Differentials of gestational diabetes mellitus between the Australian Aboriginal and the rest of the population
by
Maged Ishak
University of Technology, Sydney
Coauthors: Peter Petocz, University of Technology, Sydney

Background: Diabetes Mellitus is a significant health problem among the Aboriginal population in Australia. They experience a dramatically higher prevalence of this disease, estimated to be about 2.5 times higher than the non-aboriginal population [1][2][3]. In particular, gestational diabetes mellitus (GDM) and its implications on birth outcomes is a great source of concern for Aboriginal Australians. The prevalence of GDM, its development over time and the associated risk factors in the Aboriginal community have not been often and comprehensively investigated. In addition, no comparative analysis has been undertaken between the prevalence and trend of GDM in Australian Aboriginal community and in other native communities in Canada, New Zealand and the USA, which show a significantly higher prevalence of GDM, and associated higher risk of adverse health conditions for mothers and babies [10][11][12][13][14]. The objective of this present study is to examine GDM prevalence and its trend over the last 12 years among Aboriginal people, and to make comparisons with the non-Aboriginal population, using the rich population-based data of confinements in South Australia. This study aims to answer the following three questions: (1) On the basis of such a large data set from South Australia, what would be a reliable estimate of GDM prevalence in Australian Aborigines country-wide, taking into account other estimates of GDM across different states in Australia? (2) To what extent is GDM prevalence in Aboriginal Australians higher than the rest of the Australian population, and how does it compare to the rates in Aboriginal communities of other countries? (3) Do the South Australian data confirm the trend of a decreasing prevalence of GDM in the Aboriginal community as reported by (Kim and Humphery, 1999)?

Data and Procedures: A retrospective analysis was carried out of all deliveries (230, 011) that took place in South Australia between 1988 and 1999, inclusive. Age-standardised rates of GDM were computed using the direct standardisation technique. A chi-squared test was used to check the significance of the difference in prevalence between the two populations, and this difference was reported as odds ratios. Logistic regression was used to identify the relative risk of GDM in the Aboriginal population, controlling for other potentially important factors (such as age of mother, or type of hospital). Generalised linear models were used to examine the time trends in the two populations by using the computed GDM rates for each year from 1988 to 1999 for Aboriginal and non-Aboriginal people.

Results: 1. The age standardised GDM rate for Aboriginal mothers is more than 2.5 times higher than for non-Aboriginal mothers 2. There is no evidence of any significant change (definitely no decrease as some studies suggested) in this trend over the last 12 years.

Conclusion: It seems to be very clear that the prevalence of GDM, however it is measured or defined, in the Aboriginal community is significantly higher than the rate in the non-Aboriginal community in Australia with no evidence that the gap between the two population is declining.

Implications: Appropriate public health programs such as universal screening for GDM conditions and health promotion procedures should be focused on the Aboriginal community.

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Date received: April 29, 2002