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. Author manuscript; available in PMC: 2011 May 5.
Published in final edited form as: Nephrol Nurs J. 2010 MAR-APR;37(2):133–142.

Identification of Modifiable Chronic Kidney Disease Risk Factors by Gender In an African-American Metabolic Syndrome Cohort

Loretta Jackson Brown 1, Patricia C Clark 2, Karen A Armstrong 3, Zhao Liping 4, Sandra B Dunbar 5
PMCID: PMC3088518  NIHMSID: NIHMS284551  PMID: 20462073

Abstract

African Americans experience a disproportionately greater burden of chronic kidney disease (CKD) Stage 5 than Caucasians and other minority groups. Precursors to CKD may also be components of metabolic syndrome. This study identified modifiable risk factors for CKD in an African-American metabolic syndrome cohort and compared results by gender. Both men and women (52%) had blood pressure values of 130/80 or higher, impaired fasting glucose levels of 100 to 125 mg/dL (25.5%), and body mass index greater than 25 (98.9%). There was no significant difference between genders. Appropriate clinical management of these factors may prevent or delay the onset of CKD.

The prevalence of chronic kidney disease (CKD) has increased significantly over the last several decades in the U.S. A comparison of data from the 1988 to 1994 National Health and Nutrition Examination Survey (NHANES) and the 1999 to 2004 NHANES suggest that the prevalence of CKD in the U.S. had increased from 14.5% to 16.8% between these time frames (Coresh, Astor, Greene, Eknoyan, & Levey, 2003). Undiagnosed and untreated, CKD can progress to end stage renal disease (ESRD), which is associated with high mortality, high morbidity, and disability (United States Renal Data System [USRDS], 2009). African Americans are disproportionately affected by CKD Stage 5 (Coresh et al., 2003). Although the overall prevalence of moderate or end stage CKD is not greater among African Americans when compared to non-Hispanic Whites, African Americans tend to progress to end stage disease at five times the rate of non-Hispanic Whites (Hsu, Lin, Vittinghoff, & Shipak, 2003; Tarver-Carr et al., 2002). Because kidney disease often progresses to end stage CKD for African Americans, the identification of precursors of CKD is important to prevent or delay the progression of disease (Fox et al., 2004).

Almost one-half (44%) of the excess risk of CKD among African-American adults can be attributed to modifiable risk factors (Tarver-Carr et al., 2002). Diabetes mellitus, high blood pressure (BP), elevated body mass index (BMI), dyslipidemia, and smoking have been identified as risk factors that increase the susceptibility for CKD or the progression of CKD (National Kidney Foundation [NKF], 2002). Of these, the first four are also components of a condition termed metabolic syndrome, a clustering of cardiovascular risk factors. One-fourth of U.S. adults, 20 years of age or older, meet the clinical criteria for the diagnosis of metabolic syndrome (Park et al., 2003). Metabolic syndrome is believed to be an independent risk factor for CKD (Chen et al., 2004; Kurella, Lo, & Chertow, 2005; Rashidi, Ghanbarian, & Azizi, 2007).

Components of the metabolic syndrome or disorders that occur from the progression of metabolic syndrome to disease are also risk factors for developing CKD. Gender has been proposed as a non-modifiable predictor of risk for initiation or progression of CKD (Eriksen & Ingebretsen, 2006; Jafar et al., 2003; Johnson, Thorp, Yang, Charansonney, & Smith, 2007; Neugarten, Acharya, & Silbiger, 2000). A greater incidence of end stage CKD has been reported in men (USRDS, 2009). Female gender has been associated with a slower progression of CKD and better kidney conservation and patient health outcomes (Eriksen & Ingebretsen, 2006). Although African Americans have an increased risk for CKD, several studies have found that most are unaware of their increased risk for developing CKD (Vassalotti, Gracz-Weinstein, Gannon, & Brown, 2006; Waterman, Browne, Waterman, Gladstone, & Hostetter, 2008).

