Sudden Infant Death Syndrome (SIDS)

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Sudden Infant Death Syndrome (SIDS)

The mysterious malady

Sids research

Risk factors

back to sleep campaign

Sids in history

Support groups for parents

Resources

Sudden infant death syndrome (SIDS), also called crib death, is the death without apparent organic cause of an infant under the age of one year. The National SIDS Resource Center defines SIDS as “the sudden death of an infant under one year of age that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.” A diagnosis of SIDS can only be made after experts have investigated the death scene, autopsied the dead infant, reviewed the baby’s medical history, and ruled out all other possible explanations. Between 2,500 and 7,000 babies die of SIDS each year in the United States between the age of one week and one year, with the highest incidence from one to four months. This baffling disorder is the leading cause of death in infants ages 1 to 12 months. Although SIDS cannot be prevented completely, research has shown that parents can reduce the risk by putting their baby to sleep on its back (supine position) or side rather than on its stomach.

For unknown clinical reasons, in the United States, African American and Native American babies are up to three times more likely to die of SIDS than Caucasian infants. In all cases and groups, the majority of SIDS victims are male infants.

The mysterious malady

The SIDS definition is purposefully vague and reflects how little actually is known about what causes the syndrome. SIDS victims seem to stop breathing in their sleep. They typically are found lifeless, limp, and blue. Often they have blood-tinged mucus coming from their mouth or nose. Ninety percent of SIDS victims die before six months. Most appear perfectly healthy beforehand or at most have a slight cold. There is a statistically significant correlation between SIDS deaths and respiratory infections prior to death. Although they are usually found in their cribs, babies have died of SIDS in car seats, strollers, and their mother’s arms.

Although SIDS researchers have investigated hundreds of possible theories regarding the causes of SIDS, no clear answers have been found. Autopsies fail to show any abnormalities in SIDS victims; they seem to be healthy, normal babies. Scientists are not even sure whether death is caused by cardiac arrest or respiratory failure.

Some experts estimate that one to 20% of all diagnosed SIDS deaths are actually the result of other causes, including child abuse and murder. For this reason an autopsy and a thorough examination of the scene of death must be done. This suspicion adds to the parents’ grief and guilt. It also confuses the public’s understanding of SIDS. But until a more definitive diagnosis of SIDS exists such steps must be taken to rule out the possibility of murder.

Sids research

The age of its victims offers an important clue towards better understanding SIDS. Almost all sudden deaths occur between one week and six months of age, a time of rapid growth and change in a baby. Neurological control of the baby’s circulatory and respiratory systems is still evolving. Some scientists theorize that very subtle flaws in the baby’s physical development are responsible for SIDS. Instead of breathing evenly, young babies tend to stop breathing for a few seconds and then begin again with a gasp. According to one theory, babies who die of SIDS have difficulty re-starting their breathing. Much more needs to be known about the normal respiratory processes and sleep patterns of babies in order to detect abnormalities.

Another clue may lie in the observation that many SIDS victims have a cold in the weeks before death. SIDS deaths are more common in the winter, a season when colds are frequent. This suggests that an upper respiratory infection might somehow trigger a series of events that leads to sudden death. Some researchers believe that no one factor is responsible for SIDS but that a number of events must come together to cause the syndrome.

Risk factors

By studying large groups of young infants, a few of whom eventually go on to die of SIDS, scientists have found certain factors that occur more frequently in sudden death victims. For example, a genetic defect in an enzyme involved in fatty acid metabolism has been identified as a possible cause of death in a small percentage of SIDS victims. With this defect, the infant’s brain can become starved for energy and the baby enters a coma. Italian researchers have demonstrated a link between a particular type of irregular heartbeat and SIDS. Infants who inherit this irregularity, called long QT syndrome, are over 40 times more likely to die of SIDS. This syndrome also is a leading cause of sudden death in adults. It is possible to screen for this irregularity with heart monitors and to treat it with drugs.

Babies born prematurely are at greater risk for SIDS. So are twins and triplets. A twin is more than twice as likely as a non-twin to die of SIDS. Boys are more susceptible than girls. Formula-fed infants are more susceptible than breast-fed babies. SIDS also is more common in the babies of mothers who are poor, under 20 years old, have other children, and receive little medical care during pregnancy. Mothers who smoke during pregnancy and the presence of cigarette smoke in the home after birth also increases the likelihood of SIDS. Other proposed risk factors including childhood vaccines and allergies to cow’s milk have failed to show any link to SIDS.

