Perspectives in Disease Prevention and Health Promotion Premature Mortality due to Congenital Anomalies

In 1984, congenital anomalies were the fifth leading cause of years of potential life lost before age 65 (YPLL). They accounted for 684,000 YPLL, or about 6% of all YPLL (Table V, page 105).

Presented below are data on YPLL attributable to selected types of congenital anomalies by race (white, all other). Detailed mortality computer tapes available from the National Center for Health Statistics were used. The latest year for which tapes are available is 1982. Because of the year-to-year variation in YPLL (1), yearly average YPLL is presented for 1980-1982. To show changes over time, the 1980-1982 data were compared with 1970-1972 data.

In 1980-1982, an average yearly total of 732,549 YPLL was attributed to congenital anomalies, compared with 868,679 in 1970-1972 (Table 1), a decrease of 15.7%. For whites, the decrease was 19.0%, but for other races, YPLL increased 2.3%. In 1980-1982, 80% of YPLL due to congenital anomalies is derived from infant deaths (under 1 year of age); in 1970-1972, the figure was 78%. Compared with 1970-1972, the yearly average number of births was 3.6% higher in 1980-1982--1.0% higher for whites and 15.7% for other races. Since most YPLL due to congenital anomalies is derived from infant deaths and because the average yearly number of births was higher in 1980-1982 than in 1970-1972, particularly for other races, the changes in YPLL give a somewhat misleading picture of the impact of congenital anomalies on premature mortality. Adjusted for the change in average numbers of yearly births, YPLL decreased 18.6% overall from 1970-1972 to 1980-1982--19.8% for whites and 11.5% for other races.

Congenital anomalies of the cardiovascular system were the leading cause of premature mortality, accounting for 44.7% of YPLL due to congenital anomalies in 1980-1982 and 48.1% in 1970-1972 (Table 1); there was relatively little difference between the percentages for whites and those for other races. Nervous-system defects accounted for 17.5% of YPLL due to congenital anomalies in 1980-1982, a substantial decrease from the 1970-1972 percentage of 23.1. In 1980-1982, 7.4% of YPLL due to congenital anomalies was attributed to chromosomal anomalies, compared with 3.5% in 1970-1972. An increase in the number of YPLL from 1970-1972 to 1980-1982 was also seen for congenital anomalies of the respiratory system. The number of YPLL attributed to congenital anomalies of the digestive system decreased substantially from 1970-1972 to 1980-1982. Reported by Birth Defects and Genetic Diseases Br, Div of Birth Defects and Developmental Disabilities, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: As infant mortality due to causes other than congenital anomalies has been reduced, congenital anomalies have become the leading cause of infant mortality and are the fifth leading cause of YPLL. Nevertheless, it appears that YPLL due to congenital anomalies has decreased over the past decade, despite an increase in the number of births. Much of this decline may be attributed to improvements in the care of infants born with congenital anomalies, resulting in an increased survival rate. The decline cannot be attributed to an overall decline in the incidence rate of anomalies. According to CDC's birth defects surveillance data, the rates of occurrence of most defects have remained stable over the past decade (2) with a few notable exceptions. The rates of anencephaly and spina bifida have decreased substantially, which may account for some of the decrease in YPLL due to nervous-system anomalies, and the reported rate of some types of heart defects has increased.

Although new improvements in the care of affected individuals may further reduce YPLL due to congenital anomalies, the ultimate goal is reduction by primary prevention of congenital anomalies. Primary prevention will require the discovery of the causes of congenital anomalies, which are known to operate at the time of embryogenesis and organogenesis during the first trimester of pregnancy. Primary prevention is important, since many who now survive infancy with congenital anomalies face a lifetime of debilitating morbidity.

Even though congenital anomalies are among the leading causes of premature mortality, the YPLL statistics understate their true impact. One reason is that anomalies in infants who die shortly after birth may not be diagnosed and, thus, the infants' deaths may not be attributed to congenital anomalies. Another reason for understatement is that the YPLL statistics are based only on liveborn infants. A substantial number of fetuses with anomalies, however, die in utero.

The comparison of 1970-1972 data with 1980-1982 data may be clouded to some extent by changes in diagnostic acumen and cause of death attribution and in mortality coding. The 1970-1972 data were coded for cause of death by the Eighth Revision, International Classification of Diseases (ICD-8), and the 1980-1982 data were coded by the 9th Revision (ICD-9). For some categories of anomalies, code differences are very minor, but for others, ICD-9 is more detailed. For example, the coding available for chromosomal anomalies is more extensive in ICD-9. The YPLL for chromosomal anomalies was about twofold higher in 1980-1982 than in 1970-1972. Since the incidence of the common chromosomal anomalies seems to have remained relatively stable over the past decade, and since survival has been stable or has improved, the doubling of YPLL attributed to chromosomal anomalies is likely to result from better diagnosis and cause of death attribution and/or coding.

References

1. CDC. Changes in premature mortality--United States, 1983-1984. MMWR 1986;35:29-31.

2. CDC. Temporal trends in the incidence of malformation in the United States, selected years, 1970-71, 1982-83. MMWR: CDC Surveillance Summaries, 1985;34 (No. 2SS);1SS-3SS.

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