Diabetes and glucose tolerance in New South Wales coastal Aborigines: possible effects of non-Aboriginal genetic admixture.

A survey of adults living in two predominantly Aboriginal communities in eastern New South Wales revealed a crude prevalence of clinically diagnosed diabetes of 6.7% in Aboriginals. 1.4% of Aboriginal subjects investigated with 75 g oral glucose tolerance tests were found to have previously undiagnosed diabetes, and 2.8% had impaired glucose tolerance. 53% of women and 27% of men were obese as judged by body mass index. The age-sex standardised prevalence of diabetes in Aboriginals (previously diagnosed and newly detected) was 7.8%, which is substantially lower than the 15.6% prevalence found in the Aboriginal population of Bourke (central New South Wales). HLA antigen studies on these same individuals suggest approximately 60% genetic admixture from non-Aboriginal sources. Insulin response to oral glucose and mean body mass index were both related to non-Aboriginal genetic admixture with higher values in Aboriginal subjects than in their non-Aboriginal neighbours, and highest values were found in those with no detectable non-Aboriginal HLA haplotypes. The extent of genetic admixture in these communities may partly explain the lower prevalence of diabetes when compared with that found in the Aboriginal population of Bourke.