Kidney Disease Research Updates
Fall 2009

Lower Socioeconomic and Education Status Associated with Reduced Kidney Function and More CVD
Baseline Results of the CRIC Study Reported

Researchers with the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)-funded Chronic Renal Insufficiency Cohort (CRIC) Study have reported participants' baseline characteristics and associated kidney function data.

With the goal of identifying risk factors for chronic kidney disease (CKD) and cardiovascular disease (CVD) progression, the CRIC Study is the largest NIDDK-funded prospective cohort of CKD patients.

"The strength of the CRIC Study lies in the diverse characteristics of the assembled cohort and the comprehensive data-collection activities that have been designed to address gaps in our understanding of CKD-associated morbidity and mortality and to identify potential targets for trials of preventative therapies," wrote James P. Lash, M.D., associate professor of medicine, University of Illinois at Chicago, and co-authors, in their report, which appeared in the August 2009 issue of the Clinical Journal of the American Society of Nephrology.

Slowing CKD and CVD

The prevalence of CKD has risen dramatically during the past 30 years. An estimated 15 million adults in the United States have a glomerular filtration rate (GFR) of 60 or less. GFR is a measure of the kidneys’ filtering capacity. Although CKD damage is usually not reversible, treatment can slow its progression. People with CKD are at higher risk of CVD, which accounts for nearly half of all deaths among hemodialysis patients.

By studying people with early-stage CKD, the CRIC Study hopes to identify better treatments and interventions to slow disease progression.

The CRIC Study enrolled 3,612 participants, ages 21 to 74, with mild to moderate CKD. At annual visits, researchers at seven clinical centers are collecting participants’ health information, including data regarding kidney function and the development of CVD. A subgroup of participants is undergoing more intensive testing, which includes iothalamate clearance studies to measure GFR and electron-beam tomography to evaluate coronary heart disease. The study will continue to follow participants after progression to kidney failure and treatment with dialysis or transplantation.

Baseline Characteristics

At the baseline visit, researchers collected data regarding sociodemographic characteristics, medical history, lifestyle behaviors, and current medications. Body mass index (BMI)—an index of weight adjusted for height—blood pressure, and heart activity measured through electrocardiogram were assessed. Researchers also asked questions about quality of life, diet, physical activity, and mental health status.

At baseline, among CRIC Study participants,

• 45 percent were Caucasian, 46 percent were African American, 5 percent were Hispanic/Latino, and 4 percent were Asian, Pacific Islander, or Native American
• about 33 percent had completed a college education; 28 percent had annual incomes less than $20,000
• nearly 90 percent had a history of hypertension and 70 percent were taking high blood pressure medication
• average BMI was 32.1, with more than half considered obese

• older, female, and Hispanic/Latino
• less educated, with annual incomes of less than $20,000
• more likely to have a BMI greater than 30
• more likely to have a history of cigarette smoking
• more likely to have high blood pressure, diabetes, CVD, and higher urine protein

• less likely to be Caucasian
• less likely to have a college education
• almost twice as likely to have CVD
• more likely to have annual incomes less than $20,000
• more likely to have high blood pressure and obesity
• more likely to have lower estimated GFR and higher urine protein

Modifiable Risk Factors

"Noteworthy is the high prevalence of several potentially modifiable risk factors in this CKD cohort," wrote Lash and co-authors, referring to rates of high blood pressure, obesity, and smoking among study participants. "Longitudinal follow-up of CRIC participants will afford a more rigorous assessment of these newly recognized but less studied risk factors on CVD and CKD outcomes."

For more information about the CRIC Study, visit www.cristudy.org.

Fact sheets and easy-to-read booklets about kidney disease are available from the NIDDK. For more information and to obtain copies, visit www.kidney.niddk.nih.gov.

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NIH Publication No. 10–4531
October 2009