Association between race and incidence of end-stage renal disease secondary to glomerulonephritis: influence of the histologic type and presence of arterial hypertension

Abstract

To assess, retrospectively, the association between race and incidence of end-stage renal disease (ESRD) in patients with glomerulonephritis in a University Hospital of Bahia, Brazil. The sample was comprised of 79 patients with focal segmental glomerulosclerosis (FSG), 50 with membranoproliferative glomerulonephritis (MPGN) and 49 with other types of glomerulonephritis (OTGN), followed-up between 1970 and 1996 for at least 6 months. It was not included patients with acute glomerulonephritis, minimal change disease, crescentic glomerulonephritis, connective tissue diseases or patients with serum creatinine level greater than or equal to 4.0 mg/dl. The patients were classified according to race as caucasian (white), mulatto or negro. For patients older than 18 yr, not taking antihypertensives drugs, hypertension was defined as a mean of three blood pressure measurements greater than or equal to 140 mmHg for systolic or 90 mmHg for diastolic; for ages </= 18 years. The definition was based on criteria recommended by the Task Force on Blood Pressure in Children. In the normotensive group, the incidence of ESRD was 72% lower in mulattos and negroes (relative risk (RR)=0.28; 95% confidence interval (CI)=0.11-0.67). In the group with hypertension, the direction of association between race and ESRD was opposite to that observed in the normotensive group (RR=1.49; 95% CI= 0.68-4.34). The modification in the RR depending on the presence or the absence of hypertension was statistically significant (p=0.01). In the normotensive group the RR shifted toward the null hypothesis after the inclusion of histologic type in the Cox model. Among normotensive patients with glomerulonephritis the incidence of ESRD was greater in caucasians (whites) than in negroes or mulattoes. By contrast among hypertensive patients there was a trend for a higher risk of ESRD in negroes. The study suggests that hypertension and the histologic type of glomerulonephritis influence the association between race and ESRD.