Chronic Renal Insufficiency Cohort Research Articles

Plant Protein Intake is Associated With Fibroblast Growth Factor 23 and Serum Bicarbonate Levels in Patients With Chronic Kidney Disease: The Chronic Renal Insufficiency Cohort Study

Protein from plant, as opposed to animal, sources may be preferred in chronic kidney disease (CKD) because of the lower bioavailability of phosphate and lower nonvolatile acid load. Observational cross-sectional study. A total of 2,938 participants with CKD and information on their dietary intake at the baseline visit in the Chronic Renal Insufficiency Cohort Study. Percentage of total protein intake from plant sources (percent plant protein) was determined by scoring individual food items using the National Cancer Institute Diet History Questionnaire (DHQ). Metabolic parameters, including serum phosphate, bicarbonate (HCO₃), potassium, and albumin, plasma fibroblast growth factor 23 (FGF-23), and parathyroid hormone (PTH), and hemoglobin levels. We modeled the association between percent plant protein and metabolic parameters using linear regression. Models were adjusted for age, sex, race, diabetes status, body mass index, estimated glomerular filtration rate, income, smoking status, total energy intake, total protein intake, 24-hour urinary sodium concentration, use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, and use of diuretics. Higher percent plant protein was associated with lower FGF-23 (P = .05) and higher HCO₃ (P = .01) levels, but not with serum phosphate or parathyroid hormone concentrations (P = .9 and P = .5, respectively). Higher percent plant protein was not associated with higher serum potassium (P = .2), lower serum albumin (P = .2), or lower hemoglobin (P = .3) levels. The associations of percent plant protein with FGF-23 and HCO₃ levels did not differ by diabetes status, sex, race, CKD stage (2/3 vs. 4/5), or total protein intake (≤0.8 g/kg/day vs. >0.8 g/kg/day; P-interaction >.10 for each). This is a cross-sectional study; determination of percent plant protein using the Diet History Questionnaire has not been validated. Consumption of a higher percentage of protein from plant sources may lower FGF-23 and raise HCO₃ levels in patients with CKD.

Risk Factors for Peripheral Arterial Disease Among Patients With Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have an increased risk for developing peripheral arterial disease (PAD). The aim of this study was to examine the cross-sectional association between novel risk factors and prevalent PAD in patients with CKD. A total of 3,758 patients with estimated glomerular filtration rates of 20 to 70 ml/min/1.73 m(2) who participated in the Chronic Renal Insufficiency Cohort (CRIC) study were included in the present analysis. PAD was defined as an ankle-brachial index <0.9 or a history of arm or leg revascularization. After adjustment for age, gender, race, cigarette smoking, physical activity, history of hypertension and diabetes, pulse pressure, high-density lipoprotein cholesterol, estimated glomerular filtration rate, and CRIC clinical sites, several novel risk factors were significantly associated with PAD. For example, odds ratios for a 1-SD higher level of risk factors were 1.18 (95% confidence interval [CI] 1.08 to 1.29) for log-transformed high-sensitivity C-reactive protein, 1.18 (95% CI 1.08 to 1.29) for white blood cell count, 1.15 (95% CI 1.05 to 1.25) for fibrinogen, 1.13 (95% CI 1.03 to 1.24) for uric acid, 1.14 (95% CI 1.02 to 1.26) for glycosylated hemoglobin, 1.11 (95% CI 1.00 to 1.23) for log-transformed homeostasis model assessment of insulin resistance, and 1.35 (95% CI 1.18 to 1.55) for cystatin C. In conclusion, these data indicate that inflammation, prothrombotic state, oxidative stress, insulin resistance, and cystatin C were associated with an increased prevalence of PAD in patients with CKD. Further studies are warranted to examine the causal effect of these risk factors on PAD in patients with CKD.