As the incidence of diabetes mellitus, obesity, and high BP continues to rise, it is estimated that by the year 2015, there will be 136,000 new individuals per year with end stage CKD and 712,000 individuals with CKD in the U.S. (Gilbertson et al., 2007). These overwhelming statistics increase the salience of modifiable risk factors as a basis for developing treatment strategies for preventing the development and progression of CKD (Haroun et al., 2003). While cardiovascular disease and diabetes mellitus are the clinical outcomes of primary consequence from metabolic syndrome, CKD risk is also of concern (Grundy, Brewer, Cleeman, Smith, & Lenfant, 2004). Hypertension, glucose intolerance, elevated BMI, and dyslipidemia are factors that are part of metabolic syndrome, and these factors increase the risk for development of CKD. Although cigarette smoking is not a component of metabolic syndrome, it is also a known modifiable risk factor that contributes to the development of cardiovascular disease, cancers, CKD, and other chronic diseases, and is the leading cause of preventable death in the U.S. (Danaei et al., 2009). Interventions that delay and prevent the onset of diabetes mellitus, reduce obesity, support smoking cessation, and control hypertension and dyslipidemia should be considered to improve mortality, morbidity, and disability, and specifically, to prevent or delay CKD. The purposes of this study were to examine the presence of modifiable CKD risk factors in African Americans with metabolic syndrome who have no known history of CKD and to compare the presence of modifiable risk factors by gender.

Review of the Literature

Metabolic Syndrome and CKD

Metabolic syndrome is a group of risk factors that coexist and increase an individual's risk for diabetes mellitus and cardiovascular disease. Based on data from NHANES III, it is estimated that 47 million American adults 20 years of age and older have metabolic syndrome (Chen et al., 2004; Ford, Giles, & Dietz, 2002). The National Cholesterol Education Program's [NCEP] Adult Treatment Panel III defines metabolic syndrome as the presence of three of the following five criteria: abdominal obesity as defined by waist circumference of 102 cm in men and greater than 88 cm in women, triglycerides of 150 mg/dL or higher, high density lipoprotein (HDL) less than 40 mg/dL in men and less than 50 mg/dL in women, BP of 130/85 mmHg or higher, and fasting glucose of greater than 100 mg/dL (NCEP, National Heart, Lung, and Blood Institute [NHLBI], & National Institutes of Health [NIH], 2002). The prevalence of metabolic syndrome using NCEP criteria is similar for both men and women; however, African-American women have a higher prevalence of metabolic syndrome when compared to African-American men (Ford et al., 2002).

The Kidney Disease Outcomes Quality Initiative (KDOQI) defines CKD as either kidney damage or glomerular filtration rate less than 60 ml/min/1.73m2 for three months or longer (NKF, 2002). The degree of kidney function correlates with five stages of disease severity, from CKD with a normal glomerular filtration rate of 90 ml/min/1.73m2 or higher, to CKD Stage 5 with glomerular filtration rate less than 15 ml/min/1.73m2. Using the definition of metabolic syndrome as described by the NCEP criteria and the classification of CKD as stated by KDOQI, data from participants in NHANES III were analyzed to determine the association between the metabolic syndrome and CKD (Chen et al., 2004). The results of the study showed that the odds ratio for CKD in participants with metabolic syndrome was 2.60 as compared to an odds ratio of 1.89 for participants without metabolic syndrome. In a prospective study that examined the relationship between metabolic syndrome and CKD, Kurella et al. (2005) demonstrated that metabolic syndrome is independently associated with the development CKD. The risk for CKD increased with each additional metabolic syndrome component. This relationship remained consistent even after controlling for age, gender, and race.

Diabetes Mellitus as a CKD Risk Factor in Metabolic Syndrome

Type II diabetes mellitus is the leading cause of CKD in the U.S. (USRDS, 2009). It is estimated that 17.9 million Americans have diagnosed diabetes, and an additional 5.7 million Americans have undiagnosed diabetes (Centers for Disease Control and Prevention [CDC], 2007). Thirty percent (30%) of the U.S. population has impaired fasting glucose – a precursor to diabetes (Cowie et al., 2009). Serum glucose levels that do not meet diabetes criteria but are too high to be considered normal are classified as impaired fasting plasma glucose (100 to 125 mg/dL) or impaired oral glucose tolerance (140 to 199 mg/dL). Individuals with impaired fasting glucose have a relatively high risk for developing type II diabetes mellitus (United Kingdom Prospective Diabetes Study [UKPDS] Group, 1998). Impaired fasting glucose is more common in men (70%) than in women, and minority ethnic groups have the highest prevalence of diagnosed diabetes (Cowie et al., 2009).

Type II diabetes mellitus is characterized by high glucose levels as a result of insulin resistance and insulin deficiency (McCance & Huether, 1994). This hyperinsulinemia state has been demonstrated in patients with no clinical history of diabetes. A significant positive correlation between insulin resistance and concomitant hyperinsulinemia was reported in patients who had CKD with no clinical signs of diabetes (Chen et al., 2003). In individuals with a history of type II diabetes mellitus, there is evidence that persistent blood sugar control reduces the development of kidney disease (UKPDS Group, 1998).

