‘Summer is here, fraught with death to hapless babes’: the seasonality of infant mortality in late nineteenth-century Tasmania

Rebecca Kippen, University of Melbourne

This study investigates the seasonality of infant mortality in nineteenth-century Tasmania using a unique computerised database containing all civil birth and death registration records for Tasmania from 1838 to 1899. The individual-level records allow the computation of cause-specific infant mortality rates, as well as rates by age at death (in days) and month of death. Infant mortality averaged around 90–110 deaths per 1,000 births from 1860 to the end of the century, while mortality at other ages steadily declined. Persistently high infant mortality was probably caused by infantile diarrhoea. This argument is borne out by the seasonal pattern of infant mortality, which remained stable over this period, and which consisted of a strong peak in January, February and March, and lower levels of mortality in the colder months. The seasonal patterns of other commonly registered causes of infant death—such as ‘Convulsions’, ‘Debility and marasmus’ and ‘Teething’— suggests that they subsumed many cases of infantile diarrhoea. Infant mortality under the age of ten days exhibited very little seasonality, and what there was followed birth seasonality very closely, indicating that the incidence of death soon after birth was not influenced by the month of birth. Infant mortality became more seasonal as age at death increased, also suggesting diarrhoeal disease as a cause of death, since older weaned infants were more susceptible to diarrhoeal disease.

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Presented in Session 85: Historical epidemiology