Undiagnosed metabolic dysfunction and sudden infant death syndrome--a case-control study.

BACKGROUND: Decades of research has yielded few clues about causes of sudden infant death syndrome (SIDS). While some studies have shown a link to inborn errors of metabolism (IEMs), few have examined the link in a large population-based sample. This population-based case-control study assessed the association between undiagnosed IEMs and SIDS.

METHODS: Children born in California during 2005-08 who died from SIDS were obtained from death records and linked to the newborn screening, birth certificate, and hospital discharge databases. Individuals with known chromosomal and neural tube defects, genetic disorders, and non-singleton births were excluded. Five controls were matched to each case on tandem mass spectrometry testing date and lab code. Rates of undiagnosed IEMs were compared between cases and controls using conditional logistic regression adjusting for known confounding factors.

RESULTS: After adjusting for known confounding factors, SIDS cases had similar risk of having IEMs as controls (adjusted hazard ratio [HR] 1.3, 95% confidence interval [CI] 0.3, 5.5). Infants who were male, Black, and born preterm had higher risk of SIDS with the highest risk observed for those born preterm [adjusted HR = 1.7, 95% CI 1.3, 2.2]. Younger maternal age at delivery, mother being born in the US, parity after current birth >3, and delayed prenatal care were also significantly associated with higher risk of SIDS.

CONCLUSIONS: While many maternal and infant factors are associated with an increased risk of SIDS, there is no evidence that undiagnosed IEMs are associated with increased risk.