Chronic Kidney Disease is Common in the U.S. and is Strongly Associated with Under-Treatment of Hypertension

Chronic kidney disease is more common than previously suspected and may be under diagnosed and under-treated in the United States, according to a new study by researchers at the Johns Hopkins Bloomberg School of Public Health. The findings indicate an estimated 5.6 million Americans have elevated serum creatinine levels in their blood, an indicator of chronic kidney disease. Seventy percent of those people also have high blood pressure. Hypertension is a leading factor in developing kidney disease.

While the majority of people in the study were treated for hypertension, only 11 percent reduced their blood pressure to recommended levels. The study, the first to examine the adequacy of blood pressure management in renal disease in the United States, appears in the May 14, 2001, issue of the Archives of Internal Medicine.

"The number of people with kidney failure in the U.S. is increasing and that is receiving a great deal of attention, but the number of people with chronic kidney disease is far greater," explains Josef Coresh, MD, PhD, associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. "There are 25 people with elevated serum creatinine for every person with prevalent end-stage renal failure. Most of these individuals are not aware of their kidney disease. We could be doing more to control this problem by improving hypertension treatment in these individuals and preventing kidney failure in the first place," says Dr. Coresh. He adds that people with chronic kidney disease are at greater risk of developing kidney failure, anemia, bone disease, and of dying. The annual cost of dialysis treatment was estimated to be more than $15 billion a year in 1997.

For this cross-sectional study, the researchers examined data from 16,589 adults who participated in the Third National Health and Nutrition Examination Survey between 1988 and 1994. Serum creatinine, which is a muscle breakdown product cleared by the kidneys, was measured in a blood sample. Blood pressure was measured during two separate evaluations. Anyone with an average systolic blood pressure greater than 140 or a diastolic pressure greater than 90 was considered hypertensive, as was anyone treated with blood pressure medications.

Overall, researchers found that high blood pressure, use of antihypertensive medications, older age, and diabetes were all associated with increased serum creatinine levels. Of those with hypertension, 75 percent received treatment; however, half of these individuals were treated with only one medication and the majority did not reduce their blood pressure to healthy levels. Only 11 percent of all hypertensives had a blood pressure below 130/85, which is recommended for people with kidney disease. Twenty-seven percent had a blood pressure less than 140/90, which is considered the normal level for healthy individuals. Thirty-six percent of those receiving medication were controlled to a blood pressure 140/90.

"Better education of patients and physicians about the problems associated with chronic kidney disease is needed. We know from several large studies that most individuals with kidney disease can have their hypertension controlled effectively. If we can face the challenge of improving hypertension treatment among Americans with chronic kidney disease we can reduce the number of people who require kidney dialysis or face other complications," adds Dr. Coresh.

The work of this study was started by G. Laura Wei, as a Master of Health Sciences student advised by Dr. Coresh at the Bloomberg School of Public Health. Geraldine McQuillan, PhD, Frederick L. Brancati, MD, MHS, Andrew S. Levey, MD, Camille Jones, MD, MPH, and Michael J. Klag, MD, MPH, contributed to the study.

Funding for the study was provided by grants from the National Institutes of Health and the General Clinical Research Center.