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Effects of Chronic Kidney Disease in Adults Study: CRIC

The Chronic Renal Insufficiency Cohort (CRIC) Study is one of the largest and longest ongoing studies looking at the causes, frequency, and consequences of chronic kidney disease (CKD) in the United States. The NIDDK supports the CRIC Study to better understand

  • what makes CKD worsen and result in complete loss of kidney function or kidney failure.
  • the link between CKD and cardiovascular disease (heart and blood vessel disease or CVD), that is commonly seen in people with CKD.

The study is also building on 15 years of information gathered by looking at the effects of CKD in older people, since they make up a large part of the CKD population.

Approximately 15 percent of Americans have CKD, and close to 700,000 people in the United States depend on kidney replacement therapy (dialysis or transplant) to treat kidney failure. The costs of CKD and kidney failure in the United States billed to Medicare is more than $90 billion per year. Treatment of kidney failure alone costs about $33 billion each year, according to the U.S. Renal Data System. Understanding the risk factors that cause CKD to worsen and why patients with CKD frequently have CVD will help researchers design clinical trials to test treatments that may reduce the impact of CKD.


The CRIC Study investigators have made important discoveries. One key finding is that African Americans who have a gene called APOL1 are about one and a half to two times more likely to experience a big loss of kidney function or kidney failure compared to Caucasians. This finding has stimulated additional research to determine how this gene increases risk of poor outcomes in African Americans with CKD.

Another key finding from CRIC was the discovery that high levels of a hormone called fibroblast growth factor 23 (FGF 23)—which controls the amount of phosphorus, a mineral in the blood—are linked to a higher risk of kidney failure and death. This finding led to a pilot clinical trial, supported by the NIDDK, to test whether FGF 23 and phosphorus levels can be lowered by medicines. A larger study will be necessary to find out whether lowering FGF 23 and phosphorus levels can slow the worsening of CKD and lower the risk of CVD and death.

A third important finding is that increased sodium in a person’s a urine—a measure of salt intake from their diet—was associated with increased risk of CVD.  Whether reducing dietary salt intake lowers the chances that a CKD patient will also have CVD could be tested in a clinical trial.

Study Size, Participant Demographics, and Study Design

The CRIC Study has been funded since 2001. The multicenter study enrolled more than 3,900 adults with CKD from 2003 to 2008 and many continue to be followed. All participants had CKD when they joined the study, but the severity of the disease (how well their kidneys functioned) varied. Half of the participants also had diabetes. The study includes both men and women and is ethnically and racially diverse, including about the same number of Caucasian and African-American participants (42 percent each). About 12 percent of the study participants are Hispanic/Latino. Participants continue to receive normal medical care from their own health care providers, but do not receive additional medical care as a part of the study. A follow-up study, the Hispanic Chronic Renal Insufficiency Cohort Study (HCRIC), enrolled an additional Hispanic/Latino 327 participants at a single clinical site from 2005 to 2008.

During the CRIC Study, participants had their height, weight, blood pressure, and heart rates measured. Blood and urine samples were taken at the beginning of the study and at yearly clinical visits to study the extent of the participants’ kidney and heart disease. As the study advanced and was extended into a second phase, researchers looked at whether participants had eye disease due to diabetes, high blood pressure, and other health problems. The study also collected information from participants each year on medical history, including medicines taken, weight, quality of life, diet, and physical activity levels. Some participants had their blood pressure taken more often and received other tests, such as eye scans.

An additional 1,500 participants were recruited into the third phase of the study, between July 2013 and August 2015, which focused on older adults. Researchers are currently analyzing the results from this part of the study. A fourth phase of the study will begin in mid-2018.

The CRIC Study’s Scientific and Data Coordinating Center is located at the University of Pennsylvania. The study is currently conducted by researchers at 11 clinical sites in the United States:

  • Case Western Reserve University, Cleveland, Ohio
  • Cleveland Clinic, Cleveland, Ohio
  • Johns Hopkins Medical Institutions, Baltimore, Maryland
  • Kaiser Permanente Northern California, Oakland, California
  • MetroHealth Cleveland, Cleveland, Ohio
  • Tulane University, New Orleans, Louisiana
  • University of Illinois at Chicago, Chicago, Illinois
  • University of Maryland Medical System, Baltimore, Maryland
  • University of Michigan, Ann Arbor, Michigan
  • University of Pennsylvania, Philadelphia, Pennsylvania
  • Wayne State University, Detroit, Michigan

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