Comparing asphyxia and unexplained causes of death: a retrospective cohort analysis of sleep-related infant death cases from a state child fatality review programme

Objectives: To examine the characteristics and circumstances of infants who died while sleeping or in a sleep environment and compare deaths classified as either unintentional asphyxia or an unexplained cause.

Design: A retrospective cohort study.

Setting: Data were extracted from the National Fatality Review Case Reporting System and Florida Vital Statistics databases.

Participants: Data on 778 sleep-related infant deaths occurring from 2014 to 2018 in Florida were analysed.

Primary outcome measure: Cause of death classification as unintentional asphyxia or unexplained.

Results: Overall, 36% (n=276) of sleep-related infant deaths in this study sample were classified as resulting from an unexplained cause compared with unintentional asphyxia. Most infants were reported to be in an adult bed (60%; n=464) and sharing a sleep surface with a person or animal (60%; n=468); less than half (44%; n=343) were reportedly placed to sleep on their back. After controlling for the influence of other independent variables, female sex (adjusted risk ratio: 1.36; 95% CI 1.06 to 1.74) and fully obstructed airway condition (adjusted risk ratio: 0.30; 95% CI 0.18 to 0.50) were associated with an unexplained cause of death.

Conclusions: The results of this analysis indicate that sleep environment hazards remain prevalent among infants who die suddenly and unexpectedly, regardless of the cause of death determination. While significant differences were observed for some factors, in many others the distributions of both demographic and incident characteristics were similar between unexplained deaths and those resulting from asphyxia. The results of this study support growing evidence that unsafe sleep environments contribute to all forms of sudden unexpected infant death, underscoring the need for standardising cause of death determination practices and promoting consistent, high-quality forensic investigations to accurately explain, monitor and prevent these deaths.