Background: Type 2 diabetes (T2DM) is the leading cause of chronic kidney disease (CKD) in Australia, especially among Aboriginals.
Aim: To compare the baseline prevalence of CKD in T2DM in Aboriginals and Anglo-Celts, and to determine whether higher all-cause mortality in Aboriginals is explained by a higher CKD prevalence.
Patients and Methods: The longitudinal Fremantle Diabetes Study Phase II includes 105 Aboriginal and 787 Anglo-Celt subjects with T2DM recruited between 2008 and 2011. This cohort was followed to death/census at end-March 2014.
Results: At baseline, the 892 patients had a mean±SD age of 65.7±11.5 years, 49% were male, and their median [inter-quartile range] diabetes duration was 8.0 [2.3-15.0] years. A higher proportion of Aboriginals had treated end-stage CKD (5.7% vs 0.4%, P<0.001), macroalbuminuria (25.8% vs 5.0%, P<0.001), and eGFR<30 ml/min/1.73m2 (8.7% vs 3.6%, P=0.031), with 19.6% of Aboriginals defined as being in the composite very high risk CKD category compared with 9.6% of Anglo-Celts (P=0.005). During a mean follow up of 4.3±1.2 years, 82 patients (10.8%) died. Excluding variables associated with renal impairment, Cox proportional hazards modelling with age as the time-line showed that all-cause mortality was predicted by male sex and current smoking, whilst being married/in a de facto relationship was protective. After adjusting for this most parsimonious model and adding eGFR categories with 45-59 ml/min/1.73m2 as reference, ≥90, 30-44, 15-29, and <15 ml/min/1.73m2 independently predicted higher mortality risk (hazard ratios (HRs) 10.4, 2.7, 3.0 and 21.1, respectively). After adjusting for this combined model, Aboriginals were 4.5 times more likely to die than Anglo-Celts (HR (95% CI: 4.50 (2.17-9.35)).
Conclusions: The relationship between eGFR and all-cause mortality is J-shaped in T2DM with the lowest mortality at 45-59 ml/min/1.73m2. Aboriginals have substantially increased mortality independent of CKD.