Corrigendum: Aortic Pulse Pressure Is Associated With Carotid IMT in Chronic Kidney Disease: Report From Chronic Renal Insufficiency Cohort

Corrigendum: Aortic Pulse Pressure Is Associated With Carotid IMT in Chronic Kidney Disease: Report From Chronic Renal Insufficiency Cohort

Correlates of Osteoprotegerin and Association with Aortic Pulse Wave Velocity in Patients with Chronic Kidney Disease

Osteoprotegerin (OPG), a cytokine that regulates bone resorption, has been implicated in the process of vascular calcification and stiffness. Serum OPG was measured in 351 participants with chronic kidney disease (CKD) from one site of the Chronic Renal Insufficiency Cohort Study. Cortical bone mineral content (BMC) was measured by quantitative computed tomography in the tibia. Multivariable linear regression was used to test the association between serum OPG and traditional cardiovascular risk factors, measures of abnormal bone and mineral metabolism, and pulse wave velocity. Higher serum OPG levels were associated with older age, female gender, greater systolic BP, lower estimated GFR, and lower serum albumin. OPG was not associated with measures of abnormal bone or mineral metabolism including serum phosphorus, albumin-corrected serum calcium, intact parathyroid hormone, bone-specific alkaline phosphatase, or cortical BMC. Among 226 participants with concurrent aortic pulse wave velocity measurements, increasing tertiles of serum OPG were associated with higher aortic pulse wave velocity after adjustment for demographics, traditional vascular risk factors, and nontraditional risk factors such as estimated GFR, albuminuria, serum phosphate, corrected serum calcium, presence of secondary hyperparathyroidism, serum albumin, and C-reactive protein or after additional adjustment for cortical BMC in a subset (n = 161). These data support a strong relationship between serum OPG and arterial stiffness independent of many potential confounders including traditional cardiovascular risk factors, abnormal bone and mineral metabolism, and inflammation.

Measured GFR Does Not Outperform Estimated GFR in Predicting CKD-related Complications

Although many assume that measurement of glomerular filtration rate (GFR) using a marker such as iothalamate (iGFR) is superior to equation-estimated GFR (eGFR), each of these methods has distinct disadvantages. Because physicians often use renal function to guide the screening for various CKD-associated complications, one method to compare the clinical utility of iGFR and eGFR is to determine the strength of their association with CKD-associated comorbidities. Using a subset of 1214 participants in the Chronic Renal Insufficiency Cohort (CRIC) Study, we determined the cross-sectional associations between known complications of CKD and iGFR, eGFR estimated from serum creatinine (eGFR_Cr), and eGFR estimated from cystatin C (eGFR_cysC). We found that none of the measures of renal function strongly associated with CKD complications and that the relative strengths of associations varied according to the outcome of interest. For example, iGFR demonstrated better discrimination than eGFR_Cr and eGFR_cysC for outcomes of anemia and hemoglobin concentration; however, both eGFR_Cr and eGFR_cysC demonstrated better discrimination than iGFR for outcomes of hyperphosphatemia and phosphorus level. iGFR and eGFR had similar strengths of association with hyperkalemia/potassium level and with metabolic acidosis/bicarbonate level. In conclusion, iothalamate measurement of GFR is not consistently superior to equation-based estimations of GFR in explaining CKD-related comorbidities. These results raise questions regarding the conventional view that iGFR is the "gold standard" measure of kidney function.

Is There Something Better than the Best Marker of Kidney Function?

Measurement of kidney function is critical both for clinical decision-making and research. Direct measurement of GFR using urinary or plasma clearance of exogenously administered markers, such as 125I-iothalamate, is considered the gold standard method to assess kidney function. These procedures,

Cardiovascular Disease Among Hispanics and Non-Hispanics in the Chronic Renal Insufficiency Cohort (CRIC) Study

Hispanics are the largest minority group in the United States. The leading cause of death in patients with chronic kidney disease (CKD) is cardiovascular disease (CVD), yet little is known about its prevalence among Hispanics with CKD. We conducted cross-sectional analyses of prevalent self-reported clinical and subclinical measures of CVD among 497 Hispanics, 1638 non-Hispanic Caucasians, and 1650 non-Hispanic African Americans, aged 21 to 74 years, with mild-to-moderate CKD at enrollment in the Chronic Renal Insufficiency Cohort (CRIC) and Hispanic CRIC (HCRIC) studies. Measures of subclinical CVD included left ventricular hypertrophy (LVH), coronary artery calcification (CAC), and ankle-brachial index. Self-reported coronary heart disease (CHD) was lower in Hispanics compared with non-Hispanic Caucasians (18% versus 23%, P = 0.02). Compared with non-Hispanic Caucasians, Hispanics had a lower prevalence of CAC >100 (41% versus 34%, P = 0.03) and CAC >400 (26% versus 19%, P = 0.02). However, after adjusting for sociodemographic factors, these differences were no longer significant. In adjusted analyses, Hispanics had a higher odds of LVH compared with non-Hispanic Caucasians (odds ratio 1.97, 95% confidence interval, 1.22 to 3.17, P = 0.005), and a higher odds of CAC >400 compared with non-Hispanic African Americans (odds ratio, 2.49, 95% confidence interval, 1.11 to 5.58, P = 0.03). Hispanic ethnicity was not independently associated with any other CVD measures. Prevalent LVH was more common among Hispanics than non-Hispanic Caucasians, and elevated CAC score was more common among Hispanics than non-Hispanic African Americans. Understanding reasons for these racial/ethnic differences and their association with long-term clinical outcomes is needed.

