December 10, 2019
3 min read

Study identifies two distinct subgroups of SUIDs that differ by age

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Tatiana M. Anderson, PhD 
Tatiana M. Anderson
Juan M. Lavista Ferres, MSc 
Juan M. Lavista Ferres

Cases of sudden unexpected infant death, or SUID, that occur at 0 to 6 days differ significantly from cases that occur at days 7 to 364 in regard to factors like live birth order and marital status, according to study results published in Pediatrics. Researchers suggested that the two groups be separated in future research.

“There are two different SUID populations, each with a distinct epidemiological pattern,” Tatiana M. Anderson, PhD, a PhD fellow at Seattle Children’s Research Institute’s Center for Integrative Brain Research, told Healio. “We found that the traditionally known risk factors for SUID, like being a young mother, unmarried mother or increasing live birth order, are reversed for deaths in the first week [called sudden unexpected early neonatal death (SUEND)]. Clinicians should be aware that risk factors are different for deaths that occur in the first week vs. deaths that occur after the first week.”

Anderson and colleagues performed a retrospective, cross-sectional analysis of 37,624 SUID cases reported between 2003 and 2013 from the CDC Prevention Birth Cohort Linked Birth/Infant Death Data Set. They designated SUID cases as early neonatal deaths, which included deaths at days 0 to 6, or postperinatal deaths, including deaths at days 7 to 364.

ICD-10 codes that differed among the two groups included marital status, live birth order, age of mother, birth weight and gestational length.

“SUEND rate as [a] percentage of total births has remained constant since 1983,” Juan M. Lavista Ferres, MSc, general manager for Microsoft’s AI for Good Research Lab, told Healio. “During this time, infant mortality in general has decreased, [the] smoking rate in mothers has decreased, we have advances in medicine and the SUID rate in general was cut in half, so [it] is very surprising that SUEND has remained constant.”


In the postperinatal group, increasing live birth order between the second and fifth children raised the adjusted OR for postperinatal death compared with the first live birth. Conversely, live birth order between the second and fifth children lowered the aOR for death compared with the first live birth.

The groups also differed in regard to marital status, with higher postperinatal SUID rates (aOR = 1.19; 95% CI, 1.15-1.23) among children with unmarried parents at birth. In the SUEND group, being unmarried decreased the risk for SUEND (aOR =0.72; 95% CI, 0.61-0.85).

In an accompanying editorial, Richard D. Goldstein, MD, program director for Robert’s Program at Boston Children’s Hospital and assistant professor of pediatrics at Harvard Medical School, wrote in an accompanying editorial called the study “an important contribution to the conversation” about SUID during the first week of life.

“Their efforts join other recent contributions arguing that this earliest unexplained neonatal mortality may represent something different from SIDS and its analogs,” Goldstein wrote. “At first glance, this accumulated research is reminiscent of findings that led to the demise of what was once called ‘near SIDS,’ when differences in risk factors and incidence over time led to the conclusion that apparent life threatening events, now called brief resolved unexplained events, were unrelated to SIDS.”

According to CDC estimates, approximately 3,600 deaths were attributed to SUID in 2017 alone, including 1,400 deaths caused by SIDS, 900 by accidental suffocation and strangulation and 1,300 attributed to unknown causes.

“SUEND deaths are a statistically distinct entity from postperinatal SUID deaths, and should be separated in future research,” Anderson said. “Not only will this lead to cleaner data sets with less noise, but the distinctions should provide clues for the differences in [the] underlying mechanism.” – by Eamon Dreisbach


CDC. Sudden Unexpected Infant Death and Sudden Infant Death Syndrome. Accessed December 10, 2019.

Ferres JML, et al. Pediatrics. 2019;doi:10.1542/peds.2019-1637.

Goldstein RD. Pediatrics. 2019;doi: 10.1542/peds.2019-321.

Disclosures: Anderson, Ferres and Goldstein report no relevant financial disclosures.