It is important to remember that more than two-thirds of SIDS cases occur in babies without known risk factors. Some scientists believe that all infants are potential victims if certain factors in their bodies and their environment interact in a particular unknown way. By studying risk factors researchers hope to gain important insights into the causes of the syndrome.

In general, SIDS does not appear to be hereditary. Siblings of SIDS victims have only a slightly higher risk of sudden death compared to the average population. Yet some parents who have a subsequent baby after suffering the loss of a baby to SIDS find it very reassuring to use a home monitor. Attached to the baby, this machine sounds an alarm if the baby’s respiration or heart rate drops below normal. The National Institutes of Health has stated that home monitors have not been shown to prevent SIDS.

back to sleep campaign

SIDS occurs more frequently in New Zealand and the United States than in Japan and China. Within the United States, it is more common in African-American babies than Hispanic babies. These differences suggest that certain cultural factors of baby care, particularly how an infant is put to bed, may affect the incidence of SIDS. Scientists do not understand exactly why these differences matter—just that they do.

The single most important thing a parent or care-giver can do to lower the risk of SIDS is to put the baby to sleep on its back or side rather than on its stomach. In 1992, the American Academy of Pediatrics recommended placing healthy infants to sleep on their backs or sides. The group made the recommendation after reviewing several large studies done in New Zealand, England, and Australia. The studies demonstrated that SIDS declined as much as 50% in communities that had adopted this sleeping position for infants. In the United States, the Back to Sleep campaign has been very successful and, as of 2006, appeared to have contributed significantly to a sharp drop in SIDS in the past fifteen years. However, it also may have resulted in an increase in misshapen head syndrome, caused by infants always sleeping on their backs. This syndrome is readily treatable with physical therapy.

In the past, the supine (or back-sleeping) position has been discouraged for fear that a sleeping infant might spit up and then suffocate on its own vomit. A careful examination of studies of infants placed prone (on their stomachs) has shown that this does not happen. Some infants with certain health problems might best be placed prone. Parents who suspect this problem should check with their doctor.

Sids in history

The phenomenon of sudden death in babies has been recorded for centuries. SIDS has been described as a distinct disorder for nearly one hundred years. In 1979, it was officially accepted as a cause of death. The current definition of the condition was developed by the National Institutes of Health in 1989.

As sleeping habits for families and babies changed over time so have the explanations offered for sudden death. Until one hundred years ago, infants and small children slept in the same beds as their mother. When babies were found dead, their mothers were often blamed for rolling on top of them. In the 1700s and 1800s, mothers were accused of rolling on their babies while drunk. After noting that SIDS is very rare in Asian countries where parents and babies typically sleep together, some recent researchers have theorized that sleeping with a parent might help regulate an infant’s respiration and thus prevent SIDS.

In the early 1900s, in the United States when co-sleeping became rare, sudden death was blamed on dressing a baby too warmly at night. Before physicians realized that all babies have large thymus glands, enlargements of the thymus gland were also blamed for SIDS.

Studies released in 2003 showed no correlation between immunization schedules and SIDS death. This conclusion continues to be valid in 2006.

Support groups for parents

Parents who suffer the loss of a child to SIDS typically feel immense sorrow and grief over the unexpected and mysterious death. They also may feel guilty and blame themselves for not being more vigilant although there was nothing they could have done. Parents and other relatives of SIDS victims often find it helpful to attend support groups designed to offer them a safe place to express their emotions.

Everyone affected by the death of a baby to SIDS may need special support. This includes doctors, nurses, paramedics, other health care providers, police officers, and the babysitter or friend who may have been caring for the baby when it died. Ideally, counseling should be made available to these people. Health care professionals and law enforcement officers often have special training to help comfort the grieving survivors of a SIDS death.

Sleeping with the baby, not drinking coffee during pregnancy, using pacifiers, reducing fumes, breast-feeding, and numerous other theories have been proposed to minimize SIDS. However, as of 2006, there had been no proven cause of, or reason for, sudden infant death syndrome. Many common sense and practical recommendations have been made to reduce the risk of SIDS. All parents with small children should heed these recommendations and take all logical measures to safeguard their infants as best as possible.

See also Neuroscience; Sleep disorders.

Resources

BOOKS

Bvard, Roger W. Sudden Death in Infancy, Chldhood, and Adolescence. Cambridge, UK: Cambridge University Press, 2004.

Bvard, Roger W., and Henry F. Krous, eds. Sudden Infant Death Syndrome: Problems, Progress, and Possibilities. London, UK: Arnold, 2001.

U.S. Department of Health and Human Services. Infant Sleep Positions and SIDS: Questions and Answers for Health Care Providers. Bethesda, MD: National Institute of Child Health and Human Development, 2003.