Perspectives in Disease Prevention and Health Promotion Premature Mortality Due to Sudden Infant Death Syndrome -- United States, 1980-1986

Years of potential life lost before age 65 (YPLL) highlights the mortality trends in younger age groups, especially infants (1 year of age). In 1986, sudden infant death syndrome (SIDS) accounted for an estimated 336,884 YPLL* and ranked as the eighth leading cause of YPLL. In comparison, in 1984 and 1985, SIDS accounted for 316,909 and 313,386 YPLL, respectively, and ranked as the seventh leading cause of YPLL.

In Table V, deaths are attributed to SIDS if the underlying cause of death is classified as category 798.0 according to the International Classification of Diseases, 9th Revision (ICD-9), and age at death was 1 year. In the analysis reported here, the numbers and underlying causes of death are from the National Center for Health Statistics (NCHS) national mortality computer tapes. YPLL was calculated by averaging age at death for each subgroup** during both the neonatal period (28 days) and the postneonatal period (28 days to 1 year), for 1980-1983, the latest year for which data are available (Table 3) (1,2).

For 1980-1983, the average annual YPLL due to all causes of infant death was 2,787,465; 1,861,691 YPLL (66.8%) occurred because of deaths in the neonatal period, and 925,774 YPLL (33.2%) occurred because of deaths in the postneonatal period (2). During 1980-1983, 12.4% of the YPLL in the first year of life and 34.5% of the YPLL in the postneonatal period were due to SIDS.

The average annual YPLL due to SIDS during this 4-year period was 346,158. The average annual race- and sex-specific YPLL was 144,882 for white males; 92,057 for white females; 55,158 for black males; 43,702 for black females; 5,809 for other males; and 4,548 for other females. The male:female ratio for white infants was 1.6:1, compared with 1.3:1 for black infants and 1.3:1 for other infants. There were no discernible trends during this 4-year period (Table 3).

YPLL depends directly on the number of births in any given group. The average annual YPLL due to SIDS per 1,000 live births was 96.8 for white males, 65.0 for white females, 184.6 for black males, 150.6 for black females, 82.3 for other males, and 67.7 for other females. Reported by: Pregnancy Epidemiology Br, Research and Statistics Br, Div of Reproductive Health, Center for Health Promotion and Education, CDC.

Editorial Note

Editorial Note: SIDS and other causes of infant death consistently rank low in mortality statistics because these statistics are dominated by the underlying disease processes of the elderly. YPLL, which does not count deaths of persons 65 years or older, is an alternative method for determining the impact of particular health problems. It can quantitate these problems and thus enable public health officials to set priorities. The use of YPLL demonstrates the importance of SIDS because deaths early in life are weighted heavily in the calculation of YPLL. For comparative purposes, the total deaths attributable to SIDS for the years 1980-1983 were 5,510, 5,295, 5,278, and 5,305, respectively.

The most widely accepted definition of SIDS, proposed by Beckwith in 1968, is "the sudden death of any infant or young child, which is unexpected by history, and in which a thorough postmortem examination fails to demonstrate an adequate cause of death" (3). However, in 12% of SIDS deaths reported from 1980-1983, no autopsy was performed. Also, only children 1 year of age were included for the calculation of YPLL. Deaths that would be classified as SIDS but that occur in children greater than or equal to 1 year of age are classified as instantaneous deaths by NCHS and are coded 798.1 by ICD-9. In addition, there is no minimum age for the diagnosis of SIDS, and, in 1980-1983, 105,748 YPLL due to SIDS occurred in the neonatal period.

The male excess in YPLL due to SIDS per 1,000 live births (49% for whites, 23% for blacks, and 22% for other races) reflects the unexplained increased risk of death from SIDS in male infants (4). This may reflect the increased incidence in mortality and infectious disease morbidity in male infants (5). The largest percentage of excess in YPLL in male infants per 1,000 live births occurs in whites because the greatest relative risk of death from SIDS due to gender is in whites.

The rate of YPLL due to SIDS per 1,000 live births for blacks is 1.7 times that for whites. This is related, at least in part, to the increased incidence of low birthweight (6), teenage fertility (7), and lower socioeconomic conditions among blacks (8), because each of these risk factors independently increases the risk of death from SIDS (9-13). Closing the black-white gap depends in part on the reduction of these three risks.

References

1. CDC. Years of potential life lost attributable to low birthweight--United States, 1980 birth cohort. MMWR 1986;35:188-90,195.

2. CDC. Years of potential life lost before age 65 due to perinatal conditions--United States, 1980-1983. MMWR 1987;36:179-80,185-7.

3. Beckwith JB. Discussion of terminology and definition of sudden infant death syndrome. In: Bergman AB, Beckwith JB, Ray CG, eds. Proceedings of the Second International Conference on Causes of Sudden Deaths in Infants. Seattle, Washington: University of Washington Press, 1970.

4. Peterson DR, van Belle G, Chinn NM. Epidemiologic comparisons of the sudden infant death syndrome with other major components of infant mortality. Am J Epidemiol 1979;110:699-707.

5. Beckwith JB. The sudden infant death syndrome. Rockville, Maryland: US Department of Health, Education, and Welfare, Public Health Service, Health Services Administration, 1976:12; DHEW publication no. (HSA)76-5137.

6. Hogue CJR, Buehler JW, Strauss LT, Smith JC. Overview of the National Infant Mortality Surveillance (NIMS) Project--design, methods, results. Public Health Rep 1987;102:126-38.

7. National Center for Health Statistics. Advance report of final natality statistics, 1984. Monthly Vital Statistics Report 1986;35:17-8.

8. Bureau of the Census. Money, income of households, families, and persons in the United States: 1980. Washington, DC: US Department of Commerce, 1982. (Current population reports; series P-60; no. 132).

9. Black L, David RJ, Brouillette RT, Hunt CE. Effects of birth weight and ethnicity on incidence of sudden infant death syndrome. J Pediatr 1986;108:209-14.

10. Babson SG, Clarke NG. Relationship between infant death and maternal age. J Pediatr 1983;103:391-3.

11. Bergman AB, Ray CG, Pomeroy MA, Wahl PW, Beckwith JB. Studies of the sudden infant death syndrome in King County, Washington. III. Epidemiology. Pediatrics 1972;49:860-70.

12. Valdes-Dapena M, Birle LJ, McGovern JA, McGillen JF, Colwell FH. Sudden unexpected death in infancy: a statistical analysis of certain socioeconomic factors. J Pediatr 1968;73:387-94.

13. Froggatt P, Lynas MA, MacKenzie G. Epidemiology of sudden unexpected death in infants ('cot death') in northern Ireland. Br J Prev Soc Med 1971;25:119-34. *A projected estimate based on data from the National Center for Health Statistics Monthly Vital Statistics Report (compiled from a 10% sample of all deaths) through November 1986. **YPLL = T (65-(A-/365.25)), where T = total number of infants deaths for subgroup (year, race, sex, and cause of death) and A = average age at death in days for that subgroup.

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