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What is SIDS?
Sudden Infant Death Syndrome (SIDS) is the “sudden death of an infant under one (1) 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” (Willinger, et al., 1991).
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SIDS is not... |
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- the major cause of death in infants from 1 month to 1 year of age, with most deaths occurring between 2 and 4 months
- sudden and silent - the infant was seemingly healthy
- a death often associated with sleep and with no signs of suffering
- a recognized medical disorder
- determined only after an autopsy, an examination of the death scene, and a review of the infant's and family's clinical histories
- a diagnosis of exclusion
- an infant death that leaves unanswered questions, causing intense grief for parents and families
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- preventable, but the risk can be reduced by placing a baby on his or her back to sleep on a firm surface, by making sure the baby has a smoke-free environment, and by keeping the baby from being overheated
- suffocation
- caused by vomiting and choking or by minor illnesses such as colds or infection
- caused by the diphtheria, pertussis, tetanus (DPT) vaccines or other immunizations
- contagious
- child abuse or neglect
- the cause of every unexpected infant death
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*Information provided by the National Sudden Infant Death Syndrome Resource Center 
Characteristics
What Are the Most Common Characteristics of SIDS?
Most researchers now believe that babies are born with one or more conditions that make them especially vulnerable to stressors that occur in the normal life of an infant, including internal and external influences. SIDS occurs in all types of families and is largely indifferent to race or socioeconomic level. SIDS is unexpected, usually occurring in otherwise apparently healthy infants from 1 month to 1 year of age. Most deaths from SIDS occur by the end of the 6th month, with the greatest number taking place between 2 and 4 months of age. A SIDS death occurs quickly and is almost always associated with sleep, with no signs of suffering. More deaths are reported in the fall and winter (in both Northern and Southern Hemispheres), and there is a 60-to-40 percent male to female ratio. African-American and American-Indian infants are two to three times more likely to die from SIDS as other infants. A death is diagnosed as SIDS only after all other probable alternatives have been eliminated. SIDS is a diagnosis of exclusion.
How Many Babies Die from SIDS?
SIDS claims the lives of almost 2,500 infants a year in the United States. Approximately 80 of those deaths occur in the State of Ohio each year. In spite of all the research to date, no one can yet tell us why.
SIDS remains the leading killer of infants one week to one year of age. More children will die of SIDS this year that will die of cystic fibrosis, childhood heart disease, childhood cancer and child abuse combined! Researchers believe that SIDS probably has more than one cause although the process of death may be similar in most instances. We do now know that the cause is not suffocation, aspiration, or regurgitation. SIDS has been an acceptable term for death certificates since 1973. You may know it’s more common name as “crib death”.
Medical Updates
Current Research Findings and Theories
Most scientists now believe babies who die of SIDS are born with one or more conditions that make them especially vulnerable to the internal and external stresses that occur in the life of any infant. Currently, many researchers argue that the clue to finding the cause(s) of SIDS lies in a further understanding of the development and functions of the brain and nervous system of SIDS infants.
These scientists theorize that some babies at risk for SIDS have defects in those parts of the nervous system that control breathing and heart rate. Maturation of the brainstem may be delayed in SIDS infants. Myelin, a fatty substance that facilitates nerve signal transmission, appears to develop more slowly in SIDS infants than in other babies.
"The detection of subtle abnormalities in SIDS brains indicates that not all SIDS infants are 'normal' despite their lack of clinical abnormalities. The occurrence of brain abnormalities supports the concept that a vulnerable, and not a normal, infant is at risk for SIDS. The idea of a vulnerable infant forms a key part of a triple risk model for the pathogenesis of SIDS." (Filiano and Kinney, 1994).
The Triple-Risk Model
Pathology studies of SIDS infants support the view that these infants possess underlying vulnerabilities that put them at risk for sudden death, a concept advanced by the triple-risk model in describing the sequence of events leading to the death of an infant. A number of scientists are currently applying this model in their search for a cause(s) of SIDS.
 Adapted from Filiano & Kinney 1994 |
Vulnerable Infant
The first key element of the triple-risk model depicts an infant with an underlying defect or abnormality, which makes the baby vulnerable. In this model, certain pathophysiological factors (e.g., defects in the parts of the brain that control respiration or heart rate, and that occur during early life) explain vulnerability to sudden infant death.
Critical Developmental Period
The second element of the triple-risk model refers to the infant's first 6 months of life. During this critical developmental period, rapid growth phases occur and changes in homeostatic controls take place. These changes may be evident (e.g., sleeping and waking patterns), or they may be more subtle (e.g., variations in breathing, heart rate, blood pressure, and body temperature). It may be that some of these changes may temporarily or periodically destabilize the infant's internal systems.
Outside Stressor(s)
The third element of this model involves outside stressors. These may include environmental factors (e.g., exposure to tobacco smoke, overheating, or prone sleep position) or an upper respiratory infection that most babies can experience and survive, but that an already-vulnerable infant may not be able to overcome. In and of themselves, these stressors do not cause infant deaths, but in a vulnerable infant, "may tip the balance against an infant's chances of survival" (Filiano and Kinney, 1994).
According to this model, all three elements must interact for a sudden infant death to occur - the baby's vulnerability is undetected until the infant enters the critical developmental period and is exposed to an outside stressor or stressors.
Brain Abnormalities in SIDS Infants
A team of researchers funded by the National Institute of Child Health and Human Development (NICHD) has discovered that infants who die of SIDS may have abnormalities in several parts of the brainstem. This finding builds on the results of an earlier study that identified abnormalities in the region of the brain known as the arcuate nucleus in babies who died of SIDS.
"These finding show that SIDS infants have a more global biological deficit than we previously believed - one that may originate in fetal life," explained Marian Willinger, Ph.D., of NICHD's Pregnancy and Perionatology Branch, in a May 2000 press release. In the NICHD study, SIDS infants were found to have decreased binding of serotonin in the nucleus raphe obscurus, a brain structure linked to the arcuate nucleus, as well as four other brain regions. These areas of the brain are thought to play a crucial role in regulating breathing, heart beat, body temperature, and arousal (Panigrahy et al., 200).
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