African-Caribbean ethnicity is an independent predictor of significant decline in kidney function in people with type 1 diabetes

  

Objective: The aim of the study was to identify the demographic and clinical features in an urban cohort of people with type 1 diabetes who developed ≥50% decline in estimated glomerular filtration rate (eGFR). 

Research design and methods: We evaluated 5261 people with type 1 diabetes (51% female, 13.4% African-Caribbean) with baseline eGFR >45ml/min/1.73m2. Primary endpoint was an eGFR decline ≥50% from baseline with a final eGFR <30ml/min/1.73m2. eGFR was calculated by Chronic Kidney Disease Epidemiology Collaboration equation. 

Results: Of the cohort 263 (5%) reached the primary endpoint. People who reached primary endpoint were more likely to be of African-Caribbean ethnicity, older, with a longer duration of diabetes, higher systolic blood pressure and HbA1c, more prevalent retinopathy, and higher albuminuria categories (p<0.05 for all). In multivariable Cox regression models, African-Caribbean ethnicity emerged as a significant risk factor for the primary end-point with a hazard ratio 1.57 (95% confidence interval 1.19-2.08) compared to other ethnicities, independent of established risk factors (p<0.01). The incident rate for the primary endpoint in African-Caribbean people was double that in non African Caribbean people (16 per 1000 patient years versus 7.7 per 1000 patient years, p<0.001). A similar significant independent impact of African-Caribbean ethnicity for secondary endpoints (≥40% or ≥30% fall in eGFR) was observed. 

Conclusion: We report a novel observation that African-Caribbean ethnicity increased the risk of kidney function loss, an effect which was independent of traditional risk factors. Further studies are needed to examine the associated pathophysiology that may explain this observation.