Sudden Infant Death Syndrome (SIDS)

In sudden infant death syndrome (SIDS; sometimes called “crib death” or “cot death”) an apparently healthy infant under one year of age dies suddenly with no advance warning. SIDS deaths are distinguished from other infant deaths by the fact that the death 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 is essentially a “diagnosis by exclusion,” one made by ruling out all other possible causes and then recognizing some distinctive patterns. There are currently no definitive diagnostic indicators that unmistakably identify recognized abnormalities in an infant sufficient to cause a SIDS death. Nevertheless, there are some biological, clinical, and historical or circumstantial markers commonly found in this syndrome, including (a) tiny red or purple spots (minute hemorrhages or petechiae) on the surface of the infant's heart, in its lungs, and in its thymus; (b) an increased number of star-shaped cells in its brainstem (brainstem gliosis); (c) clinical suggestions of apnea or pauses in breathing and an inability to return to normal breathing patterns; and (d) a peak incidence at two to four months of age declining rapidly almost to nonoccurrence beyond one year of age.

Formal identification of SIDS as a syndrome—an identifiable constellation of events arising from an unknown cause—and its recognition by the World Health Organization as an official cause of death distinguish SIDS deaths from those caused by child abuse or neglect. This confirms that nothing could have been done ahead of time to prevent the death.

Incidence

During most of the 1980s and the early 1990s, SIDS accounted for the deaths of 5,000 to 5,500 infants each year in the United States. By 2004, however, the number of SIDS deaths had been reduced to 2,246. Nevertheless, SIDS remains the third leading cause of deaths in infancy (following congenital malformations and disorders related to short gestation and low birth weight). Approximately two-thirds of all infant deaths occur during the perinatal and neonatal periods (at the time of birth and during the first 28 days of life, respectively). Thereafter, SIDS is the leading cause of death in the United States among infants between 1 month and 1 year of age.

SIDS is a sudden and silent killer, often associated with sleep, but apparently involving no suffering. Characteristically, SIDS deaths show a pronounced peak in number during the colder fall and winter months of the year, especially during January through March in the United States or six months later in the southern hemisphere. Epidemiological studies suggest that SIDS may be associated with a detrimental prenatal environment, but infants at risk for SIDS cannot be distinguished from those at risk for many other health problems. In general, at-risk infants include those with low birth weight or low weight gain, as well as those whose mothers were less than 20 years of age, were anemic, had poor prenatal care, smoked cigarettes or used illegal drugs during pregnancy, or had a history of sexually transmitted disease or urinary tract infection. But none of these factors is sufficient to predict how, when, why, or if SIDS will occur.

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