Abstract â–¡ 26

Background: Increased rates of SIDS have been reported in siblings of SIDS (SSIDS) and significant physiologic differences have been observed in some SSIDS and parents of SIDS (PSIDS). Many epidemiological studies have been criticized, however, and other physiologic studies have not shown significant differences. To address these questions, a quantitative analysis was conducted of all published control studied in 1970-98.

Results: Sixty-one categories were found among 7 epidemiological and 38 physiologic studies. Mean relative risk (RR) for recurrent SIDS based just on the three best-designed studies with high autopsy rates was 5.2 (range 3.6-6.0). Systematic reviews of case histories and scene investigations were missing from these reports and the extent to which fatal child abuse may have occurred is unknown. One or more significant physiologic differences in SSIDS was documented in 20/36 categories of assessment (56%), including 6/6 reports of deficient sleep arousal responsiveness. Studies in PSIDS observed significant physiologic differences related to cardiorespiratory control in 6/14 categories (43%). Some of the negative physiologic studies may be related to type II errors or to misclassification of fatal child abuse as SIDS. Common genetic influences are suggested by these physiologic abnormalities and by a theoretical analysis of familial aggregation and risk factors.

Conclusions: SSIDS appear to have an increased RR for recurrent SIDS (mean 5.2). The clinical significance of this increase is unclear since 99.6% or more of SSIDS would currently be unaffected. The physiologic abnormalities present in some SSIDS, especially impaired arousal responsiveness, may interact with epidemiological risk factors. New insights into fatal child abuse will likely require enhanced compliance with infant-specific autopsy and death scene mandates and expert reviews of all sudden, unexpected infant deaths, including the medical history.