Nc death certificate

ABBREVIATIONS. SIDS, sudden infant death syndrome.

The American Academy of Pediatrics Task Force on Infant Positioning and SIDS issued its first recommendation on the nonprone positioning of infants in June 1992. (1) At the time the Task Force issued their statement, prone positioning of infants was the predominant mode of placement of infants to sleep in the United States. (2) Reasons for prone positioning of infants included avoiding the likelihood of aspiration. (1) Despite the common belief that infants who lie supine might be at greater risk for aspiration, the task force could find no objective data to support that belief. Thus, the task force moved forward in making its recommendation for nonprone positioning. Now, almost 9 years after the initial recommendations for nonprone positioning, the question remains whether there is a relationship between, in particular, supine positioning and aspiration-related deaths.

Another issue relating to the recommendation of nonprone positioning and the observed decrease in sudden infant death syndrome (SIDS)-related deaths (3) is whether there has been any major reclassification of SIDS deaths to other causes that might account for the drop in SIDS rates. Theories that account for the protective mechanism of nonprone positioning include a decrease in the likelihood of rebreathing and suffocation in the nonprone position. (3) Reclassification of SIDS deaths to causes related to suffocation and asphyxia could then account for some of the decrease in SIDS mortality.

The purpose of this analysis was to review changes in mortality associated with aspiration and other causes to which SIDS-related deaths might have been reclassified since the recommendations for nonprone positioning of infants for sleep were made in 1992.

METHODS

Data were obtained from linked birth and infant death statistic tapes for the United States for the years 1991, 1995, and 1996. In addition, US vital statistic natality and mortality tapes were used for the years 1992, 1993, and 1994 because of the absence of linked files for those years. For the years in which linked files were not available, denominator data (number of births) were obtained from the natality tapes and numerator data (underlying cause of death) were obtained from mortality tapes. The International Classification of Disease, Ninth Revision (ICD-9) codes for underlying causes of death that were investigated included the following: SIDS (7980), aspiration (E911), asphyxia (7990), respiratory failure (7991), and accidental suffocation in bed/cradle (E913.0). Additional broad categories of underlying causes of death were formed to determine the major causes of death replacing the drop in the SIDS proportionate mortality ratio. These broad categories included the following: infection (1011-1399), neoplasms (1400-2399), endocrine disorders (400-2799), hematologic disorders (2800-2899), mental disorders (2900-3199), neurologic disorders (3200-3899), circulation disorders (3900-4599), respiratory disorders (4600-5199), gastrointestinal disorders (5200-5799), genitourinary disorders (5800-6299), birth complications (6300-6769), dermatologic disorders (6800-7099), musculoskeletal disorders (7100-7399), congenital anomalies (7400-7599), perinatal disorders (7600-7799), ill-defined conditions (7800-7999), and injury-related disorders (E800-E999).

Demographic and infant birth information were used from the 1995 and 1996 linked file data to examine the differences in characteristics of infants who died of SIDS compared with infants who died of suffocation. Information used from the linked birth certificate file included maternal race, age, education, parity, birth number, smoking status, and infant birth weight.

Only infants who weighed 500 g or more were used in the analyses. Postneonatal mortality was defined as infant deaths that occurred at 28 days or more of life, and postneonatal mortality rates were calculated by dividing postneonatal deaths by the number of live births. Proportionate mortality ratios were calculated by dividing the number of postneonatal deaths for a specific underlying cause of death by the total number of postneonatal deaths and then multiplying by 100 to obtain a percentage of total mortality. Significant trends in postneonatal mortality rates and postneonatal mortality ratios over time were determined using [chi square] tests for trends. Logistic regression was used to determine significant independent population characteristics of infants who died of SIDS compared with infants who died of suffocation. All analyses were run in SAS (SAS, Inc, Cary, NC). P [less than or equal to] .05 was arbitrarily selected as the level indicative of statistical significance.

RESULTS

Postneonatal mortality decreased 21.9% during the 6-year period (1991-1996) from 319 postneonatal deaths per 100 000 livebirths to 249 (P < .001; Table 1). The SIDS postneonatal mortality rate declined 38.9% from a rate of 118 deaths per 100 000 livebirths in 1991 to 72 in 1996 (P < .001). In addition, the neonatal SIDS mortality rate, which composes only 6% of the total SIDS rate, declined approximately 28% from 0.07 deaths per 1000 livebirths in 1991 to 0.05 in 1996. This suggests that there has been no shift to an earlier age of death for SIDS. Postneonatal aspiration-related deaths declined significantly during the 6-year period from 1.39 postneonatal deaths per 100 000 live births in 1991 to 0.93 in 1996 (P = .01). The trend in postneonatal deaths attributed to suffocation in a bed or a cradle increased from 2.82 postneonatal deaths per 100 000 live births in 1991 to 3.26 in 1996 but failed to reach statistical significance (P = .056). There were no significant trends in postneonatal mortality for deaths attributed to asphyxia or respiratory failure.

The proportion of the postneonatal mortality accounted for by SIDS declined from 37.1% in 1991 to 28.8% in 1996 (P < .001; Table 2). This represents an 8.3% decline in the proportion of the postneonatal mortality contributed by SIDS during this time period. Of the causes of death for which SIDS might be reclassified, only suffocation in bed or cradle showed a significant increase in its proportion of postneonatal mortality (P < .001). Altogether, the causes of death to which SIDS might be reclassified accounted for <2% of the postneonatal mortality annually during the 6-year period. Approximately 93% of the 8.3% decline in the SIDS postneonatal proportionate mortality ratio was accounted for by increases in the postneonatal proportionate mortality ratios for congenital anomalies, injuries, ill-defined conditions, disorders of circulation, disorders of the digestive system, and suffocation.

The only alternative underlying cause of death to which SIDS might be reclassified that demonstrated an increase in the postneonatal proportionate mortality ratio was death by suffocation. The differences in population characteristics between infants who died of suffocation and SIDS thus were examined. Logistic regression was used to identify population characteristics independently associated with infants who died of SIDS compared with infants who died of suffocation. Characteristics examined included maternal race, age, education, parity, birth number, smoking status, and infant birth weight. Only maternal race and smoking status were significantly different between the 2 groups. Thirty percent of infants who died of SIDS were black compared with 21% of infants who died of suffocation. The adjusted odds ratio for being black and dying of SIDS was 1.61 (95% confidence interval: 1.17-2.21). Thirty percent of mothers of infants who died of SIDS reported smoking cigarettes during pregnancy compared with 39% of mothers of infants who died of suffocation. The adjusted odds ratio for being an infant who died of suffocation and whose mother smoked compared with being an infant of a smoker and dying of SIDS was 1.36 (95% confidence interval: 1.02-1.81).

DISCUSSION