Abstract â–¡ 27

Background The extent to which risks for recurrent infant mortality in families are increased for non-SIDS causes has been uncertain and seldom studied. To address these questions, a quantitative analysis was conducted of all published control studies of recurrent SIDS and non-SIDS infant mortality in 1970-98.

Results Among 7 epidemiological studies of recurrence in siblings of a prior SIDS (SSIDS), 4 also analyzed the specificity of risk for recurrent infant mortality. Trends toward higher postperinatal death rates and total infant deaths in SSIDS were not significant in 2 studies. A third study showed that SSIDS were at significantly increased relative risk for birth-related deaths (RR 4.3) as well as SIDS (RR 5.8). The recurrence risks were significantly elevated for all non-infectious causes of infant death, including early/late stillbirth (p<0.001), birth-related deaths (p<0.001), congenital malformations (p<0.001) and other causes (p<0.007). The RR was 9.1 for concordance of cause of recurrent death versus 1.6 for a discordant cause of death. In the fourth study, the RR for all recurrent postperinatal infant mortality was increased to a comparable and statistically significant degree in sibling pairs whether the index & recurrence diagnoses were SIDS & SIDS (6.0) or non-SIDS & non-SIDS (7.2). There were no physiologic studies in siblings or parents of non-SIDS infant deaths.

Conclusion An increased RR for recurrent infant mortality may not be unique to SIDS. This suggests interactions between common environmental and genetic factors in affected families, at least some of which may apply to SIDS as well as non-SIDS deaths. Future studies in families with infant death from SIDS and from noninfectious non-SIDS causes need to be performed to clarify the extent of genetic risk factors and the nature of interactions with environmental risk factors. For all causes of (recurrent) infant mortality, the imperative remains to accurately distinguish natural causes from fatal child abuse and to complete a comprehensive postmortem evaluation that includes not only the standardized autopsy but also a thorough review of the case history and a timely, sensitively-conducted scene investigation.