Sudden Infant Death Syndrome

Leanne Paris

Augustana University College


A paper submitted to Dr. Jayne Gackenbach as part of the course requirements for Psy 473 (Sleep and Dreams), April, 1997


Sudden Infant Death Syndrome (SIDS) is one of the predominate unsolved problems of early infancy. The number of children who die of SIDS each year is higher than the number of those who die of cancer, heart disease, pneumonia, child abuse, AIDS, cystic fibrosis and muscular dystrophy combined. There is agreement in designating the diagnostic term, Sudden Infant Death Syndrome and defining it as an assumed clinical entity: the sudden and unexpected death of an apparently well, or almost well, infant, whose death remains unexplained after the performance of an adequate autopsy (Valdes-Dapena, 1979). This essay will outline the various aspects of Sudden Infant Death Syndrome and will help in broadening public knowledge of the tragic event.

Each year, thousands of children are found dead in their cribs for unexplained reasons. In urban regions of the United States of America, the incidence of SIDS may be as high as two to three deaths for each 1 000 live births (Marlow, 1973). SIDS accounts for 1 000 deaths each year in Canada, more than 7 000 deaths each year in the United States of America and 1 500 deaths a year in Britain (Caldwell, 1995). Within Canada, the rate in the Northwest Territories is five times higher than the rate in Quebec (Caldwell, 1995). The reason for the difference in the number of occurrence is not known. In developed countries where medical facilities are reliable and there is a fairly low proportion of socioeconomically deprived people, SIDS is without a doubt one of the leading causes of death in the postneonatal stage of life. There is no evidence that the mortality rate in SIDS is increasing, rather it seems to be decreasing. Children who die as a result of SIDS are usually between two and four months of age and appear to be well developed and nourished. It is quite uncommon for these unexpected deaths to occur at ages earlier or later than this.

There is a lack of agreement that such deaths are caused by a single mechanism. And there are a number of demographic factors which can attribute to a greater chance of an infant being at risk of Sudden Infant Death Syndrome. The less a child weighs at birth, the greater the possibility of crib death occurring is. SIDS is more common in males than it is in females. Moreover, it is more likely to happen between midnight and nine in the morning, than the rest of the day. Some observers have recorded an increased occurrence of SIDS on weekends than weekdays. In the United States, the incidence of SIDS is higher among American Indians, African Americans and Mexican Americans than it is among Caucasians. And there are more cases of SIDS in children of socioeconomically deprived families residing in areas where housing and sanitation are poor than from more privileged ones.

Furthermore, the rate of Sudden Infant Death Syndrome is higher among children born out of wedlock. Infants whose mothers smoked during their pregnancy are more likely to become victims of SIDS. Also, it is more prevalent in families where cigarette smoke is found in the home regularly (Caldwell, 1995). SIDS deaths do recur in families, the rate among siblings of babies who die of SIDS is four to seven times higher than that for the general population (Valdes-Dapena, 1979). In subtropical and temperate climates, there is a very small difference in the rate of unexplained deaths occurring between the summer and winter months. However, in parts of the world where there is great seasonal temperature changes, far more incidences take place during the winter than the summer. This finding has created a hint that cold weather may be in some way linked to the pathogenesis of SIDS (Valdes-Dapena, 1979).

While they are sleeping, infants normally experience apnea (temporary stopping of breathing). If the pause is too long, a healthy baby will wake up to breathe, but if the baby is not able to wake himself or herself up for some reason, accidental suffocation and sudden death can occur (Wellness Web, 1997). When babies are allowed to sleep in a prone or face-down position and when they are heavily wrapped, they are put at higher risk of this happening and therefore, Sudden Infant Death Syndrome takes place much more frequently. The risk for SIDS increases dramatically with the combination of viral illness, heavy wrapping and being placed to sleep in the prone position (Caldwell, 1995).

Sudden Infant Death Syndrome is a mysterious event because little is known about the clinical manner of the death. Most babies who die of SIDS, die at home, during the night and unobserved. At the time of death, the child is rarely being watched. The episode has been described by people who have witnesses it; an otherwise apparently healthy baby suddenly turns blue, stops breathing and becomes limp. There is no cry or no struggle (Valdes-Dapena, 1979). There is no forewarning evidence for some children who die of SIDS, but many do have trivial symptoms, particularly that of a mild upper respiratory infection. "Near misses," in which the baby has an extended apneic incident and appears to be dead, but is resuscitated by a timely interference are rare. Apparently, some of these infants continue to lead normal lives, whereas others are victims of a similar experience within a comparatively short period of time (Valdes-Dapena, 1979).

Numerous new studies have been initiated to learn about the reasons how and why Sudden Infant Death Syndrome happens. Scientists are examining the development and function of the nervous system, the brain, the heart, breathing and sleep patterns, body chemical balances, autopsy findings and environmental factors. There is a possibility that SIDS, like many other medical disorders, will one day have more than one explanation (The SIDS Network, 1997).

