Hypertension, glomerular hypertrophy and nephrosclerosis: the effect of race

BACKGROUND: African Americans have more severe hypertensive nephrosclerosis than white Americans, possibly at similar levels of blood pressure. Glomerular volume is increased in African Americans relative to whites, but it is uncertain how this relates to nephrosclerosis and whether it contributes to or compensates for glomerulosclerosis. METHODS: Stereological disector/fractionator estimates of glomerular number (N(glom)) and average glomerular volume (V(glom)) were obtained on autopsy kidneys of 171 African Americans and 131 whites. Eighty-eight African Americans and 49 whites were identified as hypertensive. Nephrosclerosis was measured morphometrically as the percentage of glomerulosclerosis, proportion of cortical fibrosis and interlobular artery intimal thickness, and analyzed with V(glom) by age, race, gender, body mass index (BMI) and blood pressure. RESULTS: African Americans were more frequently hypertensive (58.5%) than whites (35.8%) and when hypertensive had higher levels of blood pressure (P = 0.02). N(glom) was significantly lower in hypertensive compared with non-hypertensive subjects among white women (P = 0.02) but not white males (P = 0.34) or African American females (P = 0.10) or males (P = 0.41). For each race and gender, glomerulosclerosis, cortical fibrosis and arterial intimal thickening were statistically correlated with age (P < 0.001) and hypertension (P < 0.001) and increased V(glom) with hypertension (P < 0.001) and BMI (P < 0.001). In multivariate analysis, African American race was associated with increased V(glom) (P = 0.01) and arterial intimal thickening (P < 0.01), while interactions between race and blood pressure indicated that the severity of nephrosclerosis including increased V(glom) was linked most directly to hypertension without significant contributions from race. The hypertension-associated enlargement of V(glom) was present with mild degrees of glomerulosclerosis and changed little as the severity of glomerulosclerosis increased. CONCLUSIONS: Glomerular hypertrophy was identified as an integral feature of hypertensive nephropathy and appeared to precede rather than compensate for glomerulosclerosis. An effect of race on V(glom) and arterial intimal thickening seemed to be related to the more frequent and more severe hypertension among African Americans.