Reducing African American patientsí blood pressure often proves difficult, but doing so can dramatically slow kidney disease, says clinical researcher George Bakris.
By Lydialyle Gibson
Photograph by Dan Dry
In 1991 officials from the National Institutes of Health (NIH) convened a study group of physicians from across the country to give advice about renal-disease progression in African Americans. Previous research had shown hypertension to be a leading cause of chronic kidney failure, and blacks were six times more likely than whites to develop kidney disease from high blood pressure. For patients 25 to 44 years old, the racial disparity was particularly striking; blacks faced a risk that was twentyfold higher. Meanwhile, although African Americans made up 12 percent of the U.S. population, they accounted for a third of patients treated for kidney failure.
“So the question was, why?” says Chicago clinical researcher George Bakris, AM’75, one of those invited to take part in the NIH group. Bakris, who completed Chicago fellowships in clinical pharmacology and nephrology in the late 1980s, researches how kidney disease, diabetes, and high blood pressure develop and progress, and what therapies work best against them (in 2007 he made a few headlines with a study suggesting a chiropractic neck adjustment might lower blood pressure). Helping to conduct dozens of clinical trials—right now he has about ten under way or upcoming—Bakris often concentrates on ethnic disparities in illnesses. Since 2006 he has directed the U of C’s hypertension center and taught clinical-research methodology in the Pritzker School of Medicine. In 1991, when the NIH came calling, he was an assistant professor at the University of Texas Health Science Center at San Antonio.
“The NIH wanted to know what was going on” with African American kidney disease, he says. “But there were very few answers at the time.” Not many African Americans had been included in clinical trials showing that lowered blood pressure could slow the progress of renal disease and that for people whose kidney failure stemmed from diabetes, a class of drugs called angiotensin-converting enzyme (ACE) inhibitors could help significantly. Meanwhile, the decade between 1980 and 1990 saw an uptick in end-stage renal disease, especially among African Americans. The NIH decided to launch a study.
What became known as the AASK trial—the African American Study of Kidney Disease and Hypertension, the largest of its kind—recruited 1,094 patients between 18 and 70 years old, all black and all suffering mild hypertensive kidney disease. One of AASK’s principal investigators, Bakris says the five-year study sought to answer two main questions: does long-term blood-pressure control help to slow African Americans’ renal disease, and does one hypertension drug protect the kidneys more than another?
By 2002 Bakris and his colleagues had answers, and among them were some surprises. First, ACE inhibitors, “long thought to be ineffective in blacks,” Bakris says, proved quite effective, much more so than calcium channel blockers (CCBs) or beta blockers—two other types of commonly used hypertension drugs—at lowering blood pressure and protecting the kidneys. “Big finding,” he says. “And ACE inhibitors are better tolerated in blacks than had been thought.”
But the AASK trial, along with a follow-up study with 750 of the original patients, also showed that although “aggressive blood-pressure management” slowed kidney disease, Bakris says, it rarely stopped it. This past April he and his AASK colleagues reported in the Archives of Internal Medicine that two-thirds of patients’ renal disease continued to advance, despite drug therapy and good blood-pressure control. “And lots of these people’s blood pressure didn’t drop when they slept,” he says. “That’s a big deal.” Others had “masked hypertension”: “In the doctor’s office your blood pressure’s fine,” Bakris explains, “but you go outside and it elevates. Could be genetic, or could be environmental—maybe you have a stressful job, maybe you live in a neighborhood where people are getting shot.” These are perplexities Bakris and his colleagues are still working to understand.
In the meantime, Bakris has been analyzing the remarkable results of another trial, called accomplish. Examining the risk of stroke, heart attack, or other cardiovascular crisis for diabetics with advanced kidney disease, the study compared a drug regimen pairing ACE inhibitors and CCBs with another pairing ACE inhibitors and diuretics. The trial was halted a year early with indisputable results: the CCB combo reduced relative cardiovascular risk by 20 percent, “which flies in the face of guidelines that say everybody and their mother should be on diuretics,” Bakris says. “We’re all blown away.” Up next: studies involving children with pre-hypertension, cholesterol levels in patients over 75, and “vascular compliance” in diabetics with renal disease. Says Bakris: “It never stops.”