Furthermore, there is presently extensive research being carried out in an effort to determine the pathogenic elements responsible for such deaths because the mechanism of Sudden Infant Death Syndrome is unknown. The baby is usually described as being normal, well-developed and well-nourished. Data gathered recently indicates that many of the children who have died without sufficient explanation had difficulties in the neonatal stage, as well as in many situations, the postneonatal stage was characterized by poor growth and lack of vigor (Valdes-Dapena, 1979). After an autopsy is performed on a baby who has died of SIDS, only minor pathologic changes are found. These changes include a thymus which appears large, but within the normal range. Petechiae that may be present in the thymus, lungs and brain. A larynx that may exhibit a moderate amount of subacute inflammation. And small flat adrenals which may be normal for this age (Marlow, 1973).

Possible causes for SIDS which have been developed are; accidental aspiration of gastric contents causing laryngospasm, bacteremia, acute spinal injury and allergy to milk or some other substance (Marlow, 1973). However, more physicians are starting to believe that these unfortunate deaths are almost always a result of a sudden and very acute viral infection of the respiratory tract, an unknown inborn error of metabolism, laryngospasm or failure of cardiac conduction (Marlow, 1973).

Moreover, there is support for the now widely held belief that death in these babies results from instantaneous interruption of some basic physiologic function, most likely of the central or autonomic nervous system, which interferes with control of respiratory or cardiac action and results in apnea and/or extreme bradycardia or in ventricular fibrillation (Valdes-Dapena, 1979). Investigation into these possibilities is being performed, so that susceptible children can be recognized and be enabled to survive the "danger period" in early infancy through the suitable monitoring and support (Valdes-Dapena, 1979).

Although evidence is not conclusive, Sudden Infant Death Syndrome may be a sleep disorder. The relationship with sleep is suggested because most SIDS deaths happen during the night or nap time. The suggestion of the death taking place during sleep is raised because most often it is reported that no crying was heard at the time of death (Caldwell, 1995). It is implied that SIDS may be related to sleep through numerous observations. It is known that the ability to react to low oxygen levels in the blood is reduced during Rapid Eye Movement (REM) sleep and the percentage of REM sleep is much higher in young infants than it is in older children and adults (Caldwell, 1995). Moreover, it is known that sleep disturbances, including apnea, are more common in premature infants (Caldwell, 1995). The only constant finding made when babies who are victims of SIDS are carefully examined at autopsy is small groupings of fresh bruises, microscopic areas of bleeding, on the lungs and the lining of the heart (Caldwell, 1995). This suggests that the last mechanism for SIDS is exactly the same as that of choking spells or blocking of the upper airway because the same patterns are found. Although these theories have been developed, decisive evidence linking SIDS to a sleep disorder is lacking. Much of the clinically observed information simply does not fit the hypothesis and the suspicion is that the phenomenon is much more complicated than a simple sleep disorder, though it may occur during sleep (Caldwell, 1995).

A serious problem when it occurs during sleep which is receiving increased attention is gastroesphageal reflex (GER) or return of the stomach's contents to the esophagus. This incident has been attributed to inappropriate relaxation of the lower esophageal sphincter (Williams, 1988). When this occurs, it is normally primary peristalsis which then clears the esophagus. In ten healthy adults who were studied, wakefulness or at least partial arousal seemed to be an essential requirement for GER to occur (Williams, 1988). Yet, in another group of 55 infants who were studied, GER frequently took place in active sleep, but was absent in quiet sleep. This leads to suggestions in medical literature that GER may lead to apnea in some children who had been discovered to be "near miss" victims of SIDS. Therefore, researchers started monitoring esophageal pH changes in the infants (Williams, 1988). Before it can be identified as a cause of SIDS, extra work in understanding the importance of GER is required.

The identification of reduced activity of phosphoenolpyruvate carboxykinase (PEPCK) in the liver is another encouraging advance in the ongoing effort to understand Sudden Infant Death Syndrome (Hug, 1979). PEPCK is an important enzyme in hepatic gluconeogenesis. In a group of SIDS victims, hepatic PEPCK activity was on average reduced to twenty five percent of the normal level. The hypothesis is that infants susceptible to SIDS perform normally with twenty five percent of the PEPCK until confronted with a stressful situation, such as an infection with a disturbance of feeding pattern (Hug, 1979). The child may then respond with a decrease of hepatic glycogen and a reliability on gluconogenesis to preserve the levels of glucose. Fatal hypoglycemia could be the result of the inability to retain sufficient blood glucose levels at times of stress (Hug, 1979).

Some researchers believe that the only prevention for this horrible experience is close medical supervision of children in the age group which is affected (Marlow, 1973). Yet, the results of some recent studies have started to separate numerous risk factors which, though not causes of SIDS in and of themselves, might play a role in some cases (The SIDS Network, 1997) Other researchers believe that there are things which parents can do to help hinder this unfortunate event from happening. These are some tips for parents to help prevent SIDS (Caldwell, 1995):

1. Babies should not be allowed to sleep face down. They should be put to sleep on their back, or on their side (with the lower arm well forward so the infant will not roll forward onto their front).

2. Don't smoke during pregnancy (or any other time, for that matter). Don't smoke around infants or babies - they are entitled to a fair chance at life. If you can not stop smoking for your own sake, or for the sake of your children, then you must smoke outside.