Hemodynamic Correlates of Proteinuria in Chronic Kidney Disease

Brachial artery measures of BP are associated with increasing degrees of proteinuria. Whether central measures of BP or vascular stiffness are associated with increased risk of proteinuria in patients with chronic kidney disease (CKD) is unknown. Measurements of central and brachial artery BP, and aortic pulse wave velocity (PWV) were performed in a cross-sectional cohort of patients with CKD (n = 2144) from the Chronic Renal Insufficiency Cohort (CRIC) study to determine factors which predict increased risk of proteinuria. Multivariate analysis stratified by diabetes included age, ethnicity, gender, estimated glomerular filtration rate (GFR), waistline, smoking, heart rate, and medications to evaluate the relationship of hemodynamic factors and proteinuria. Brachial artery systolic BP (SBP) was important as an explanatory factor for variations in proteinuria among both diabetics (R(2) = 0.40, P < 0.0001) and non diabetics (R(2) = 0.38, P < 0.001). Measures of peripheral pulse pressure (PP), central SBP, and central pulse pressure added little to the explained variation in proteinuria beyond brachial artery SBP, whereas PWV as a measure of vascular stiffness incrementally accounted for a significant portion of variation in proteinuria beyond that explained by brachial artery SBP in diabetics (R(2) = 0.42, P < 0.001) but not non diabetics. Brachial artery SBP and PWV are both associated with variations in proteinuria in patients with CKD.

Relationship of Estimated GFR and Coronary Artery Calcification in the CRIC (Chronic Renal Insufficiency Cohort) Study

Coronary artery calcification (CAC) is associated with increased mortality risk in the general population. Although individuals with chronic kidney disease (CKD) are at markedly increased mortality risk, the incidence, prevalence, and prognosis of CAC in CKD are not well understood. Cross-sectional observational study. Analysis of 1,908 participants who underwent coronary calcium scanning as part of the multiethnic CRIC (Chronic Renal Insufficiency Cohort) Study. Estimated glomerular filtration rate (eGFR) computed using the Modification of Diet in Renal Disease (MDRD) Study equation, stratified by race, sex, and diabetic status. eGFR was treated as a continuous and a categorical variable compared with the reference value of >60 mL/min/1.73 m(2). CAC detected using computed tomography (CT) using either an Imatron C-300 electron beam computed tomography (CT) scanner or multidetector CT scanner. CAC was computed using Agatston score as a categorical variable. Analyses were performed using ordinal logistic regression. We found a strong and graded relationship between lower eGFR and increasing CAC. In unadjusted models, ORs increased from 1.68 (95% CI, 1.23-2.31) for eGFR of 50-59 mL/min/1.73 m(2) to 2.82 (95% CI, 2.06-3.85) for eGFR <30 mL/min/1.73 m(2). Multivariable adjustment only partially attenuated the results (OR, 1.53; 95% CI, 1.07-2.20) for eGFR <30 mL/min/1.73 m(2). Use of eGFR rather than measured GFR. We showed a graded relationship between severity of CKD and CAC independent of traditional risk factors. These findings support recent guidelines that state that if vascular calcification is present, it should be considered as a complementary component to be included in the decision making required for individualizing CKD treatment.

