The prevalence of diabetic complications is reported from a cross-sectional study of rural diabetic subjects in Western Australia. Logistic-regression analysis has been used to discover potential risk factors associated with each complication. A distinction has been made between time-related variables (age, age at diagnosis, duration of diabetes) and other risk variables. We have attempted to identify the major time-related risk variables for each complication and then examined the effect of other risk variables after accounting for the major time-related variables. The important time-related variables were found to be duration of diabetes for retinopathy, age for macrovascular disease, duration and age at diagnosis of diabetes for sensory neuropathy, and age for renal impairment. When matched on these important time-related variables, the overall prevalences of complications for insulin-dependent (IDDM) compared with non-insulin-dependent (NIDDM) diabetic patients were essentially the same. An exception is renal impairment, for which IDDM patients had a higher prevalence than did NIDDM patients of the same age. After allowing for time-related variables, the analysis also demonstrates positive independent associations between diabetic control (glycosylated hemoglobin) and retinopathy and between diabetic control and macrovascular disease. Plasma cholesterol (positively) and high-density lipoprotein cholesterol (negatively) were related independently to both macrovascular disease and renal impairment. Very few differences in the risk-factor profiles for complications were found for IDDM compared with NIDDM patients after allowing for time-related variables.

The major histocompatibility complex (MHC) contains multiple and diverse genes which may be relevant to the induction and regulation of autoimmune responses in insulin dependent diabetes mellitus (IDDM). In addition to HLA class I and II, the possible candidates include TNF, C4, and several other poorly defined polymorphic genes in the central MHC region. This study describes two approaches which take advantage of the fact that the relevant genes are carried by highly conserved ancestral haplotypes such as 8.1 (HLA-B8, TNFS, C4AQ0, C4B1, DR3, DQ2). First, three "diabetogenic" haplotypes (two Caucasoid and one Mongoloid) have been compared and it has been shown that all three share a rare allele of BAT3 as well as sharing DR3, DQ2. In 43 sequential patients with IDDM the cross product ratio for BAT3S was 4.8 (p less than 0.01) and 6.9 for HLA-B8 plus BAT3S (p less than 0.001). Second, partial or recombinant ancestral haplotypes with either HLA class I (HLA-B8) or II (HLA-DR3, DQ2) alleles were identified. Third, using haplotypic polymorphisms such as the one in BAT3, we have shown that all the patients carrying recombinants of the 8.1 ancestral haplotype share the central region adjacent to HLA-B. These findings suggest that both HLA and non-HLA genes are involved in conferring susceptibility to IDDM, and that the region between HLA-B and BAT3 contains some of the relevant genes. By contrast, similar approaches suggest that protective genes map to the HLA class II region.

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We confirm microalbuminuria as an independent predictor of mortality in type 2 diabetes despite its association with a number of conventional cardiovascular risk factors.