Hypertension as a CKD Risk Factor in Metabolic Syndrome

Hypertension is the second leading cause of CKD and one of the factor components of the metabolic syndrome (Coresh et al., 2001). Prevalence of high BP in African-American men is 35% and 34.2% in African-American women, as compared to 24.4% in non-Hispanic White men and 19.3% in non-Hispanic White women (Burt et al., 1995). The Seventh Report of the Joint National Committee [JNC-7] on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (Chobanian et al., 2003) emphasizes that the primary public health outcome of antihypertensive therapy is reduction of cardiovascular and renal morbidity and mortality. JNC-7 established a BP goal of less than 130/80 for adults with CKD or diabetes. Only 27% of those treated for high BP are at goal; this percentage is even lower in African Americans (Chobanian et al., 2003). Overall, hypertension awareness has not changed in the past decade, and intervention rates have only marginally increased by less than 10% (Kottke, Stroebel, & Hoffman, 2003).

Angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are recommended as the first line of anti-hypertensive therapy for individuals with hypertensive CKD (Appel et al., 2008; Chobanian et al., 2003). Data on the effectiveness of ACE inhibitors or ARB over other BP medications in individuals at risk for CKD are inconclusive. In a large study (n = 1094) that compared ACE inhibitors to calcium channel blockers and beta blockers, in African Americans with hypertensive CKD, 52% of the participants experienced poor outcomes, including a doubling of the serum creatinine level from trial baseline, developing Stage 5 CKD, or death (Appel et al., 2008). Using data from the Antihypertensive Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) cohort, the clinical outcomes by race for hypertensive participants with and without metabolic syndrome were compared (Wright et al., 2008). Calcium channel blockers, ACE inhibitors, and alpha blockers were not superior to the thiazide diuretics in hypertension management for African Americans. African Americans whose high BP is managed with monotherapy experience an increased prevalence and severity of hypertension because of a reduced response to single drug therapy. These differences are largely eliminated using adequate diuretics with other antihypertensive medications (Chobanian et al., 2003; Wright et al., 2008).

Hyperlipidemia as a CKD Risk Factor in Metabolic Syndrome

Lipid abnormalities are commonly associated with cardiovascular risk in CKD, but recently, evidence has emerged that dyslipidemia is a risk factor for the incidence and progression of CKD (Taal & Brenner, 2006). The Modification of Diet in Renal Disease (MDRD) study (Hunsicker et al., 1997), a multicenter randomized clinical trial that evaluated the effectiveness of dietary protein restriction and tight BP control on the progression of renal disease in 840 patients with various stages and etiologies of CKD, identified low blood HDL cholesterol as an independent predictor of decline in renal function. A meta-analysis of 13 randomized controlled trials that explored the effects of lipid-lowering medication on the progression of kidney disease reported a decreased rate of decline in glomerular filtration for the treatment groups (Fried, Orchard, & Kasiske, 2001). In a community longitudinal cohort study involving 2585 participants from the Framingham Offspring study, HDL cholesterol was a baseline predictor of developing kidney disease after adjusting for age and gender (Fox et al., 2004). Lipid abnormalities have been associated with the onset and progression of kidney disease; however, the most predictive lipid variable has not been clearly defined (Dalrymple & Kaysen, 2008).

Obesity as a CKD Risk Factor In Metabolic Syndrome

Individuals with a BMI of 25 to 29.9 are considered overweight, and individuals with a BMI of 30 or greater are considered obese. All overweight and obese adults with a BMI greater than 25 are considered at risk for developing associated morbidities or chronic diseases (NHLBI & the National Institute of Diabetes and digestive and Kidney Diseases [NIDDK], 1998). Excessive waist circumference is recognized as a form of abdominal obesity (Grundy et al., 2004). Abdominal obesity is related to a two-fold increase in odds for CKD (Chen et al., 2004). In the Framingham Offspring study, Fox et al. (2004) elevated BMI increased the odds of developing CKD by 23% per standard deviation unit. The result of an analysis of NHANES I, II, and III on trends of obesity in the U.S. showed a sharp increase (5.8%) in obesity in the U.S. between NHANES II and NHANES III (Flegal, Carroll, Kuczmarski, & Johnson, 1998). Overweight and obesity disproportionately affect more women than men (Danaei et al., 2009). According to NHANES III data, African-American women have the highest rate of abdominal obesity when compared to other ethnic groups in the U.S. (Flegal et al., 1998; Williams, Flack, Gavin, Schneider, & Hennekens, 2007).