CKD in Hispanics: Baseline Characteristics From the CRIC (Chronic Renal Insufficiency Cohort) and Hispanic-CRIC Studies

Little is known regarding chronic kidney disease (CKD) in Hispanics. We compared baseline characteristics of Hispanic participants in the Chronic Renal Insufficiency Cohort (CRIC) and Hispanic-CRIC (H-CRIC) Studies with non-Hispanic CRIC participants. Cross-sectional analysis. Participants were aged 21-74 years with CKD using age-based estimated glomerular filtration rate (eGFR) at enrollment into the CRIC/H-CRIC Studies. H-CRIC included Hispanics recruited at the University of Illinois in 2005-2008, whereas CRIC included Hispanics and non-Hispanics recruited at 7 clinical centers in 2003-2007. Race/ethnicity. Blood pressure, angiotensin-converting enzyme (ACE)-inhibitor/angiotensin receptor blocker (ARB) use, and CKD-associated complications. Demographic characteristics, laboratory data, blood pressure, and medications were assessed using standard techniques and protocols. Of H-CRIC/CRIC participants, 497 were Hispanic, 1,650 were non-Hispanic black, and 1,638 were non-Hispanic white. Low income and educational attainment were nearly twice as prevalent in Hispanics compared with non-Hispanics (P < 0.01). Hispanics had self-reported diabetes (67%) more frequently than non-Hispanic blacks (51%) and whites (40%; P < 0.01). Blood pressure >130/80 mm Hg was more common in Hispanics (62%) than blacks (57%) and whites (35%; P < 0.05), and abnormalities in hematologic, metabolic, and bone metabolism parameters were more prevalent in Hispanics (P < 0.05), even after stratifying by entry eGFR. Hispanics had the lowest use of ACE inhibitors/ARBs among the high-risk subgroups, including participants with diabetes, proteinuria, and blood pressure >130/80 mm Hg. Mean eGFR was lower in Hispanics (39.6 mL/min/1.73 m(2)) than in blacks (43.7 mL/min/1.73 m(2)) and whites (46.2 mL/min/1.73 m(2)), whereas median proteinuria was higher in Hispanics (protein excretion, 0.72 g/d) than in blacks (0.24 g/d) and whites (0.12 g/d; P < 0.01). Generalizability; observed associations limited by residual bias and confounding. Hispanics with CKD in the CRIC/H-CRIC Studies are disproportionately burdened with lower socioeconomic status, more frequent diabetes mellitus, less ACE-inhibitor/ARB use, worse blood pressure control, and more severe CKD and associated complications than their non-Hispanic counterparts.

Fibroblast growth factor 23 is elevated before parathyroid hormone and phosphate in chronic kidney disease

Fibroblast growth factor 23 (FGF23) regulates phosphorus metabolism and is a strong predictor of mortality in dialysis patients. FGF23 is thought to be an early biomarker of disordered phosphorus metabolism in the initial stages of chronic kidney disease (CKD). We measured FGF23 in baseline samples from 3879 patients in the Chronic Renal Insufficiency Cohort study, which is a diverse cohort of patients with CKD stage 2-4. Mean serum phosphate and median parathyroid hormone (PTH) levels were in the normal range, but median FGF23 was markedly greater than in healthy populations, and increased significantly with decreasing estimated glomerular filtration rate (eGFR). High levels of FGF23, defined as being above 100 RU/ml, were more common than secondary hyperparathyroidism and hyperphosphatemia in all strata of eGFR. The threshold of eGFR at which the slope of FGF23 increased was significantly higher than the corresponding threshold for PTH based on non-overlapping 95% confidence intervals. Thus, increased FGF23 is a common manifestation of CKD that develops earlier than increased phosphate or PTH. Hence, FGF23 measurements may be a sensitive early biomarker of disordered phosphorus metabolism in patients with CKD and normal serum phosphate levels.

175 Recruitment of Hispanics with CKD: The Hispanic Chronic Renal Insufficiency Cohort Study Experience

175 Recruitment of Hispanics with CKD: The Hispanic Chronic Renal Insufficiency Cohort Study Experience

Diuretics, calciuria and secondary hyperparathyroidism in the Chronic Renal Insufficiency Cohort

