Sudden infant death syndrome: factors contributing to the difference in incidence between Victoria and Tasmania.

OBJECTIVE: To examine how much of the difference in incidence of sudden infant death syndrome (SIDS) between Tasmania and Victoria could be accounted for by the effect of differing climatic temperature and the effect of the differing prevalence of maternal and infant characteristics in the two State populations. DESIGN: A two population ecological comparison. Two previously published predictive models were applied to quantify the contribution of several factors to the higher incidence of SIDS in Tasmania compared with Victoria. SETTING: A population based study involving the two Australian States of Tasmania and Victoria. PATIENTS: The characteristics of the 1985 to 1987 live birth cohorts of Tasmania and Victoria were examined. Cases were defined as all infants dying in 1985 to 1987 whose cause of death was stated as SIDS. RESULTS: The rate of SIDS for Tasmania and Victoria 1985 to 1987 was 3.76 per 1000 live births and 2.18 per 1000 live births respectively. Adjustment of the Tasmanian rate for the effect of the interstate difference in climatic temperature resulted in a lower Tasmanian rate of 2.92 per 1000 live births. Adjustment for the effect of interstate differences in maternal age, birthweight, infant sex, month of birth and intention to breast-feed at hospital discharge decreased the Tasmanian rate to 2.47 per 1000 live births. CONCLUSION: Approximately 82% of the interstate difference in SIDS incidence between Tasmania and Victoria from 1985 to 1987 can be accounted for by differences in climatic temperature, maternal age, birth-weight, infant sex, month of birth and feeding intention at hospital discharge.