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Controlling Hypertension Doesn't Help Kidney Function

But study finds it can save lives anyway

TUESDAY, Nov. 19, 2002 (HealthDayNews) -- Stringent efforts to lower blood pressure in people with kidney disease don't prevent the loss of kidney function, but they do appear to save lives, a new study finds.

And one kind of pressure-lowering medication, an angiotensin-converting enzyme (ACE) inhibitor, clearly performed best in the patients with end-stage kidney disease caused by high blood pressure, says a report in tomorrow's Journal of the American Medical Association.

The report is the latest in a series on the African American Study of Kidney Disease and Hypertension (AASK). The 1,094 patients in the study are all black, an ethnic group especially prone to hypertensive kidney disease. Dr. Jason T. Wright Jr. and his colleagues at Case Western Reserve University undertook the study to see whether lowering blood pressure beyond a normal target level would prevent the loss of the kidneys' ability to filter impurities out of the blood. The study started in 1995, with some patients followed for as long as 6.4 years.

The loss of kidney function was no different in the patients in whom blood pressure was reduced to 128 over 78 as compared to those whose pressure was reduced to 141 over 85, the researchers report. "Our results do not support additional reduction as a strategy to prevent" loss of kidney function, they write.

The study concentrated on kidney function because some previous trials indicated that more strenuous control of blood pressure is needed to prevent loss of kidney function, says Wright, a professor of medicine at Case Western.

"Once patients are controlled to levels that prevent cardiovascular disease, then further reduction to prevent kidney disease progression is not necessary," says Wright.

However, Dr. Michael A. Alderman, a professor of medicine and epidemiology at the Albert Einstein College of Medicine, who wrote an accompanying editorial, says the extra reduction in blood pressure appears to be worth it if the patients' overall health, rather than just their kidney function, is considered.

"Most patients like this die of heart attacks and stroke, and in fact the patients with lower blood pressure did have fewer cardiovascular events," Alderman says. Data in the published report show that "cardiovascular mortality and hospitalizations were 16 percent more likely among those assigned to the higher, rather than lower, blood pressure goal," he says.

The study also tested the effects of an ACE inhibitor, ramipril (marketed as Altace), against two other drugs for high blood pressure, the beta blocker metopropolol (marketed as Lopressor) and the calcium channel blocker amlodipine (marketed as Norvasc). Ramipril came out ahead, with patients assigned to that drug having a 22 percent risk reduction compared to those taking metopropolol and a 38 percent risk reduction compared to those taking amlodipine.

"Our results do support the recommendations that ACE inhibitors should be considered as first-line therapy over beta blockers and calcium channel blockers in these patients," the researchers say.

That finding is "no surprise," Alderman says, because it has been made in previous studies involving white patients. The new study does strike at the belief held by some that hypertensive kidney disease in blacks is somehow different from the same disease in whites, he says. "The concern that there is a biological difference between blacks and whites is not right," Alderman says.

What To Do

You can learn more about hypertensive kidney disease from the National Institute of Diabetes and Digestive and Kidney Diseases. For information on kidney disease in general, try the National Kidney Foundation.

SOURCES: Jason T. Wright Jr., M.D., professor of medicine, Case Western Reserve University, Cleveland; Michael A. Alderman, M.D., professor, medicine and epidemiology, Albert Einstein College of Medicine, Bronx, N.Y.; Nov. 20, 2002, Journal of the American Medical Association
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