December 2006: For African-Americans with high blood pressure, the combination of risk factors known as metabolic syndrome brings an increased risk of worsening kidney disease, reports a paper presented at the American Society of Nephrology's 39th Annual Meeting and Scientific Exposition in San Diego.
"Our study shows a 38 percent increased risk of progressive chronic kidney disease in hypertensive African-Americans classified as having the metabolic syndrome," comments Dr. J. P. Lea of Emory University, lead author of the new study. "This has important public health implications, as treatments are available to reduce the severity of the metabolic syndrome and may have an impact on reducing the rate of progressive kidney disease."
Dr. Lea and her fellow researchers analyzed data from a large study of treatment for hypertension (high blood pressure) in African-Americans. Twenty-five percent of the patients had metabolic syndrome, meeting at least three of the five diagnostic criteria: high blood sugar, low high-density lipoprotein ("good") cholesterol, high triglycerides, and obesity, and high blood pressure. (All patients automatically had one of the criteria, because all were hypertensive.)
Sometimes called insulin resistance syndrome or "syndrome X," metabolic syndrome is a known risk factor for diabetes, cardiovascular disease, and chronic kidney disease (CKD). Patients with CKD have gradual, irreversible loss of kidney function. Over time, CKD can lead to end-stage renal disease (ESRD)�permanent loss of kidney function requiring dialysis or kidney transplantation.
After four years' follow-up, the patients with metabolic syndrome had significantly higher rates of progressive CKD, defined as continued declines in kidney function, ESRD, or death. The risk of progressive CKD was about 40 percent higher for patients with metabolic syndrome, even after adjustment for other factors known to affect kidney disease outcomes�such as age, sex, obesity, and initial level of kidney function.
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On their own, none of the individual metabolic syndrome risk factors was related to progressive CKD. The increased risk associated with metabolic syndrome was also unaffected by which blood pressure treatment the patients received.
Although previous studies have linked metabolic syndrome to an increased risk of CKD, it has been unclear whether metabolic syndrome contributes to progression of established CKD. Once CKD is present, African-Americans have higher rates of progression to ESRD.
"Diabetes and hypertension are the leading causes of kidney failure, which disproportionately affects African-Americans," says Dr. Lea. "Despite good treatments for diabetes and hypertension, there is still a continued rise in the rates of kidney disease. More studies are needed to determine why some patients with CKD progress more rapidly to ESRD�that is, to dialysis�than others."
This study of African-Americans with high blood pressure finds that metabolic syndrome is a significant risk factor for progressive CKD. "Metabolic syndrome can contribute to worsening kidney disease," adds Dr. Lea. "That's important, because if we can reduce the severity of metabolic syndrome through diet and medication, it may help to reduce the rate of progressive kidney disease�and thus delay ESRD and the need for dialysis therapy, which is very costly and debilitating."
Source: American Society of Nephrology (ASN) / Newswise
