Cholesterol Linked to Kidney Disease.

Researchers at the Johns Hopkins School of Public Health have found that high levels of triglycerides and low levels of high-density (good) cholesterol in the blood predict the onset of chronic kidney disease. By contrast, total cholesterol and low-density lipoprotein (LDL) cholesterol, which are important determinants of heart disease risk, did not predict kidney disease risk. Individuals who went on to experience an onset of chronic kidney disease also were substantially more likely to be older, black, diabetic, and hypertensive at the start of the study Findings from the study were reported in the June 2000 issue of Kidney International.

Five to 10 million Americans are estimated to be in the early stages of chronic kidney disease, having lost at least half their normal kidney function. Senior author Josef Coresh, M.D., Ph.D., noted, "Chronic kidney disease is only beginning to be recognized as a major public health problem. Our goal is to systematically understand why some individuals' kidney function declines more rapidly and why these individuals are at an increased risk of kidney failure and death. Heart and kidney disease share many risk factors. Understanding the similarities and differences will help us understand why treated kidney disease incidence is increasing while heart disease is decreasing."

The report focused on the risk of declining kidney function over three years following a baseline examination. A total of 15,792 men and women 45 to 64 years of age were followed at three-year intervals from 1987, as participants in the Atherosclerosis Risk in Communities Study. At the baseline examination, participants answered questions about kidney disease risk factors and gave blood samples, which were tested for the following lipid levels: total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, apolipoproteins A and B, and triglycerides.

Creatinine, a breakdown product of muscle, was used to detect chronic kidney disease. Since a rising level in creatinine in the bloodstream indicates a decline in the kidney's capacity to filter blood, the investigators defined an increase of 0.4 milligrams of creatinine per deciliter of blood as indication of a significant decline in kidney function.

The data revealed that higher triglyceride levels were consistently associated with a greater risk of increased creatinine levels and thus with a decrease in kidney function. Similarly, lower levels of HDL, or "good," cholesterol and of apolipoprotein-A (the major protein in HDL cholesterol) were associated with greater risk. By contrast, total cholesterol and LDL cholesterol showed no association with the risk of chronic kidney disease.

For each threefold increase in triglyceride levels, the risk of a rise in creatinine was 2.39 times greater among African-Americans and 1.31 times greater among whites. The associations remained when the study was limited to individuals with normal kidney function at baseline.

Lead author Paul Muntner said, "Among the lipids we investigated, triglycerides had the strongest and most statistically significant association with a future decline in renal function. Individuals with high triglycerides were one and a half times more likely to experience a decline in kidney function compared with individuals with low triglycerides." These associations persisted even after researchers took into consideration such variables as sex, race, age, diabetes status, systolic blood pressure, diabetes status, and type of blood pressure medication used.