3. Don't allow your infant to become too warm or too cold. If in doubt, check baby's temperature or the temperature of the room. This is very important during an upper respiratory infection.

4. Seek medical help if your baby is unwell. Viral infections and fevers may need less, not more, bedding and clothing.

Take a CPR course. This basic information and skill should be a prerequisite for parenting.

Although death is upsetting for any family, when an seemingly healthy child is found dead in his or her crib, it is more difficult to handle. Parents may be deeply broken and it is difficult for most of them to avoid feeling some degree of guilt. Therefore, they need continuous reassurance that they are not responsible and that neither suffocation or an obvious infection was in any way the reason for the death. When so much attention is being given to the problem of child abuse and when this is clearly not a factor in the death of an infant who has died unexpectedly, it is essential that the nature of the death be clearly identified, so that the parents are not subjected to additional mental suffering by inadvertent questions or remarks, from any source: police, ambulance drivers, hospital attendants and even the community at large (Valdes-Dapena, 1979). Siblings may have to deal with inaccurate accusations from people outside of the family, their own possible feelings of guilt and sudden overprotection from their parents.

The sudden death of a baby is shocking and this feeling may continue for an extended period of time. For this reason, throughout the United States of America and other countries, groups have been organized by parents who have had children die in this way, to support each other during the period of bereavement and to educate the public about the problem of Sudden Infant Death Syndrome. These organizations of parents provide help through the sharing of experiences and recognition that such deaths are not unique. The Sudden Infant Death Syndrome Network, Inc. is a not-for-profit, voluntary health agency whose goals are to eliminate SIDS through the support of SIDS research projects, to provide support for people who have been affected by SIDS and to raise public awareness of the issue (The SIDS Network, 1997). Furthermore, emotional support and concern from health team members is necessary for parents whose children have died as a result of SIDS.

Sudden Infant Death Syndrome is one of the most difficult and depressing events to have to deal with. It is a cruel and arbitrary fear of all parents and doctors. SIDS is defined as "a sudden and unexpected death of an infant, or young child, in which a thorough postmortem examination, and examination of the death scene, fails to demonstrate an adequate cause for death (Caldwell, 1995). Although it is believed some people are more prone to SIDS, it strikes families of all races, ethnic and socioeconomic backgrounds without warning, neither the parents or the physician can predict that something is wrong (The SIDS Network, 1997). In fact, most victims of SIDS, seem healthy preceding death. This paper has outlined the disorder of SIDS and provided some of the various characteristics of the unfortunate incident. Clearly, public knowledge of the tragic event needs to be increased, so that hopefully one day, the causes and prevention of it can be determined.


Caldwell, J. Paul. (1995) Sleep. Toronto: Key Porter Books Limited, pp. 176-179.

SIDS, suffocation, asphyxia, and sleeping position. John L. Carroll, M.D. and JDDeCristofaro, M.D., Internet, 1997. Http://sids-network.org/carroll2.htm.

What Everyone Needs to Know - Facts about Sudden Infant Death Syndrome (SIDS). The SIDS Network, Internet, 1997. Http://sids-network.org/facts.htm.

Sudden Infant Death Syndrome (SIDS) Information Web Site. The SIDS Network, Internet, 1997. Http://sids-network.org/index.html.

Reducing The Risk For SIDS - Some Steps Parents Can Take. The SIDS Network, Internet, 1997. Http://sids-network.org/risk.htm.

National SIDS Resource Center - What Is SIDS? The National Sudden Infant Death Syndrome Resource Center, Internet, 1993. Http://sids-network.org/sidsfact.htm.

Sleep Position and SIDS: Update from the American Academy of Pediatrics. Tom Keens and Carl E. Hunt, M.D., Internet, 1997. Http://sids-network.org/slppos.htm.

Sudden Infant Death Syndrome - Babies should sleep on their back!!! Wellness Web, Internet, 1997. Http://www.wellweb.com/index/QSUDDEN.HTM.

Hug, George. (1979) Section 8.15: Defects in Metabolism of Carbohydrates, Chapter Eight: Inborn Errors of Metabolism. Nelson Textbook of Pediatrics (Eleventh Edition), Philadelphia: W. B. Saunders Company, pp. 546.

Marlow, Dorothy R. (1973) Chapter Thirteen: Conditions of Infants Requiring Immediate or Short-Term Care. Textbook of Pediatric Nursing (Fourth Edition), Philadelphia: W. B. Saunders Company, pp. 359.

Valdes-Dapena, Marie. (1979) Section 26.1: Sudden Unexpected Death in Infancy (Sudden Infant Death Syndrome [SIDS]), Chapter Twenty Six: Unclassified Diseases. Nelson Textbook of Pediatrics (Eleventh Edition), Philadelphia: W. B. Saunders Company, pp. 1980-1981.

Williams, Robert L. (1988) Chapter Fourteen: Sleep Disturbances in Various Medical and Surgical Conditions. Sleep Disorders: Diagnosis and Treatment (Second Edition), New York: John Wiley and Sons, Inc., pp. 179-180.

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