Kidney Disease Research Updates
Lower Blood Pressure Goal Benefits African Americans with Chronic Kidney Disease and Protein in the Urine
On average, a lower blood pressure goal was no better than the standard blood pressure goal at slowing progression of kidney disease among African Americans who had chronic kidney disease (CKD) resulting from high blood pressure, according to results of the African-American Study of Kidney Disease and Hypertension (AASK).
The lower blood pressure goal, however, did benefit people who also had protein in the urine, a sign of kidney damage. In fact, among people with CKD and protein in their urine, keeping blood pressure at the lower level reduced the likelihood of kidney disease progression, kidney failure, or death by 27 percent compared with the standard blood pressure level, a statistically significant difference.
“For some patients, more intensive control of blood pressure may slow progression of chronic kidney disease,” said Griffin P. Rodgers, M.D., M.A.C.P., director of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). “Rigorous, long-term studies like the AASK remain critically important for improving treatment of CKD and other diseases that develop over time, as it can take years for benefits of treatment to emerge.”
The new information provided by the AASK may help doctors practice evidence-based, personalized medicine—the tailoring of treatment to patients’ unique characteristics. “The AASK study is the largest and longest study of kidney disease in African-Americans. It is a landmark study that is paying off—guiding patient care and improving health outcomes,” said Lawrence Appel, M.D., The Johns Hopkins University, who chaired the study.
In the United States, high blood pressure causes about a third of new kidney failure cases, also known as end-stage renal disease (ESRD). The cost to the Government and private payers for ESRD now exceeds $35 billion annually. The study results could help lower these costs by helping guide more effective treatments.
“For nearly two decades, the AASK research has provided valuable information about the most desirable, long-term chronic kidney disease treatment options for African-Americans, who bear a disproportionate burden of this debilitating disease,” said Lawrence Agodoa, M.D., director of the Office of Minority Health Research Coordination at the NIDDK. “People who participate in studies like AASK provide important information on how to protect the kidneys and preserve overall health.”
Clinical Trial and Follow-up
The study was conducted in two phases over 12 years, during which the AASK followed participants to measure the long-term effects of blood pressure control in African Americans with kidney disease attributed to high blood pressure.
Study participants were initially recruited beginning in 1995 for the AASK Clinical Trial, which lasted until 1998. Participants were randomly assigned to a standard blood pressure goal of roughly 140/90 millimeters of mercury (mmHg) or a lower goal of less than 130/80 mmHg. Patients with diabetes and some other serious health problems were excluded. After the conclusion of the clinical trial, AASK participants who had not yet developed ESRD were invited to participate in the AASK follow-up study beginning in 2002, in which everyone had a blood pressure goal of less than 130/80 mmHg.
In the follow-up study, recommended blood pressure therapy started with an angiotensin converting enzyme (ACE) inhibitor. This medication works by blocking the action of the protein angiotensin, which raises blood pressure. If blood pressure was not controlled, additional drugs were added. On average, patients needed about 3.5 medications for blood pressure each day. Millions of Americans take the drugs used in this study or drugs like them to treat health problems such as high blood pressure or heart disease.
“This study also highlights the importance of conducting long-term clinical studies,” Appel said. “Without the follow-up study, the benefits of the lower goal would have been missed.”
The AASK trial and the follow-up study were conducted at 22 U.S. medical centers and were funded by the NIDDK beginning in 1994. Additional support was provided by the National Institutes of Health’s National Institute on Minority Health and Health Disparities, King Pharmaceuticals, and other pharmaceutical companies that donated study drugs. The current report appeared in the September 2 issue of The New England Journal of Medicine.
For more information about the AASK, visit www.nih.gov/news/pr/nov2002/niddk-25.htm.
For a list of centers enrolling patients for kidney disease trials, search keywords “kidney disease” at www.ClinicalTrials.gov.
For an NIDDK publication about high blood pressure and kidney disease, visit www.kidney.niddk.nih.gov/kudiseases/pubs/highblood.
NIH Publication No. 11–4531