Smoking as a CKD Risk Factor in Metabolic Syndrome

Cigarette smoking is not recognized as a component of the metabolic syndrome; however, it is identified as a risk factor for CKD, cardiovascular disease, lung cancer, stroke, and other chronic illnesses. According to the 2008 National Health Interview Survey, more men (23.1%) smoke than compared to women (18.3%), and 21.3% of African Americans smoke (CDC, 2009). In a population-based study of older adults, smoking was associated with CKD independent of BMI, high BP, diabetes, alcohol in-take, and other confounders (Shankar, Klein, & Klein, 2006). The odds ratio of developing CKD was 1.12 among previous smokers and 1.97 among current smokers. In a prospective study of CKD risk factors, smoking was found to have an attributable risk of 31% or 3460 per million population (Haroun et al., 2003). The study showed that current smoking was associated with a 2.5 times greater risk of later development of CKD.

Dietary Modification in Management of CKD Risk Factors in Metabolic Syndrome

Dietary lifestyle modifications and adoption of healthy lifestyle choices by all individuals are paramount in reducing the risk associated with metabolic syndrome and CKD. Nutritional intervention to reduce health consequences associated with metabolic syndrome is an essential part of management for those individuals with hypertension (Chobanian et al., 2003). The Dietary Approaches to Stop Hypertension (DASH) trials demonstrate the impact of dietary patterns on BP rates.

Diet rich in fruits, vegetables, and foods low in dairy fat, sodium, and saturated and total fats lowered systolic and diastolic pressure in hypertensive patients by 11.4 to 5.5 mmHg (Appel et al., 1997). BP reduction gained from nutritional approaches to preventing hypertension is similar in magnitude to that observed in trials using drug monotherapy for treating mild hypertension (Appel et al., 1997).

Summary

Although incident rates of CKD in African Americans are not gravely different from rates in other ethnic groups, racial health disparities in progression to Stage 5 CKD in African Americans remain significant.

Multiple clinical and lifestyle factors, when left unrecognized or inadequately managed, may result in irreversible permanent kidney damage. Diabetes, hypertension, dyslipidemia, cigarette smoking, overweight/obesity, physical inactivity, and dietary patterns have all been identified as modifiable risk factors (American Diabetes Association, 2009; Chobanian et al., 2003; NCEP, NHLBI, & NIH, 2002; NKF, 2002; Williams et al., 2007). Variables that are components of these lifestyle and clinical risk sets represent important intervention targets (McClellan & Flanders, 2003).

Methodology

Design

A descriptive comparative design was used to examine modifiable risk factors for CKD in men and women with metabolic syndrome (N = 104). The study used baseline data collected as part of a larger study, the Morehouse and Emory are Teaming up to eliminAte Health Disparities Cohort (META-Health) (U.S. Department of Health and Human Services [DHHS], NIH, & NHLBI, 2004). META-Health is a collaborative study with multiple aims designed to investigate racial disparities in African Americans with metabolic syndrome at risk for cardiovascular events in a larger southeastern urban community. The data for this study were drawn from the baseline data of a lifestyle intervention study, which was one of the aims of META-Health.

Sample

After obtaining Institutional Review Board (IRB) approval, participants were recruited from the local community using flyers and a community primary care practice database. Eligibility criteria included African American; 18 years of age or older; a diagnosis of hypertension and at least two other NCEP criteria for metabolic syndrome; no known history of CAD, CKD, or diabetes mellitus; considered to have sedentary lifestyles; and could read and speak English. Study coordinators screened individuals for inclusion criteria and consented participants accordingly.

Setting/Procedure

Participants' baseline data were collected during face-to-face interviews at a local clinical research center. Self-report information on participants' education level, income, activity level, dietary consumption, family health history, and medical history were obtained. Objective data on participants' weight, height, waist circumference, and BP were obtained by trained study coordinators. Blood samples were obtained for fasting glucose, creatinine, and additional biomarkers to be analyzed at a later date according to study protocol. Participants were subsequently randomized to intervention or usual care and followed over a 12-month period. Participants received a $25 gift card following each phase of data collection at the Clinical Research Center. Only baseline data prior to randomization were reported.

