Ethnicity and renal disease: lessons from the Multiple Risk Factor Intervention Trial and the Treatment of Mild Hypertension Study.

Hypertension, particularly severe hypertension, has proven to be a risk factor for renal disease. Whether the relationship of blood pressure (BP) and high renal disease exists across a wide range of BP levels has been less clear. Compared with whites, blacks have a higher rate of end-stage renal disease from a multiplicity of causes, including hypertension, most prominently in younger age groups. To examine ethnic patterns of renal disease across BPs spanning the range of "normal" to "elevated," data were summarized from three large studies: (1) 12-year mortality for the 347,978 men (22,471 black and 325,507 white) without prior myocardia infarction (MI) screened for the Multiple Risk Factor Intervention Trial (MRFIT) who have been followed an average of 12 years for cause-specific mortality, (2) the baseline and 6-year change in renal function in 5,524 hypertensive men (463 black and 5,061 white) randomized in the MRFIT, and (3) the baseline and 1-year change in creatinine level are compared in 902 black and white men and women (177 black and 725 white) with mild hypertension in the Treatment of Mild Hypertension Study (TOMHS). In the MRFIT screenees, there was a monotonic increase in the risk of renal mortality at higher BP levels, even within the "normal range," both in black and white men. Blacks had higher baseline creatinine levels in both the MRFIT and TOMHS. In the MRFIT hypertensive patients, 6-year change in creatinine predicts coronary heart disease and all-cause mortality while the baseline creatinine level did not. Comparisons of randomized groups in the MRFIT or TOMHS did not demonstrate improved renal function with more aggressive BP lowering, but in MRFIT average on-treatment DBP < 95 mm Hg was associated with more favorable slopes of reciprocal creatinine. At 1 year, no gender-specific ethnic differences in creatinine change were observed in TOMHS. In the MRFIT hypertensive men, 6-year creatinine change was slightly more favorable in white men than in black men (-0.088 mumol/l v +3.09 mumol/L, P = 0.004). These data demonstrate (1) a graded and continuous relationship between BP and renal disease in blacks and whites across a wide BP range, (2) that creatinine change predicts subsequent mortality, at least in hypertensive men treated with diuretic-based pharmacologic regimen, and (3) possibly different pattern of creatinine change in response to antihypertensive drug therapy in blacks and whites.