Factors associated with age of death in sudden unexpected infant death

Aim This study aimed to systematically analyse the pregnancy, birth and demographic-related factors associated with age of death in sudden unexpected infant death (SUID). Methods Data were analysed from the Centers for Disease Control and Prevention's Cohort Linked Birth/Infant Death data set (2011-2013; 11 737 930 live births). SUID was defined as deaths from sudden infant death syndrome, ill-defined causes, or accidental suffocation and strangulation in bed. There were 9668 SUID cases (7-364 days; gestation >28 weeks; 0.82/1000 live births). The odds of death at different ages were compared to determine which variables significantly affect the SUID age of death. Results Forty-three features indicated a significant change in age of death with two main patterns: (a) younger chronologic age at death was associated with maternal smoking and factors associated with lower socio-economic status, and (b) older age was associated with low birthweight, prematurity and admission to the neonatal intensive care unit. However, when age was corrected for gestation, these factors were associated with younger age. Conclusion Factors that varied with age of death are well-documented risk factors for SUID. The majority of these risk factors were associated with younger age at death after allowing for gestational age at birth.