Differences in biopsy-proven diabetic kidney disease in individuals from Polynesia vs mainland France: a retrospective cohort study.

Abstract

Aims/hypothesis: Māori, a Polynesian population, have an earlier age of onset of type 2 diabetes and higher risk of diabetes-related complications compared with New Zealanders of European descent, and an increased incident rate ratio for end stage kidney disease. No data are available regarding the evolutive characteristics of diabetic kidney disease (DKD) in individuals living in French Polynesia.

Methods: We aimed to compare the retrospectively collected characteristics and outcomes of 92 and 63 individuals from French Polynesia and mainland France, respectively, presenting type 2 diabetes and biopsy-confirmed DKD, focusing on kidney survival, analysis of the Renal Pathology Society (RPS) score and participant survival.

Results: At the time of biopsy, Polynesian participants were younger (56.5 vs 66.9 years, p<0.001) and had a higher urinary protein/creatinine ratio (uPCR) (792 vs 452 mg/mmol, p<0.001), despite similar anti-proteinuria treatments and eGFR, and shorter time since diabetes diagnosis (8.7 vs 11.1 years, p=0.008). Polynesian participants had a more severe RPS classification (p<0.001). Median time from biopsy to kidney failure with replacement therapy was 1.59 years in the Polynesian population and 6.06 years in the mainland French population, accounting for death as a competing risk. Polynesian participants were at a higher risk of end stage kidney disease after adjustment for uPCR, eGFR, BMI and age at baseline (HR 2.45 [95% CI 1.23, 4.88]). In a clinical and histological reduced multivariable model, Polynesian origin, higher uPCR, lower eGFR, more severe RPS classification and presence of chronic vascular lesions were all independently associated with poorer kidney survival. The RPS classification was more strongly associated with kidney survival in participants from Polynesia (p value for interaction, 0.048), while a higher uPCR was more strongly associated with kidney survival in participants from mainland France (p value for interaction, <0.001). Older age and Polynesian origin were also independent risk factors for death.

Conclusions/interpretation: Starting at an earlier age, the evolutive course of DKD is also more severe in individuals from French Polynesia than from mainland Western Europe. Strong differences in clinical, histological and predictive outcomes of diabetic nephropathy were found in these different ethnic groups.