Instruments

Weight was measured in kilograms using a calibrated scale, and height was measured in centimeters using a standard stadiometer. Obesity was measured using BMI. BMI was calculated as weight (kilograms) divided by height (centimeters) squared (NCEP, NHLBI, & NIH, 2002). BP was measured at rest in the seated position using an automated BP machine. If the BP was 130/80 or higher, the reading was validated using a manual sphygmomanometer. Both plasma glucose and serum creatinine levels were obtained through standard laboratory protocols and analyzed using standard laboratory method (Myers et al., 2006).

Data Analysis

All data were analyzed using SAS version 9.1 statistical analysis program. Descriptive statistics were used to analyze demographic and clinical data. Inferential statistics were used to compare data by gender. Chi-square or Fisher-exact tests were conducted to examine relationships between categorical variables. Mean differences between men and women on continuous variables were analyzed using Wilcoxon Signed- Rank test. Alpha was established as p < 0.05 as criterion for statistical significance, using two-tailed tests.

Results

Baseline data were analyzed for 104 participants. There were 80 women (77%) and 24 men (23%). Table 1 summarizes demographic and clinical variables by gender. Participants were primarily middle age and college educated. More than half of men were married, but less than half of women were married. About half of the participants had systolic and diastolic BPs at a range higher than recommended. This reflects a large number who had BPs considered to be in the hypertensive or uncontrolled range. One possibility that should be noted is that participants had to be fasting for the visit to the center and took regular BP medications after their blood sample was drawn. This may have affected the BP ranges of some of the participants; however, missing one dose is unlikely to affect such a large percentage. Therefore, there is continued concern about the lack of BP control in this hypertensive sample. Elevated fasting serum glucose (100 to 125 mg/dL) was noted in 25% of participants, although participants had no known history of diabetes. Elevated lipoproteins, a positive smoking history, and obesity were CKD risk factors present in this cohort. Although there was no significant difference between genders in smoking history, obesity or dyslipidemia, on average, women had HDL levels at the low end of the acceptable range of less than 50 mg/dL, while men on average were slightly above the 40 mg/dL, considered acceptable for men.

Table 1. Demographic and Clinical Variables for Total Sample and by Gender.

Gender Total Sample
N = 104
Men n = 24 Women n = 80
Age (years) – (M ± SD) 50.6 ± 7.5 49.3 ± 9.0 49.6 ± 8.65
Married – n (%) 14 (58.3) 31 (40.3) 45 (44.6)
College – n (%)
 Yes 18 (75.0) 57 (74.0) 75 (74.3)
 No 6 (25.0) 20 (26.0) 26 (25.8)
Income less than $19,000/year – n (%)
 Yes 3 (12.5) 6 (7.6) 9 (8.8)
 No 21 (87.5) 73 (92.4) 94 (91.3)
Smoking – n (%)
 Never 14 (58.3) 56 (70.0) 70 (67.3)
 Current 3 (12.5) 5 (6.3) 8 (7.7)
 Former 7 (29.2) 19 (23.8) 26 (25.0)
BP less than 130/80 – n (%)
 Yes 9 (41.0) 37 (50) 46 (47.9)
 No 13 (59.0) 37 (50) 50 (52.1)
Fasting glucose – n (%)
 Less than 100 mg/dL 17 (70.8) 53 (71.7) 70 (71.4)
 100 to 125 mg/dL 6 (25.0) 19 (25.7) 25 (25.5)
 126 mg/dL or higher 1 (4.2) 2 (2.7) 3 (3.06)
BMI – n (%)
 Less than 25 0 1 (1.4) 1 (1.4)
 25 to 29.9 3 (12.5) 6 (8.1) 9 (9.2)
 30 or higher 21 (87.6) 67 (90.5) 88 (89.8)
HDL – (M ± SD)
 mg/dL 47 ± 12.8 50.5 ± 11.8 49.6 ± 11.9
LDL – (M ± SD)
 mg/dL 109.2 ± 29.8 117.8 ± 34.6 116.2 ± 34.3
Serum creatinine – (M ± SD)*
 mg/dL 1.16 ± 0.17 0.86 ± 0.17 0.93 ± 0.21
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Note: BP = blood pressure; BMI = body mass index.

*

p < 0.0001 comparing men and women.

