A Survey of Mongoloid Births in Victoria, Australia, 1942-1957

Abstract

This epidemiological study covered the State of Victoria for the years 1942 to 1957. Its main objectives were to obtain information about mongoloid births from a well-defined population and to examine the possibility of an operative environmental factor. A total of 1134 births was traced and this is no doubt the largest homogeneous group yet enumerated. There is a characteristic curve of variation of incidence with maternal age, with increasing incidence of mongoloid births particularly after the age of 34. The distribution curve of maternal ages for mothers of mongols with bitangential and this supports previously reported findings and the suggestion that the bitangentiality is due to the operation of 2 disparate etiologies, the hereditary factor being more evident with younger mothers. There was a difference of high statistical significance, between age-standardized urban and rural incidences. Annual frequencies were not constant but varied periodically and significantly, with maxima showing a 5 to 6 year cycle. Rural peaks were less marked than urban and lagged a year behind them. Another feature was that at least 40% of mongoloid births occurred sporadically in clumps or clusters, i.e., in small groups, in restricted areas and in limited periods of time. These epidemiological findings suggest that, inter alia, there is an external injurious agent at work in the causation of mongolism and that this is characteristically infective in nature.