Rise in chronic kidney disease turns focus to risk factors

Public health officials and epidemiologists are trying to get a better grasp of the true prevalence of chronic kidney disease and associated risk factors because studies suggest that this condition is becoming increasingly common.

A paper in the March 2 Morbidity and Mortality Weekly Report analyzing data from the 1999-2004 National Health and Nutrition Examination Survey concluded that 16.8% of the population had some form of CKD.

This finding represented an increase of 15.9% from the 1988-1994 NHANES. This study also found having diabetes, cardiovascular disease and hypertension increased the risk, and that a majority of patients were at the early stages with very few having advanced disease.

"The majority are not even getting to the end stage, and we need to get a firmer handle on that," said Rashida Dorsey, PhD, senior author and an Epidemic Intelligence Service officer at the Centers for Disease Control and Prevention.

In addition, a study published in the April Journal of the American Society of Nephrology estimated that 9.5% of the population had a first-degree relative with end-stage renal disease. Those with this CKD risk factor were also more likely to have diabetes and be obese. African-Americans with a family history were also more likely to have impaired kidney function themselves. This finding, however, did not hold true with Caucasians.

"We found a very high prevalence of older adults in our population who reported a family member on dialysis or having had a transplant," William McClellan, MD, MPH, lead author and professor of medicine in the departments of medicine and epidemiology at Emory University in Atlanta.

The reasons for these rates are unclear, although many suspect it may be a combination of the increasing incidence of obesity and diabetes, the aging of the population, and more detection. Many specialists said these findings supported what they are seeing in their practices.

"CKD is on the rise," said Patrick McBride, MD, MPH, a family physician and professor at the University of Wisconsin School of Medicine and Public Health in Madison. "And this is going to get a lot worse before it gets any better."

These studies highlighted the urgent need to get an improved understanding of the true extent of this problem, experts say. Extensive data on those far enough along to need dialysis or a transplant is collected by the U.S. Renal Data System. However, no such system yet exists to track patients whose condition is less advanced.

"We now have a lot of information on the ESRD population. We have much less information on the prevalence of CKD," said Andrew Narva, MD, director of the National Kidney Disease Education Program. "These reports provide further evidence that such an effort is critical."

To fill this need, the CDC is establishing two pilot surveillance projects. Researchers will cull managed care and Veterans Affairs health system databases to create prevalence models and estimate the number of those who are diagnosed and undiagnosed, the medical system impact and quality of care received.

"We need to find out what's happening to these people. Are they getting what they should get? We may find out that more needs to be done than we thought," said Dr. Rajiv Saran, co-director of the Kidney Epidemiology and Cost Center at the University of Michigan, Ann Arbor, who will be leading the efforts at his institution. Neil R. Powe, MD, MPH, professor at the Johns Hopkins Bloomberg School of Public Health, is the principal investigator at that university.

The hope is that better data will lead to interventions that reduce the risk of this disease progressing, or, if it does move along, reduce the risk of early mortality. The majority of CKD patients are at stages I, II or III with few making it to IV or V, but this is not because the disease is reversed. Many die prematurely.

"Most people who have chronic kidney disease are much more likely to die of a cardiovascular event way before they ever need renal replacement therapy," said Biff F. Palmer, MD, a nephrologist and professor of internal medicine at the University of Texas Southwestern Medical Center. "Those who end up on dialysis may be the therapeutic successes."

Screening and prevention

Experts also want this better understanding of the disease and associated risk factors to lead to the greater use of strategies to prevent this disease from ever developing. For example, Dr. McClellan wants his results to prompt doctors who treat those with ESRD to reach out to their relatives.

"Those at risk could be identified very easily by linking through family members," said Dr. McClellan, who is also a research professor in the nephrology division at the University of Alabama.

Those who treat kidney disease are also hoping that better documentation of increasing CKD prevalence will lead to more detection, particularly in the primary care setting -- long before a patient needs dialysis or a transplant.

"That's where the patients are seen," said Cynda Ann Johnson, MD, a family physician and senior associate vice chancellor for clinical and translational research at East Carolina University in North Carolina. "They don't start out by going to the kidney specialist. We need to recognize the need for screening."

In order to make screening more targeted, a study in the Feb. 26 Archives of Internal Medicine, by researchers at the University of North Carolina, suggested that a scored questionnaire asking about age, gender and medical history can indicate who is more in need of a kidney function assessment.

The authors intend to further validate this tool in a community-based screening program.