Perspectives in Disease Prevention and Health Promotion Premature Mortality due to Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) ranked as the seventh leading cause of years of potential life lost before age 65 (YPLL) in 1984. It accounted for 314,000 (2.4%) YPLL of the total YPLL in that year (see Table V, page 179). In 1984, SIDS accounted for 12.4% of all YPLL from deaths among infants.

Data presented below are from the National Center for Health Statistics (NCHS) Mortality Detail tapes. The latest year for which these tapes are available is 1982. Deaths were attributed to SIDS if the underlying cause of death was classified as category 798.0 in The International Classification of Diseases, 9th Revision (ICD-9), and age at death was under 1 year.

In 1979, 340,496 YPLL were attributed to SIDS; in 1980, 355,395; in 1981, 341,528; and in 1982, 340,431. The average YPLL due to SIDS for this 4-year period was 344,462. During this same period, the race- and sex-specific YPLL was 144,319 for white males; 89,752 for white females; 55,873 for black males; 44,424 for black females; 5,644 for other males; and 4,451 for other females. The male:female YPLL ratio for white infants was 1.6:1, compared with 1.3:1 for black and other infants..

YPLL is directly dependent on the number of births in any given group. The average annual YPLL per 1,000 live births is 97.2 for white males; 63.9 for white females; 187.7 for black males; 153.6 for black females; 86.6 for other males; and 72.7 for other females. Reported by Perinatal Environmental Epidemiology Br, Div of Birth Defects and Developmental Disabilities, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: SIDS is defined as the unexpected death of a previously healthy infant between 2 weeks and 1 year of age, unexplained after a complete autopsy examination (1). SIDS usually occurs during the first 6 months of life. The concept and definition of a sudden infant death syndrome were formalized in 1969, and SIDS was not specified as a cause of death until ICD-9 came into use in 1979. Therefore, comparison of YPLL due to SIDS cannot be carried out using vital records for years before 1979.

SIDS is usually a diagnosis of exclusion, theoretically dependent on the performance of a post-mortem examination. Since 1979, the autopsy rate for SIDS in the NCHS Mortality Detail tapes has exceeded 80%. This compares with an autopsy rate of approximately 40% for non-SIDS infant deaths. The higher autopsy rate for SIDS may result from legal requirements in some areas. It is important to note that the death certificate may be completed before the results of the autopsy are available.

From 1979 to 1982, the YPLL due to SIDS has ranged from 340,000 to 355,000, and the rate of death due to SIDS/1,000 live births ranged from 1.4 to 1.5. This compares with worldwide rates of 0.6/1,000 to 3.0/1,000. In 1980, NCHS recorded the highest U.S. rate of SIDS deaths. This followed the National Institute of Child Health and Human Development SIDS Cooperative Epidemiological Study, which finished interviewing parents in 1980. This may represent increased case finding stimulated by this study.

The etiology of SIDS is unclear, although there are several established risk factors (1). Current theories implicate an abnormality of the autonomic regulation of respiratory and/or cardiovascular function. Whether this is due to genetic or environmental factors, or is prenatal or postnatal in origin, is unknown. Risk factors include sociodemographic and pregnancy-related variables. Siblings of SIDS victims have a tenfold increased risk of SIDS. Blacks and Native Americans have a rate of SIDS two to three times that of whites (2). Preterm and low-birthweight infants, as well as products of multiple gestations, are also at increased risk of SIDS. In many studies, SIDS appears to be seasonal, with increased rates in the winter months (November-March), raising the speculation that respiratory infections may potentiate whatever underlying predisposition may exist.

Prevention of SIDS is hindered by lack of knowledge of the etiology and lack of understanding of which infants are at particularly high risk. Some survivors of episodes of infant apnea ("near misses") and some siblings of SIDS victims are currently being treated with home apnea monitoring and various pharmacologic therapies. The efficacy of these interventions has not been formally evaluated in a randomized clinical trial. In addition, the number of deaths that are potentially preventable using these interventions represents only a small portion of total SIDS deaths. Laboratory research on SIDS is needed to identify high-risk infants and to develop effective prevention measures.

References

1. Peterson DR. Evolution of the epidemiology of sudden infant death syndrome. Epidemiologic Rev 1980;2:97-112.

2. Adams MM. The descriptive epidemiology of sudden infant deaths among natives and whites in Alaska. Am J Epidemiol 1985;122:637-43.

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