THURSDAY, June 14, 2007 (HealthDay News) -- Ailing kidneys can harm the heart and vice-versa, according to two studies highlighting the close connection between the two systems.
The studies, published in this week's issue of the Archives of Internal Medicine, concluded that anemia and other conditions related to chronic kidney disease are associated with an increased risk of cardiovascular disease, and that heart disease is associated with a decline in kidney function and the development of kidney disease.
The first study, by researchers at William Beaumont Hospital, in Royal Oak, Mich., followed more than 37,000 people (averaging about 53 years of age) for almost 48 months. On a screening survey at the start of the study, all the participants reported a personal or family history of diabetes, hypertension or kidney disease.
Blood and urine samples were collected from the volunteers to assess three markers of kidney disease:
- estimated glomerular filtration rate (eGFR) -- the rate at which kidneys filter blood;
- microalbuminuria -- elevated levels of the protein albumin in the urine.
The study found that almost 15 percent of the participants had eGFR rates that indicated declining kidney function, about 13 percent had anemia, 49.5 percent had microalbuminuria, and almost 8 percent had a self-reported history of heart attack or stroke.
Each of the three markers of kidney disease was also associated with cardiovascular disease, the study author said. More than 25 percent of participants who had all three kidney disease markers had cardiovascular disease, and they had a 93 percent lower survival rate over the course of the study than other participants.
"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 study authors wrote.
The second study, by researchers at Tufts-New England Medical Center in Boston, looked at data from more than 13,800 people (average age 57.6 years) who took part in two large cardiovascular health studies that began in 1987 and 1990. The participants were followed for an average of just over nine years.
The researchers found that 7.2 percent of those who had cardiovascular disease at the start of the studies experienced a decline in kidney function during the research period, compared with 3.3 percent of those who did not have cardiovascular disease.
"Our study demonstrates that cardiovascular disease is associated with subsequent kidney function decline and development of kidney disease," the study authors wrote.
"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," they added. "Only with recognition of risk factors for kidney disease can this happen."
The U.S. National Kidney Disease Education Program has more about kidney disease.