 per 1000 livebirths.⁴ The USA and the UK have intermediate SIDS rates of 0·57 and 0·41 per 1000 livebirths, respectively.5, 6

In this Seminar, we focus on newer epidemiological and pathophysiological findings, risk reduction recommendations, and controversies related to some of these recommendations.

Section snippets

Epidemiology

In the 1980s and 1990s, after epidemiological studies showed a decreased incidence of SIDS in infants who slept supine, many countries implemented public-health campaigns to encourage families to place infants on their back for sleep. In most of these countries, the rate of placing infants prone for sleep has decreased 50–90%, and the rate of SIDS has similarly decreased 50–90%. As prone sleeping has become a less common risk factor, new epidemiological risk factors have emerged. We will

Diagnosis

By definition, SIDS is a diagnosis of exclusion. Protocols for standardised autopsies and death scene investigations in sudden unexpected infant deaths have been published.159, 160, 161 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. For example, autopsy rates in the Netherlands⁶¹ and Japan⁷⁰ are lower than in most other developed countries. Differences

Risk reduction interventions and their effect

Campaigns to reduce the risk of SIDS were initiated in the Netherlands in 1987; in the UK, New Zealand, and Australia in 1991, in the Scandinavian countries 1990–92, and in the USA in 1994.¹⁶⁸ These campaigns largely focused on reducing prone sleeping. Initially, recommendations stressed side or back placement, but after new research identified an increased risk with the side position compared with supine, subsequent recommendations include supine placement only.⁸⁴ Some campaigns have also

Management and support

The loss of an infant is devastating for everyone concerned. However, in addition to the loss of their infant, families whose infant has died of SIDS could face police investigation, a long wait for autopsy results, and continued uncertainty, leading to prolonged emotional distress, all of which complicate the grieving process. The physician can play an active part by advocating for an autopsy in all cases of sudden unexpected death, discussing the results of the autopsy with the family, and

Future directions

Despite declines in prevalence of SIDS, work still needs to be done on many fronts. Further refinement in elucidation of the risk and protective factors, with appropriately targeted and implemented interventions leading to increased adoption by families, could bring the number of SIDS deaths to lower and lower levels. However, the disorder is unlikely to be completely eliminated or reduced to the lowest possible rates until the specific causative mechanisms are understood more fully. Continued

Search strategy and selection criteria

We used the PubMed database to search for publications, using the search terms “SIDS,” “crib death,” “infant death,” and “sudden infant death syndrome.” Additionally, we reviewed listings of articles received through various mailing lists to identify publications that were not yet in PubMed. Citations were selected from articles published in English. We mostly selected publications from the past 5 years but did not exclude commonly referenced and highly regarded older publications.

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