Overall Postneonatal Mortality and Rates of SIDS

Reductions in sudden infant death syndrome (SIDS) are commonly attributed to modifications in infant sleep environments. Approaches to diagnosis in sudden infant death, death scene investigations, the prevalence of intrinsic risk factors for SIDS, and the potential influence of treatment-related factors on infant vulnerability have also changed. Understanding all contributory factors may help reduce residual SIDS rates.

We analyzed US Mortality Multiple Causes Records for 1983 to 2012 to compare SIDS postneonatal mortality rates with a projection applying non-SIDS mortality changes, using those changes as a proxy measure for alterations in intrinsic risk. Composites of neglect-related, unknown, and circumstantial respiratory diagnoses were measured, as was a cumulative composite of unexplained infant death diagnoses. Cluster analysis with leading causes of postneonatal mortality and SIDS mortality rates for low birth weight infants were also examined.

SIDS and non-SIDS postneonatal mortality rates were concordant over time. Important variance was seen 1994 to 1996, coinciding with Back-to-Sleep initiation. Other variance, eliminated in the cumulative composite, appeared related to differences in diagnostic practices. Changes in SIDS rates resembled changes in mortality from congenital malformations, respiratory distress of the newborn, and diseases of the circulatory system. SIDS rates for low birth weight infants followed broader postneonatal trends.

SIDS mortality followed trends in overall postneonatal mortality, including effects of changes in the infant sleep environment and diagnostic classification. Preventing asphyxia risk in the sleep environment must be coupled with efforts to understand intrinsic biological pathways, some potentially associated with other categories of infant and perinatal mortality.