A Low Blood Pressure Target Prevented Kidney Failure in Patients with Chronic Kidney Disease

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The summary below is from the full report titled "The Effect of a Lower Target Blood Pressure on the Progression of Kidney Disease: Long-Term Follow-up of the Modification of Diet in Renal Disease Study." It is in the 1 March 2005 issue of Annals of Internal Medicine (volume 142, pages 342-351). The authors are M.J. Sarnak, T. Greene, X. Wang, G. Beck, J.W. Kusek, A.J. Collins, and A.S. Levey.

What is the problem and what is known about it so far?

Chronic kidney disease is a gradual and progressive loss of function in both kidneys. Many patients with chronic kidney disease have high blood pressure. Doctors usually use drugs to reduce blood pressure and decrease risks for heart attacks, strokes, and kidney failure. Most experts recommend reducing blood pressure to less than 140/90 mm Hg in adults with high blood pressure. In adults with certain conditions, such as diabetes or chronic kidney disease, experts often recommend reducing blood pressure to less than 130/80 mm Hg. No long-term clinical trials have tested whether reducing blood pressure to the lower levels prevents kidney failure in patients with chronic kidney disease.

Why did the researchers do this particular study?

To see whether a low blood pressure target prevents kidney failure in patients with chronic kidney disease.

Who was studied?

840 middle-aged adults with mild to moderate chronic kidney disease from causes other than diabetes. The average blood pressure at study entry was about 130/80 mm Hg because many patients were already taking drugs that reduced blood pressure.

How was the study done?

The researchers used a national database (the U.S. Renal Data System) to see whether patients who had participated in a trial from 1989 to 1993 later developed kidney failure until 2000. In the initial trial, researchers randomly assigned patients to either a low blood pressure target (less than 125/75 mm Hg) or a usual blood pressure target (less than 140/90 mm Hg). They measured patients' blood pressures monthly and adjusted treatment as needed to help patients meet the target blood pressure goals. During the initial trial period, they achieved average blood pressure levels of about 126/77 mm Hg in the low target group and 134/81 mm Hg in the usual target group. Then, the researchers compared numbers of people in each group who later developed kidney failure until 2000. Kidney failure was defined as the need for dialysis or a kidney transplant.

What did the researchers find?

Fewer patients (62%) in the low blood pressure target group developed kidney failure than did those (70%) in the usual blood pressure group.

What were the limitations of the study?

The researchers did not track patients' blood pressures after the original trial ended in 1993. We do not know whether patients assigned to the low blood pressure target group maintained their relatively low blood pressures over time.

What are the implications of the study?

Targeting a low blood pressure goal of less than 130/80 mm Hg may prevent kidney failure in some adults with mild to moderate chronic kidney disease.