Secondary hyperparathyroidism is a common complication of chronic kidney disease (CKD) that is associated with bone disease, cardiovascular disease and death. Pathophysiological factors that maintain secondary hyperparathyroidism in advanced CKD are well-known, but early mechanisms of the disease that can be targeted for its primary prevention are poorly understood. Diuretics are widely used to control volume status and blood pressure in CKD patients but are also known to have important effects on renal calcium handling, which we hypothesized could alter the risk of secondary hyperparathyroidism. We examined the relationship of diuretic treatment with urinary calcium excretion, parathyroid hormone (PTH) levels and prevalence of secondary hyperparathyroidism (PTH ≥ 65 pg/mL) in a cross-sectional study of 3616 CKD patients in the Chronic Renal Insufficiency Cohort. Compared with no diuretics, treatment with loop diuretics was independently associated with higher adjusted urinary calcium (55.0 versus 39.6 mg/day; P < 0.001), higher adjusted PTH [67.9, 95% confidence interval (CI) 65.2-70.7 pg/mL, versus 52.8, 95% CI 51.1-54.6 pg/mL, P < 0.001] and greater odds of secondary hyperparathyroidism (odds ratio 2.1; 95% CI 1.7-2.6). Thiazide monotherapy was associated with lower calciuria (25.5 versus 39.6 mg/day; P < 0.001) but only modestly lower PTH levels (50.0, 95% CI 47.8-52.3, versus 520.8, 95% CI 51.1-54.6 pg/mL, P = 0.04) compared with no diuretics. However, coadministration of thiazide and loop diuretics was associated with blunted urinary calcium (30.3 versus 55.0 mg/day; P <0.001) and odds of hyperparathyroidism (odds ratio 1.3 versus 2.1; P for interaction = 0.05) compared with loop diuretics alone. Loop diuretic use was associated with greater calciuria, PTH levels and odds of secondary hyperparathyroidism compared to no treatment. These associations were attenuated in patients who were coadministered thiazides. Diuretic choice is a potentially modifiable determinant of secondary hyperparathyroidism in CKD.

Renal Function Outcomes After Laparoscopic Renal Cryoablation

Laparoscopic cryoablation (LCA) has emerged as an alternative to conventional surgery for the management of a T(1) renal mass; however, only few data are available on its functional outcomes. We assessed renal function changes after LCA in patients with normal renal function (NRF) and preexisting chronic renal insufficiency (CRI). Data of consecutive patients who were undergoing LCA between 2000 and 2008 at Duke University Medical Center were analyzed. Renal function parameters were obtained preoperatively, at discharge, and at 6, 12, and 24 months postoperatively. Serum creatinine (sCr) levels and estimated glomerular filtration rates (eGFR) were compared over a 2-year follow-up. Of 67 patients, 22 (33%) had CRI at baseline. These patients were older, had larger tumors (2.5 vs 2.0 cm, P=0.039), and a higher incidence of multiple lesions (22.7% vs 4.4%, P=0.034). Compared with baseline, sCr was significantly increased and eGFR declined at discharge, 6, 12, and 24 months in both NRF and CRI groups. Median sCr increase was 0.1 mg/mL, eGFR declined by 4.2 mg/mL/1.73 m(2) in the CRI cohort and up to 8.8 mg/mL/1.73m(2) in NRF patients (all P<0.05) during the follow-up. Compared with baseline, however, no significant changes were noted in the distribution of CRI categories at any time (all P>0.05). A minimal decline in renal function can be appreciated in patients undergoing LCA at midterm follow-up. This decline is no higher in CRI than in NRF patients. LCA offers excellent renal function outcomes at 2 years follow-up. Specifically, in patients with CRI, LCA offers excellent preservation of renal function.

Advances in Nitrogen Management for Water Quality

Limited studies have assessed the resting 12-lead electrocardiogram (ECG) as a screening test in intermediate risk populations. We evaluated whether a panel of common ECG parameters are independent predictors of mortality risk in a prospective cohort of participants with CKD. The Chronic Renal Insufficiency Cohort (CRIC) study enrolled 3939 participants with eGFR&lt;70 ml/min per 1.73 m² from June 2003 to September 2008. Over a median follow-up of 7.5 years, 750 participants died. After adjudicating the initial 497 deaths, we identified 256 cardiovascular and 241 noncardiovascular deaths. ECG metrics were independent risk markers for cardiovascular death (hazard ratio, 95% confidence interval): PR interval ≥200 ms (1.62, 1.19–2.19); QRS interval 100–119 ms (1.64, 1.20–2.25) and ≥120 ms (1.75, 1.17–2.62); corrected QT (QTc) interval ≥450 ms in men or ≥460 ms in women (1.72, 1.19–2.49); and heart rate 60–90 beats per minute (1.21, 0.89–1.63) and ≥90 beats per minute (2.35, 1.03–5.33). Most ECG measures were stronger markers of risk for cardiovascular death than for all-cause mortality or noncardiovascular death. Adding these intervals to a comprehensive model of cardiorenal risk factors increased the C-statistic for cardiovascular death from 0.77 to 0.81 (<i>P</i>&lt;0.001). Furthermore, adding ECG metrics to the model adjusted for standard risk factors resulted in a net reclassification of 12.1% (95% confidence interval 8.1%–16.0%). These data suggest common ECG metrics are independent risk factors for cardiovascular death and enhance the ability to predict death events in a population with CKD.

