Family analysis of sudden infant death syndrome: Genetic, clinical and epidemiologic risk factors

Abstract

Sudden Infant Death Syndrome (SIDS) is the leading cause of infant death between one month and one year of age. Epidemiological studies have suggested that SIDS is not a single entity, but a heterogeneous group of conditions in which some of the deaths may be preventable through increased awareness of signs indicating a vulnerable infant. The "birth score" approach, developed in England, prospectively attempts to identify newborns at risk for adverse outcome. The current retrospective study was designed to investigate the etiologic effects of environmental, cultural or genetic mechanisms on the occurrence of SIDS. Participating families provided information, via a questionnaire, regarding the pregnancy, medical and family histories for the SIDS infant. The analyses compared these data on SIDS infants with and without a positive family history of SIDS in a 1{dollar}\sp{lcub}\rm st{rcub}{dollar} or 2{dollar}\sp{lcub}\rm nd{rcub}{dollar} degree relative and among cases from different geographic regions. Genetic studies consisted of both nuclear family and complex segregation analyses. Evaluation of "birth scoring" was performed on two cohorts of children who were selected from hospital records at the University of Maryland using established birth score parameters. Analyses comparing various factors between SIDS infants based on their family history and among geographic regions revealed no significant associations. Nuclear family segregation analysis indicated that a recessive hypothesis could not be rejected as a possible explanation for approximately 2.5% of SIDS deaths occurring in this sample population. Complex segregation analysis suggested that familial SIDS was best explained by a recessive model in which p was fixed at 0.0001, there was no ascertainment correction, sex was included as a covariate and the transmission parameters were non-Mendelian. The birth score approach, based on the specific parameters used, was not as effective in identifying at-risk infants in the Baltimore population as elsewhere.;Results of this study indicate that: (1) SIDS has a measurable familial component and (2) "birth scores" need unique modification reflecting the specific population being assessed.