Variation in the progression of diabetic nephropathy according to racial origin

BACKGROUND: In the United Kingdom, diabetic nephropathy is a leading cause of end-stage renal disease. There is a higher incidence amongst subjects of Indo-Asian and African-Caribbean origin compared with Caucasians that is not wholly explained by the differences in the prevalence of diabetes. Therefore, we postulated that this observation could be related to variations in the rate of progression of renal disease according to racial origin. METHODS: We conducted a retrospective case-note review of 1684 adult attendees of the diabetes clinic. Forty-five patients were found with renal impairment (serum creatinine > or = 170 micromol/l) due to diabetic nephropathy. The patients were of Indo-Asian (n=10), African-Caribbean (n=11), and Caucasian (n=24) origin. Progression of nephropathy was assessed by analysing (i) the doubling of serum creatinine through construction of Kaplan-Meier curves and (ii) the slope (beta) of the rate of change in serum creatinine using linear regression analysis in relation to demographic variables, putative risk factors for nephropathy and antihypertensive drug therapy. RESULTS: There were no statistically significant differences between systolic and diastolic blood pressure, glycaemic control, smoking habit, baseline proteinuria, and usage of angiotensin-converting enzyme inhibitors between the three groups. The proportion of patients doubling their creatinine was significantly higher in the Indo-Asian compared with the African-Caribbean and Caucasian groups (100, 45 and 50%; P=0.025 respectively). In addition, the mean (95% CI) of beta (micromol/l/month) was highest in the Indo-Asian (5.36 (2.21-8.52)) compared with the African-Caribbean (3.14 (0.82-5.46)) and Caucasian (2.22 (1.31-3.14)) groups (P=0.035). The mean ranks of beta were highest in the Indo-Asian group (P=0.038) after adjusting for marginal differences in blood pressure age, gender, baseline proteinuria, anti-hypertensive treatment, and smoking habit. CONCLUSIONS: In this small cohort of type 2 diabetic subjects with established renal disease, the rate of decline in renal function is accelerated in Indo-Asian subjects. This observation could be related to differences in renoprotection from antihypertensive therapy.