South-Asian type 2 diabetic patients have higher incidence and faster progression of renal disease compared with Dutch-European diabetic patients.

S urinamese South-Asian migrants, living in the Netherlands and aged 30 years, have a nearly 40-fold increased age-adjusted risk for end-stage diabetic nephropathy in comparison with their European Dutch counterparts (1). Several studies in the U.K. also showed a higher incidence of end-stage renal failure in South-Asian diabetic patients (2– 6). There is no clear explanation for the increased risk in South-Asian migrants, who originally descend from the Indian subcontinent. An earlier study showed no familial predisposition for renal disease in South-Asian migrants (7). There is a discrepancy between the reported eighttimes higher prevalence of diabetes (8) and the 40-fold higher risk of end-stage diabetic nephropathy (1) in this population. This discrepancy could be explained by either a higher incidence of nephropathy in the Asian diabetic patients and/or faster progression to end-stage renal failure. We performed a cohort study in South-Asian and Dutch-European type 2 diabetic patients to compare differences in the incidence of microalbuminuria and progression of renal failure between both ethnic groups. RESEARCH DESIGN AND METHODS — We used the registry of the outpatient diabetic clinic of the Haga Teaching Hospital during the period of 1994–1996. Ethnicity was by self-report. Migrants who originally descend from the Indian subcontinent were reported as South-Asian. Patients who were of Dutch descent were reported as European. We selected a cohort of 149 South Asian type 2 diabetic patients and matched them for sex and level of urinary albumin excretion with 155 European patients. Urinary albumin excretion and creatinine clearance were measured at inclusion and after 5 years’ follow-up. In each group, 7% of the patients were lost to follow-up and 11% had incomplete follow-up data for final analysis. Mortality was higher in the European patients: 19.3 vs. 6.7% in the South Asians. All laboratory measurements were done according to ISO 15189 standard procedures. Microalbuminuria was defined as albuminuria 30 mg in a 24-h urine collection or spot-urine albuminto-creatinine ratio 2.5 g/mol creatinine in male subjects and 3.5 g/mol creatinine in female subjects. Creatinine clearance was calculated from the 24-h urine per 1.73 m. For statistical comparison of the difference of means, the Student’s t test was used. Differences of categorical variables were expressed as a percentage with 95% CIs and as 2 P values. We used multivariate analysis for correction of differences in risk factors for development of microalbuminuria/macroalbuminuria. The decline in creatinine clearance ( glomerular filtration rate [GFR]) was calculated per patient.