A Statistical Update on SIDS
by Stuart Tomares, M.D. (10/29/96)
SIDS, Sudden Infant Death Syndrome, is the number one cause of death between the ages of 1 month and 1 year. SIDS still accounts for approximately one-third of all deaths in the first year of life – including neonatal deaths. On October 11th, 1996 the Centers for Disease Control in Atlanta released a report on Sudden Infant Death Syndrome outlining statistical data for the years 1983-1994 (the last year that complete data are available). These data showed several important trends and offered a few interesting interpretations.
The SIDS Rate
First and foremost, the rate of SIDS, defined as the number of cases per 100,000 live newborns, dropped three times faster during the years 1990-1994 than during the years 1983-1989. During the first period (1983-1989) there were 61,882 SIDS deaths recorded and the overall SIDS rate dropped at a rate of about 1.6% a year. Between 1990 and 1994, the SIDS rate dropped at an average rate of 5.6% per year. Overall, the SIDS rate was 13.9% lower during the latter time period.
As was expected, the data showed that the rate of SIDS was highest in infants between the ages of 1-3 months, accounting for nearly 70% of all SIDS deaths and male infants were about 50% more likely to die from SIDS than females.
The Race Factor
The drop in the SIDS rate for black infants lagged behind that of whites; the SIDS rate dropped 10.4% for blacks and 16.7% for whites. The overall SIDS rate for black infants was 2.0 and 2.2 times that for white infants during the two time periods, respectively. This gap has been widening as the rate for white infants falls faster than that of blacks.
The CDC data also showed that decreases in the SIDS rate were greatest in the West and Northeast and smallest in the South and Midwest. During the first period (1983-1989) infants in the Midwest were 2.4 times more likely to die of SIDS than those in the Northeast. During the latter period, this gap widened to 2.6.
Interpreting the Findings
First of all, we can see clear evidence that the overall rate of SIDS is declining. Although complete data is not available, the preliminary findings are that the rate of SIDS is continuing to drop since 1994. This drop may be due to one of two things – either the actual number of babies dying of SIDS (a reflection of risk-factor intervention) is down or the number of infant deaths recorded as SIDS is down. Reporting criteria for SIDS deaths have been the focus of many articles in the last 5 years, emphasizing stricter adherence to autopsy protocols and and death scene investigation, perhaps influencing the rate of reported deaths independent of SIDS. Prior to 1991, an autopsy alone was the only requirement for a diagnosis of SIDS, however late in 1991, the definition was changed to include the requirement for a death scene investigation. This change may not have been uniformly implemented by all states, however. Because the non-SIDS infant mortality rate (beyond the neonatal period) did not change substantially during 1983–1989 and 1990–1994, changes in the diagnosis of SIDS alone do not likely account for the larger declines in the SIDS rate during 1990–1994.
More likely, the decline represents the heightened awareness of known risk factors for SIDS and an increase in SIDS risk-reduction education. The American Academy of Pediatrics recommendations to place otherwise healthy babies to sleep on their backs (since the SIDS rate is higher when babies sleep prone) was not published until 1992, despite overwhelming evidence from nearly 20 countries that this was a major risk factor. By 1994, the NIH began promoting the "Back to Sleep" campaign strongly suggesting that healthy infants be placed on their backs to sleep. Also, the large 1988 NIH study of SIDS risk factors found that cigarette smoking during pregnancy was also a major risk factor – 70% of the mothers whose infants died of SIDS (out of 800 infants) had smoked during pregnancy. The effects of the finding from this study combined with an overall decrease in the rate of smoking would be expected to spill over into and further reduce the SIDS rate.
Other risk factors for SIDS, not so easily affected by education, include low-birth weight, poor prenatal care, low socioeconomic status, young maternal age and lack of breast feeding. These factors likely explain the race gap in the CDC data. blacks are more likely affected by poverty and thus less likely to be exposed to physicians and educational materials – as well as being less exposed to prenatal and perinatal healthcare. There is also, currently, a higher rate of cigarette smoking in the black community.
Despite the positive aspects of the CDC data, there is much to be done. The decline in the SIDS rate is encouraging, yet still, thousands of infants die each year. The drop in the prone sleeping position is wonderful, yet the prone rate in 1994 was 43% (compared to (78% two years earlier). This is still shy of ideal, considering that the prone rate in places such as New Zealand is as low as 4%. Also, educational programs are not reaching those most affected by risk factors, the low socioeconomic status groups. Risk reduction education must continue to be emphasized and programs need to be implemented that enable widespread dissemination of risk reduction information within the black (and Hispanic) communities and to all parents.
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