Renal disease patterns in aboriginal Australians. A family-based study in a high incidence community

Abstract

Objectives: To explore the apparent excess of renal disease in a coastal Aboriginal community in the Northern Territory and to explore its familial basis.

Design: Families were ascertained through probands with significant proteinuria. Controls were selected from unrelated subjects living with these families.

Participants: All surviving grandparents, parents, siblings, children and grandchildren of 16 probands were studied; there were 219 participants in all, including 58 adult control subjects.

Main outcome measures: Anthropometric data included the body mass index (BMI), and resting blood pressure. Urinary protein and creatinine levels were measured and urine was examined microscopically for glomerular haematuria (more than 10 red blood cells per microL, with at least 20% dysmorphic red cells). Two hours after a 75 g glucose drink, venous blood was taken and analysed for biochemical markers including urea, creatinine, glucose and gamma-glutamyltransferase.

Results: Significant proteinuria (protein to creatinine ratio greater than 50 mg/mmol), provided evidence of renal disease in 30% of both case relatives and control subjects. The prevalence of proteinuria was associated with increasing age, increasing diastolic blood pressure, increasing glucose level and female sex. However, two contrasting groups of subjects were identified in that relatives of probands had more glomerular haematuria than controls (27/112 v. 3/58, P = 0.005) and this was most marked in a family with multiple probands and in the parents of probands; in contrast, controls were more likely to have hypertension and obesity. Diabetes was highly prevalent in adult study subjects (12.4%) with no difference between controls and relatives of probands.

Conclusions: The very high prevalence of renal disease in Australian Aborigines parallels the situation in American Indian communities undergoing rapid cultural change. In the island Aboriginal community studied, proteinuria and glomerular haematuria are familial, possibly due to genetically influenced glomerulonephritis evoked by (unknown) environmental factors. Proteinuria associated with obesity, hypertension and diabetes is less obviously familial, and plausibly related to poor nutrition and other lifestyle factors. The high prevalence of proteinuria and other risk factors in community-based studies and the high incidence of end-stage renal disease show that there is an urgent need for effective education and prevention programs, for more active treatment of hypertension, and for further work to clarify the aetiology and pathogenesis of renal disease in Aboriginal communities.