BED SHARING, SMOKING, AND ALCOHOL IN THE SUDDEN-INFANT-DEATH-SYNDROME

Objectives-To investigate why sharing the bed with an infant is a not consistent risk factor for the sudden infant death syndrome in ethnic subgroups in New Zealand and to see if the risk of sudden infant death associated with this practice is related to other factors, particular ly maternal smoking and alcohol consumption. Design-Nationwide case-co ntrol study. Setting-Region of New Zealand with 78% of all births duri ng 1987-90. Subjects-Home interviews were completed with parents of 39 3 (81.0% of total) infants who died from the sudden infant death syndr ome in the postneonatal age group, and 1592 (88.4% of total) controls who were a representative sample of all hospital births in the study r egion. Results-Maternal smoking interacted with infant bed sharing on the risk of sudden infant death. Compared with infants not exposed to either risk factor, the relative risk for infants of mothers who smoke d was 3.94 (95% confidence interval 2.47 to 6.27) for bed sharing in t he last two weeks and 4.55 (2.63 to 7.88) for bed sharing in the last sleep, after other confounders were controlled for. The results for in fants of non-smoking mothers were inconsistent with the relative risk being significantly increased for usual bed sharing in the last two we eks (1.73; 1.11 to 2.70) but not for bed sharing in the last sleep (0. 98; 0.44 to 2.18). Neither maternal alcohol consumption nor the therma l resistance of the infant's clothing and bedding interacted with bed sharing to increase the risk of sudden infant death, and alcohol was n ot a risk factor by itself. Conclusion-Infant bed sharing is associate d with a significantly raised risk of the sudden infant death syndrome , particularly among infants of mothers who smoke. The interaction bet ween maternal smoking and bed sharing suggests that a mechanism involv ing passive smoking, rather than the previously proposed mechanisms of overlaying and hyperthermia, increases the risk of sudden infant deat h from bed sharing.