Aggressively lowering blood pressure does not prevent further kidney damage in African Americans unless they already have protein in their urine, a sign of more advanced kidney disease. In that case, aggressive treatment reduces end-stage kidney disease and death by about 25%, researchers said Wednesday. Data from the same study had earlier shown that the aggressive treatment does not prevent kidney-disease progression over a four-year period, but the new results reported in the New England Journal of Medicine extend the findings out to 12 years.
For reasons that are not totally clear, blacks are disproportionately affected by kidney disease, accounting for about a third of all end-stage kidney failure even though they represent only 12% of the population. About a third of all kidney disease in all races is caused by high blood pressure, and the cost to Americans is staggering. Treating chronic kidney disease costs about $49 billion per year, while an additional $23 billion is spent on dialysis and other care for those with kidney failure.
The African-American Study of Kidney Disease and Hypertension (AASK) began in 1995 to determine how much blood pressure had to be lowered to benefit patients. It enrolled 1,094 black men with high blood pressure and early evidence of kidney disease. About a third of them already had protein in their urine, a sign of more extensive kidney damage. The patients were randomly assigned to one of two groups. One group was targeted to get their blood pressure below 140/90 millimeters of mercury, a level generally considered borderline hypertensive but the standard target for physicians treating hypertension. The rest were targeted to get their blood pressure below 130/80 mm Hg through more intensive use of drugs. On average, the patients in the second group received 3.5 blood pressure drugs, while those in the first group averaged 2.5.
In the longer follow-up, a research team headed by Dr. Lawrence J. Appel of the Johns Hopkins University School of Medicine found that, for the two-thirds of patients with no protein in their urine at the start of the study, the two treatment regimens produced comparable results. But the more aggressive regimen produced a 25% reduction in end-stage kidney disease and death in those who had protein in their urine at the beginning.
"This has always been a hot topic: Is a lower blood pressure goal better at preserving kidney function than the standard goal?" Appel said in a statement. "The answer is a qualified yes, notably in people who have some protein in their urine."
Although the results were obtained in blacks, most researchers think they can be generalized to other races as well.
The bottom line, Appel noted, is that physicians should check urine protein concentrations before beginning intensive hypertension therapy. If the protein is not present, patients could then be spared the added cost, extra monitoring and additional side effects linked to the aggressive treatment.
-- Thomas H. Maugh II / Los Angeles Times