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Anemia and other conditions related to chronic kidney disease are independently associated with the risk of cardiovascular disease; conversely, heart disease is associated with a decline in kidney function and the development of kidney disease, according to two reports in Archives of Internal Medicine, one of the JAMA/Archives journals.

Chronic kidney disease is becoming increasingly prevalent in the United States and worldwide, according to background information in the articles. Chronic kidney disease is associated with a wide variety of complications, including anemia (low red blood cell count, or red blood cells that are deficient in oxygen-transporting hemoglobin), nerve pain, bone disease, death and cardiovascular disease. Most patients with chronic kidney disease die of complications from heart disease rather than of kidney failure.

In one study, Peter A. McCullough, M.D., M.P.H., of William Beaumont Hospital, Royal Oak, Mich., and colleagues assessed a group of 37,153 individuals who were screened for kidney disease through a community-based program between 2000 and 2003. The participants (average age of 52.9 years) all reported a personal or family history of diabetes, hypertension or kidney disease on a screening survey. Patients had their blood pressure measured and provided blood and urine samples, which were processed to assess three markers of chronic kidney disease:

* estimated glomerular filtration rates (eGFR), or the rate at which kidneys filter blood, calculated based on levels of the waste product creatinine in the blood

* anemia, determined by blood hemoglobin levels

* and microalbuminuria, or slightly high levels (20 milligrams per liter or more) of the protein albumin in the urine

Of the participants who were followed for a maximum of 47.5 months, 5,504 (14.8 percent) had eGFR values of less than 60 milliliters per minute per 1.73 square meters, which were considered abnormal and signs of declining kidney function. In addition, 4,588 (13.1 percent) had anemia; and 15,959 (49.5 percent) had microalbuminuria. A total of 1,835 (4.9 percent) had a history of heart attack, 1,336 (3.6 percent) had a history of stroke and 2,897 (7.8 percent) had a self-reported history of heart attack or stroke.

Each of the three variables - anemia, microalbuminuria and low eGFR - was associated with cardiovascular disease. More than one-fourth of the patients who had all three kidney disease measures had cardiovascular disease, and their survival rates over the course of the study were lower by approximately 93 percent than those of any other group.

"These data suggest that screening for cardiovascular disease would be of high yield among patients with these risk markers but who do not report any history of cardiovascular disease symptoms," the authors conclude.

In a related study, Essam F. Elsayed, M.D., of Tufts - New England Medical Center, Boston, and colleagues evaluated a total of 13,826 individuals (average age 57.6) who had participated in one of two large cardiovascular health studies. Participants were recruited to the studies between 1987 and 1990 and followed up at approximately three-year intervals for an average of 9.3 years. At the beginning of the study and at each subsequent visit, blood creatinine levels were measured and used to track the decline in kidney function and the development of kidney disease both directly and by calculating eGFR. History of cardiovascular disease, as well as medication use, lifestyle characteristics, and other variables also were collected at the initial assessment.

At the beginning of the studies, 1,787 (12.9 percent) of the participants had cardiovascular disease. As measured by creatinine levels, 520 individuals (3.8 percent) experienced a decline in kidney function - including 128 (7.2 percent) of those with cardiovascular disease and 392 (3.3 percent) of those without cardiovascular disease - and 314 (2.3 percent) developed kidney disease. The presence of cardiovascular disease at the beginning of the study was associated with a decline in kidney function and the development of kidney disease as measured by both creatinine levels and eGFR.

"Our study demonstrates that cardiovascular disease is associated with subsequent kidney function decline and development of kidney disease," the authors conclude. "This study identifies a population that may benefit from (1) increased cardiovascular disease risk factor surveillance and intervention, (2) heightened awareness of the risk factors associated with kidney disease, and (3) greater attention to and treatment for sequelae of kidney disease."

"Because these patients are mainly under the care of primary care physicians and cardiologists, it is important to draw attention to the increased risk of kidney disease in this population, with goals of preventing further progression, managing sequelae of kidney disease as they arise and adequately preparing individuals for kidney failure with timely nephrology referrals. Only with recognition of risk factors for kidney disease can this happen."

(Arch Intern Med. 2007;167:1122-1129, 1130-1136)

Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Editorial: Focused Approach Will Reduce Heart and Kidney Disease Rates

The presence of cardiovascular disease should now be recognized as a risk factor for the development of kidney disease, and patients with both should be screened and treated accordingly, write Barry I. Freedman, M.D., and Thomas D. DuBose Jr., M.D., of the Wake Forest University School of Medicine, Winston-Salem, N.C., in an accompanying editorial.

These two reports "address the interactive effects of kidney disease and cardiovascular disease risk in more than 50,000 subjects," they write. "These studies provide novel insights into the relationship between kidney disease and the vasculature."

"The chances for reducing the current high rates of chronic kidney disease and cardiovascular disease will be maximized when primary care physicians, nephrologists and cardiologists work in partnership to reduce and treat modifiable vascular disease risk factors, including those that are a consequence of kidney disease," Drs. Freedman and DuBose conclude. "In addition, the potential for achieving current treatment goals in individuals at risk for nephropathy and cardiovascular disease using a more focused approach promises greater reductions in future cardiovascular disease and end-stage renal disease events."

(Arch Intern Med. 2007;167:1113-1115)

Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Article adapted by Medical News Today from original press release.

Contact: Ilene Wolff
JAMA and Archives Journals