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 n ot wholly explained by the differences in the prevalence of diabetes. There fore, 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 attend ees of the diabetes clinic. Forty-five patients were found with renal impai rment (serum creatinine greater than or equal to 170 mu mol/l) due to diabe tic nephropathy. The patients were of Indo-Asian (n = 10), African-Caribbea n (n = 11), and Caucasian (n = 24) origin. Progression of nephropathy was a ssessed by analysing (i) the doubling of serum creatinine through construct ion of Kaplan-Meier curves and (ii) the slope (beta) of the rate of change in serum creatinine using linear regression analysis in relation to demogra phic variables, putative risk factors for nephropathy and antihypertensive drug therapy. Results. There were Ilo statistically significant differences between systo lic and diastolic blood pressure, glycaemic control, smoking habit, baselin e proteinuria. and usage of angiotensin-converting enzyme inhibitors betwee n the three groups. The proportion of patients doubling their creatinine wa s significantly higher in the Indo-Asian compared with the African-Caribbea n and Caucasian groups (100, 45 and 50%; P = 0.025 respectively). In additi on, the mean (95% CI) of beta (mu mol/l/month) was highest in the Indo-Asia n (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 bet a were highest in the Indo-Asian group (P = 0.038) after adjusting for marg inal 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 establis hed renal disease, the rate of decline in renal function is accelerated in Indo-Asian subjects. This observation could be related to differences in re noprotection from antihypertensive therapy.