Tight BP Control Not Enough for Kidney Disease in African Americans

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Title: Tight BP Control Not Enough for Kidney Disease in African Americans
URL: http://www.pslgroup.com/dg/2204CA.htm
Doctor's Guide
April 28, 2008

BALTIMORE, Md -- April 28, 2008 -- Even when their blood pressure is kept under strict control, African American patients with chronic kidney disease (CKD) continue to lose kidney function over time. This finding, presented by a team from Johns Hopkins School of Medicine, Baltimore, Maryland, suggests that treating CKD in this population may be vastly more complex than researchers had previously thought, with blood pressure control being only one piece of the therapeutic puzzle.

The study, called African American Study of Kidney Disease and Hypertension (AASK), is the longest to date focusing on blood pressure in patients with CKD. AASK followed 1,094 African American patients with this condition for up to 11 years. Through a combination of medications, most of these patients kept their blood pressure in the recommended range for CKD, lower than 130/80 mm Hg. However, the vast majority still went on to develop steadily worsening kidney function, often leading to dialysis, kidney transplantation, or death.

″Kidney disease still progressed at an alarming rate, even when our participants received outstanding medical care for their high blood pressure,″ said study leader Lawrence Appel, MD, Professor of Medicine at the Johns Hopkins School of Medicine.

To investigate whether keeping blood pressure low would slow or possibly stop CKD progression, the researchers designed their study in 2 phases. In the first phase, the researchers randomly assigned all 1,094 patients to 1 of 3 drugs commonly used to lower blood pressure -- an angiotensin-converting enzyme (ACE) inhibitor, an alpha-blocker, or a calcium channel blocker. Each patient was also assigned to 1 of 2 blood pressure goals -- a standard goal (140/90 mm Hg or lower) or a more aggressive goal (130/80 mm Hg or lower). The researchers tracked all patients' blood pressure and kidney function, determined through blood and urine tests, as well as their overall health.

At the end of the first phase, the researchers found that about a third of the patients had lost at least half of their kidney function, had developed end-stage renal disease, or had died, even though almost all were well within their blood pressure goals. Of the remaining patients, the researchers recruited 759 to continue to the study's next phase. Early findings from the first phase showed that the ACE inhibitor worked better than the other treatments, so the remaining patients began taking that drug. They were also given the more aggressive blood pressure goal of 130/80 mm Hg.

Over the next 5 years, the researchers again tracked patients' blood pressure, kidney function, and overall health. However, even though these patients were receiving the new and improved treatment, a third still lost at least half of their kidney function, developed end-stage renal disease, or died.

These results, published in the April 28 Annals of Internal Medicine, should not discourage patients with CKD from continuing their blood pressure therapy, said Dr. Appel. ″Outcomes would certainly be worse if they didn't control their blood pressure.″ He added that the findings suggest that other factors beyond just blood pressure may be at play in worsening CKD. Blood pressure spikes at night, high salt intake, or exposure to heavy metals such as lead or mercury may influence kidney disease progression.

SOURCE: Johns Hopkins School of Medicine

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