Symptoms Characteristic of Heart Failure Among CKD Patients Without Diagnosed Heart Failure

Background Epidemiological studies typically diagnose heart failure (HF) at the time of hospitalization, and have not evaluated the prevalence of HF symptoms in CKD patients without a prior HF diagnosis. Methods and Results We modified the Kansas City Cardiomyopathy Questionnaire (KCCQ) to detect and quantify symptoms characteristic of HF (dyspnea, edema, and fatigue) among 2883 chronic kidney disease (CKD) patients without diagnosed heart failure in the Chronic Renal Insufficiency Cohort (CRIC). The KCCQ is a 23-item instrument that quantifies the impact of dyspnea, fatigue, and edema on physical, social, and emotional functions (scored 0 to 100). The median KCCQ score was 92, and 25% had KCCQ scores <75. Compared with cystatin C‑based estimated glomerular filtration rate >50 mL·min·1.73m 2 (reference), estimated glomerular filtration rate 40 to 50, 30 to 40, and <30 were independently associated with lower KCCQ scores (<75); adjusted odds ratios and (95% CI): 1.38 (1.06–1.78), 1.39 (1.09–1.82), and 2.15 (1.54–3.00), respectively. Lower hemoglobin (Hb) levels also had independent associations with KCCQ <75: Hb >14 g/dL (reference), Hb 13 to 14 g/dL (1.03; 0.76–1.40), Hb 12 to 13 g/dL (1.41; 1.04–1.91), Hb 11 to 12 g/dL (1.56; 1.12–2.16); and Hb <1 g/dL (1.65; 1.15–2.37). Conclusion CKD patients without diagnosed HF have a substantial burden of symptoms characteristic of HF, particularly among those with lower estimated glomerular filtration rate and hemoglobin levels.

Central Pulse Pressure in Chronic Kidney Disease

Central pulse pressure (PP) can be noninvasively derived using the radial artery tonometric methods. Knowledge of central pressure profiles has predicted cardiovascular morbidity and mortality in several populations of patients, particularly those with known coronary artery disease and those receiving dialysis. Few data exist characterizing central pressure profiles in patients with mild-moderate chronic kidney disease who are not on dialysis. We measured central PP cross-sectionally in 2531 participants in the Chronic Renal Insufficiency Cohort Study to determine correlates of the magnitude of central PP in the setting of chronic kidney disease. Tertiles of central PP were &lt;36 mm Hg, 36 to 51 mm Hg, and &gt;51 mm Hg with an overall mean (±SD) of 46±19 mm Hg. Multivariable regression identified the following independent correlates of central PP: age, sex, diabetes mellitus, heart rate (negatively correlated), glycosylated hemoglobin, hemoglobin, glucose, and parathyroid hormone parathyroid hormone concentrations. Additional adjustment for brachial mean arterial pressure and brachial PP showed associations for age, sex, diabetes mellitus, weight, and heart rate. Discrete intervals of brachial PP stratification showed substantial overlap within the associated central PP values. The large size of this unique chronic kidney disease cohort provides an ideal situation to study the role of brachial and central pressure measurements in kidney disease progression and cardiovascular disease incidence.

Chronic Kidney Disease in Patients with Cognitive Impairment: A Marker of Microvascular Damage or an Independent Risk Factor?

Evaluation of: Yaffe K, Ackerson L, Tamura MK et al.: Chronic kidney disease and cognitive function in older adults: findings from the chronic renal insufficiency cohort cognitive study. J. Am. Geriatr. Soc. 58, 338–345 (2010). The effect of chronic kidney disease (CKD) on cognition is unclear, especially in less severe forms of the disease. Studies are needed to clarify whether CKD is associated with a particular pattern of cognitive dysfunction, to understand the cognitive domains affected, and to clarify the mechanisms through which CKD might be affecting brain function. The authors comment on a cross-sectional study in a well-characterized cohort of patients with CKD that examined the effect of different levels of kidney function on cognitive impairment. The methodology of the study and the potential mechanisms underlying cognitive impairment seen in patients with CKD are discussed.

