1. A retrospective analysis of cases of sudden unexpected infant death (SUID) found that SUIDs in the first week of life differ significantly from SUIDs in the postperinatal period (days 7-364 of age) in live birth order, marital status, age of mother, birth weight, and gestational length.
2. Cases of SUID before and after 7 days of age also differed significantly in distribution of International Classification of Diseases, 10th Revision (ICD-10) codes.
Evidence Rating Level: 2 (Good)
Study Rundown: Sudden unexpected infant death combines several ICD-10 codes and causes of death, but there may exist distinct subcategories of SUID based on the age of death of an infant. In this retrospective study, researchers used national, linked infant birth and death data from the Centers for Disease Control and Prevention (CDC) to identify cases of SUID and analyzed them for distinct subgroups based on parental and infant covariates using logistic regression models. SUIDs that occurred in the early neonatal period (<7 days of age), referred to as sudden unexpected early neonatal deaths (SUENDs), differed significantly from other SUIDs that occurred in the first year of life in distribution of ICD-10 codes, live birth order, marital status, age of mother, birth weight, and gestational length.
These findings are limited by a lack of information about postnatal risk factors for SUID, such as bed-sharing and sleeping position. Nonetheless, the study is strengthened by its comprehensive national data source encompassing every birth in the United States between 2004 and 2013. For physicians, these findings suggest that studying the two distinct populations of SUID cases separately may reveal underlying physiologic mechanisms and causes, and lead to new prevention and intervention efforts to address SUID.
Relevant reading: National and State Trends in Sudden Unexpected Infant Death: 1990–2015
In-Depth [retrospective cohort study]: Researchers used the 2003 to 2013 CDC Birth Cohort Linked Birth/Infant Death Data Set to identify 41 125 233 births and 37 624 cases of SUID, defined as infant death at <365 days old with the R95, R99, or W75 ICD-10 codes. Logistic regression models were used to compare cases of SUID at each age of death by day to analyze for differences in a variety of parental and infant covariates. Each model was constructed using 500 SUID cases that occurred on each day compared with 37 124 controls (SUID patients who did not die on that day). SUIDs that occurred between days 0 to 6 of age significantly differed from SUIDs that occurred between 7 and 364 days of age, and were referred to by the researchers as SUENDs. SUENDs differed significantly from SUIDs in diagnostic codes, live birth order, marital status, age of mother, birth weight, gestational length. Specifically, being unmarried at time of birth was associated with higher odds for SUID (adjusted odds ratio [aOR] = 1.19; 95% confidence interval [CI] = 1.15-1.23) but lower odds for SUEND (aOR = 0.72; 95%CI = 0.61-0.85). Younger mothers (ages 15-24) had higher SUID rates but lower SUEND rates.
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