NIH expands study to better understand kidney disease progression

Researchers from the Chronic Renal Insufficiency Cohort (CRIC) study are embarking on another five years of work to identify risk factors for progression of early stage chronic kidney disease (CKD), better understand the importance of reduced kidney function in older persons, and learn what role CKD may play in other illnesses that require hospitalization. CRIC is supported by the National Institutes of Health.

A major goal of the next five years is to recruit 1,500 people to the existing group of nearly 4,000 study participants. According to Dr. Harold Feldman, the principal investigator of the study’s Scientific and Data Coordinating Center at the University of Pennsylvania, Philadelphia, this additional time will allow researchers to collect more data needed to explore and build upon findings compiled over the past 10 years, and examine in much greater detail the broad range of illnesses experienced by people with CKD.

“The original volunteers have aged since the study began. By extending the study, we’re able to look more closely at an older population – a crucial time since most people who develop kidney failure that requires dialysis or a kidney transplant do so in their early 60s,” said Dr. Robert Star, director of the Division of Kidney, Urologic, and Hematologic Diseases at NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). “Studying older individuals with CKD is an area of considerable interest, so unlike the original cohort where participants were broadly aged — between 21 and 74 years at study entry — those invited to join now will be between the ages of 45 and 79.”

Dialysis is a treatment to filter wastes and excess fluid from the blood, a task normally performed by the kidneys. Most people with kidney failure are attached to a dialysis machine for three to four hours at a time, three times per week.

Another important feature of the new study participants is that they will have better kidney function or less severe disease — known as mild to moderate CKD — than the original study participants. They will also be screened for protein in the urine, a sign of kidney damage. Most of the U.S. population with CKD has mild to moderate disease.

“By more closely studying a group with better kidney function, we can try to learn how to prevent kidney disease,” Star said. “We want to better understand the risk factors for worsening of kidney function to design new strategies for treatment of CKD and its complications.”

Lastly, although the CRIC study investigators carefully studied the association of cardiovascular disease with CKD, recent analyses revealed that many patients were hospitalized frequently for respiratory and digestive illnesses. This finding led study investigators to plan to collect more information on the impact of CKD on hospitalizations, according to Star. “Together with expanding the existing study population to include additional older patients and earlier stages of CKD, this fresh approach amounts to a regeneration of the CRIC study that will map out a whole new way to evaluate the impact of CKD,” he said. “Although the relationship between CKD and cardiovascular disease is still a major focus, since it’s the big killer among CKD patients, the CRIC study will examine more closely these other related illnesses that impact so significantly on patients’ overall functioning and health.”

Feldman added that the study will continue, in accordance with applicable data privacy laws and policies, to send study data and specimens from all participants to the Central NIDDK Repositories. All data and specimens are made available to a wider research community to expand the usefulness of the study.

An estimated 20 million or more American adults have CKD, and over 400,000 people in the United States and 2 million worldwide depend on dialysis to treat kidney failure. CKD costs the nation $44 billion per year, or roughly 18 percent of total Medicare expenditures, and kidney failure carries a cost of $33 billion, according to NIH’s U.S. Renal Data System.

The CRIC study is one of the largest and longest ongoing studies of CKD epidemiology in the U.S. It is a collaboration among 13 U.S. clinical sites – Case Western Reserve University, Cleveland; the Cleveland Clinic, Cleveland; Johns Hopkins Medical Institutions, Baltimore; Kaiser Permanente Northern California, Oakland, Calif.; MetroHealth Cleveland, Cleveland; St. Johns Medical Center, Detroit; Tulane University, New Orleans; University of California San Francisco, San Francisco, Calif.; University of Illinois, Champagne, Ill.; University of Maryland, College Park, College Park, Md.; University of Michigan, Ann Arbor, Mich.; University of Pennsylvania, Philadelphia; and Wayne State University, Detroit. The study’s Scientific and Data Coordinating Center is at the University of Pennsylvania.

New findings have emerged from the CRIC study already, including the discovery that a high level of fibroblast growth factor 23, a hormone that regulates the amount of phosphate in the blood, has been linked to a significantly increased risk of death and kidney failure.

The CRIC study (ClinicalTrials.gov number: NCT00304148) is supported under NIH grant U01DK060990. For more information, including published results, visit www.cristudy.org.

The NIDDK, a component of the NIH, conducts and supports research on diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition and obesity; and kidney, urologic and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe and disabling conditions affecting Americans. For more information about the NIDDK and its programs, see www.niddk.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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