Heritability of Measures of Kidney Disease Among Zuni Indians: The Zuni Kidney Project

The long-term goal of the GKDZI (Genetics of Kidney Disease in Zuni Indians) Study is to identify genes, environmental factors, and genetic-environmental interactions that modulate susceptibility to renal disease and intermediate phenotypes. A community-based participatory research approach was used to recruit family members of individuals with kidney disease. The study was conducted in the Zuni Indians, a small endogamous tribe located in rural New Mexico. We recruited members of extended families, ascertained through a proband with kidney disease and at least 1 sibling with kidney disease. 821 participants were recruited, comprising 7,702 relative pairs. PREDICTOR OUTCOMES & MEASUREMENTS: Urine albumin-creatinine ratio (UACR) and hematuria were determined in 3 urine samples and expressed as a true ratio. Glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease (MDRD) Study equation modified for American Indians. Probands were considered to have kidney disease if UACR was >or=0.2 in 2 or more of 3 spot urine samples or estimated GFR was decreased according to the CRIC (Chronic Renal Insufficiency Cohort) Study criteria. Kidney disease was identified in 192 participants (23.4%). There were significant heritabilities for estimated GFR, UACR, serum creatinine, serum urea nitrogen, and uric acid and a variety of phenotypes related to obesity, diabetes, and cardiovascular disease. There were significant genetic correlations of some kidney-related phenotypes with these other phenotypes. Limitations include absence of renal biopsy, possible misclassification bias, lack of direct GFR measurements, and failure to include all possible environmental interactions. Many phenotypes related to kidney disease showed significant heritabilities in Zuni Indians, and there were significant genetic correlations with phenotypes related to obesity, diabetes, and cardiovascular disease. The study design serves as a paradigm for the conduct of research in relatively isolated, endogamous, underserved populations.

Chronic kidney disease and prevalent atrial fibrillation: The Chronic Renal Insufficiency Cohort (CRIC)

The epidemiology of atrial fibrillation (AF) has been mainly investigated in patients with end-stage renal disease, with limited data on less advanced chronic kidney disease (CKD) stages. A total of 3,267 adult participants (50% non-Hispanic blacks, 46% women) with CKD from the Chronic Renal Insufficiency Cohort were included in this study. None of the study participants had been on dialysis. Those with self-identified race/ethnicity other than non-Hispanic black or white (n = 323) or those without electrocardiographic data (n = 22) were excluded. Atrial fibrillation was ascertained by a 12-lead electrocardiogram and self-report. Age-, sex-, and race/ethnicity-specific prevalence rates of AF were estimated and compared between subgroups. Cross-sectional associations and correlates with prevalent AF were examined using unadjusted and multivariable-adjusted logistic regression analysis. The mean estimated glomerular filtration rate was 43.6 (+/-13.0) mL/(min 1.73 m(2)). Atrial fibrillation was present in 18% of the study population and in >25% of those > or =70 years old. In multivariable-adjusted models, 1-SD increase in age (11 years) (odds ratio 1.27, CI 95% 1.13-1.43, P < .0001), male [corrected] sex (0.80, 0.65-0.98, P = .0303), smoking (former vs never) (1.34, 1.08-1.66, P = .0081), history of heart failure (3.28, 2.47-4.36, P < .001), and history of cardiovascular disease (1.94, 1.56-2.43, P < .0001) were significantly associated with AF. Race/ethnicity, hypertension, diabetes, body mass index, physical activity, education, high-sensitivity C-reactive protein, total cholesterol, and alcohol intake were not significantly associated with AF. An estimated glomerular filtration rate <45 mL/(min 1.73 m(2)) was associated with AF in an unadjusted model (1.35, 1.13-1.62, P = .0010), but not after multivariable adjustment (1.12, 0.92-1.35, P = .2710). Nearly 1 in 5 participants in Chronic Renal Insufficiency Cohort, a national study of CKD, had evidence of AF at study entry, a prevalence similar to that reported among patients with end-stage renal disease and 2 to 3 times of that reported in the general population. Risk factors for AF in this CKD population do not mirror those reported in the general population.