Review of risk factors for Sudden Infant Death Syndrome

Abstract

Sudden infant death syndrome (SIDS) accounts for the largest number of deaths during the first year of life in developed countries. The possible causes of SIDS are numerous and, to date, there is no adequate unifying pathological explanation for SIDS. Epidemiological studies have played a key role in identifying risk factors, knowledge of which has underpinned successful preventive programmes. This review critically assesses information on the main risk factors and causal hypotheses put forward for SIDS, focusing on research published since 1994. The overall picture that emerges from this review is that affected infants are not completely normal in development, but possess some inherent weakness, which may only become obvious when the infant is subjected to stress. Initially there may be some minor impairment or delay in development of respiratory, cardiovascular or neuromuscular function. None of these is likely to be sufficient, in isolation, to cause death and, provided the infant survives the first year of life, may no longer be of any significance. However, when a compromised infant is confronted with one or more stressful situations, several of which are now clearly identified as risk factors, and from which the majority of infants would normally escape, the combination may prove fatal.

Prenatal Exposure to Carbon Monoxide Affects Postnatal Cellular Electrophysiological Maturation of the Rat Heart

“…1 Tobacco smoking is an important source of chronic exposure to carbon monoxide (CO): CO contained in cigarette smoke (Ϸ4%) easily crosses the placental barrier by passive diffusion, causing a 4-fold increase in carboxyhemoglobin levels in the umbilical cord blood. 2 The consequent chronic fetal hypoxia may retard fetal growth 2 and alter the physiological development of organs and tissues, especially those most susceptible to hypoxia damage, including the brain.…”

Changing Conclusions on Secondhand Smoke in a Sudden Infant Death Syndrome Review Funded by the Tobacco Industry

“…The contents of these 2 drafts were compared with each other and with the final published version, 16 and changes in the text were noted. Formal comments by PM executives made in response to the first draft and submitted to Frank Sullivan were also reviewed.…”

“…53 The SIDS review was published in April 2001. 16 The disclosure statement in the final publication stated, "We are grateful to Fabriques de Tabac Reunies SA (Philip Morris), Neuchatel, Switzerland, for financial support in the preparation of this review. The opinions expressed are entirely those of the authors."…”

“…36 They also agreed that "[a]ppropriate attribution for PM's support would be made," 36 which in the published article was described as only financial support. 16 In 1998, PM budgeted $50 000 to $100 000 for completion of Sullivan's review. 41,42 The Sullivan review article was part of PM's overall scientific strategic plan for addressing SHS and childhood health issues.…”

“…16 We identified and compared 2 drafts of the review in previously secret, internal tobacco industry documents that have been made available as a result of litigation against the industry, and we noted changes made after communications between the PM scientific executives and the authors. In response to the suggestions of PM, the authors removed SHS from their original conclusion that both prenatal exposure and postnatal exposure to tobacco smoke are independent risk factors for SIDS.…”