Studies Strengthen Kidney and Heart Disease Link

A pair of new epidemiology studies confirms that chronic kidney disease independently increases the risk of developing cardiovascular disease, even among persons with early kidney disease and after considering other risk factors such as diabetes, hypertension and high cholesterol. The studies appear in the September 23 New England Journal of Medicine.

One of the studies, “Chronic Kidney Disease [CKD] and the Risk of Death, Cardiovascular Events, and Hospitalization,” was supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at NIH, part of the Department of Health and Human Services.

These studies “reinforce the importance of early detection of CKD, not only to slow progression to [kidney failure] but also in this case to identify risk factors for cardiovascular disease,”
said Thomas H. Hostetter, M.D., in an editorial accompanying the papers. Hostetter is a kidney specialist and director of the National Kidney Disease Education Program at NIDDK.

The NIDDK-funded study followed over 1.1 million adults from the Kaiser Permanente Renal Registry in San Francisco for nearly 3 years; average age was 52 years. Led by Alan S. Go, M.D., the investigators found that when kidney function (GFR) dropped, the risk of death, cardiovascular events such as heart disease and stroke, and hospitalization increased. Compared to patients whose GFR was at least 60 (ml per min. per 1.73 m2):

• The increased risk of death ranged from 17% in those whose GFR was between 45 and 59 to about 600% in those whose GFR was less than 15
• The increased risk of CVD events ranged from 43% in those whose GFR was between 45 and 59 to 343% in those whose GFR was less than 15, and
• The increased risk of hospitalization ranged from 14% in those whose GFR was between 45 and 59 to 315% in those whose GFR was less than 15.

The industry-funded VALIANT study related CKD to deaths from CVD in a 2-year drug-treatment trial of over 14,500 heart-attack patients. The researchers found death rates ranging from 14.1% in patients whose GFR was at least 75 to 45.5% in those whose GFR was less than 45. The investigators attribute the increased risk of death from CVD in part to complications of kidney disease, including anemia, oxidative stress, changes in calcium and phosphate regulation, inflammation, and conditions promoting clotting. The researchers also suggest that other kidney-related factors such as protein in the urine and elevated blood levels of both homocysteine and uric acid may increase the risk of CVD and death. Furthermore, they found that common CVD therapies such as aspirin and beta-blockers were “curiously underused” in CKD patients with lower kidney function, perhaps inspired by a fatalist mind-set that may be a self-fulfilling prophecy.

It is thought that 10 to 20 million people have CKD. While A lot of will never develop kidney failure, others will, joining over 400,000 people annually treated with dialysis or a kidney transplant. CVD accounts for half of all deaths among persons with kidney failure.