A series of Wilcoxon Signed-Rank tests were conducted to examine gender differences on continuous variables. Results indicated that serum creatinine values in men (1.16 mg/dL), when compared to women (0.86 mg/dL), were significantly higher (Z = 5.9717, p < 0.0001). No differences were found across groups regarding mean systolic BP (Z = 0.6586, p > 0.05), mean fasting glucose levels (Z = 0.0041, p > 0.05), BMI (Z = -0.5958. p > 0.05), or age (Z = 0.5115, p > 0.05).

Participants reported being prescribed a variety of hypertension medications (see Table 2). Approximately 44.3% were receiving monotherapy, which was primarily in the form of diuretics. There was no difference by gender in BP measures being controlled to JNC-7 target of less than 130/80 (χ2 [1, n = 96] = 0.562, p > 0.05). No gender differences were found in rates of ACE inhibitor or ARB use (χ2 [1, n = 63] = 2.80, p > 0.05). Similarly, there was no gender difference in smoking history (χ2 [2, n = 104] = 1.53, p > 0.05). There was no difference between men and women with regards to being prescribed a diuretic, beta-blocker, or calcium channel blocker (Fisher's exact, p > 0.05). Less than half of the participants were on combination therapy to manage their BP.

Table 2. Antihypertension Medications.

Number of Agents – n (%) Gender Total
Men Women
 Monotherapy 11 (61.1) 24 (39.3) 35 (44.3)
 Dual therapy 5 (27.8) 32 (52.5) 37 (46.8)
 Triple therapy 1 (5.6) 3 (4.9) 4 (5.1)
Medication classification
ACE/ARB – n (%)
 Yes 12 (75.0) 24 (51.1) 36 (57.1)
 No 4 (25.0) 23 (49.0) 27 (42.9)
Diuretic – n (%)
 Yes 8 (57.1) 44 (78.6) 52 (74.3)
 No 6 (42.9) 12 (21.4) 18 (25.7)
Beta Blocker – n (%)
 Yes 2 (16.7) 14 (31.8) 16 (28.6)
 No 10 (83.3) 30 (68.2) 40 (71.4)
Calcium Channel Blocker – n (%)
 Yes 3 (25.0) 16 (32.0) 19 (30.7)
 No 9 (75.0) 34 (68.0) 43 (69.4)
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Discussion

Summary

Results of this study suggest that both African-American men and women with metabolic syndrome are at increased risk for CKD because of elevated fasting serum glucose levels and the presence of obesity. In this African-American metabolic syndrome cohort, participants had no known history of CKD, 28.6% had fasting glucose levels of 100 mg/dL or higher, and 99% had BMI measurements greater than 25, all of which are CKD antecedents. These findings are similar to the results of an analysis of the NKF's Kidney Early Evaluation and Detection Program (KEEP), a CKD community-based detection and prevention program (Vassalotti et al., 2006). In general, 44.8% of KEEP participants were African American, 50% of all participants had abnormally high glucose levels, and African Americans and older adults (91%) were more likely to have BP measures greater than 130/80. Unlike non-modifiable CKD risk factors, such as race and family history of CKD, BP, diabetes, BMI, and smoking, are all modifiable CKD risk factors (Tarver-Carr et al, 2002; Williams et al., 2007).

When compared by gender, serum creatinine was significantly higher in men than women. However, serum creatinine is limited in the diagnosis of true kidney function because of variation among laboratories in assays and because its level is also affected by physiologic processes other than glomerular filtration rate, including generation (very dependent on muscle mass and protein intake), proximal tubular secretion, and extrarenal elimination (NKF, 2002). NKF recommends using estimation equations (such as MDRD) that incorporate creatinine in association with age, sex, and race to estimate glomerular filtration rate and stage CKD.

Lifestyle modifications have been recommended as a primary weapon in the healthcare arsenal to prevent CKD. Increasing physical activity; reducing sodium consumption; maintaining a healthy weight; and eating a diet high in fiber, fruits, and vegetables; low in fat dairy product; and reduced fats and cholesterol have been recommended to lower BP, reduce BMI, and decrease the risk for diabetes (Appel et al., 1997; Martinson, O'Connor, & Pronk, 2001). In this current study, a BMI greater than 25 was the most prevalent modifiable risk factor in both men and women. The Atherosclerosis Risk Communities Cohort Longitudinal Study followed over 15,000 individuals without diabetes and with metabolic syndrome, and measured their risk for end stage CKD (Kurella et al., 2005). African Americans in the study had a higher incidence of abdominal obesity, hypertension, and hyperglycemia when compared to Whites. Obesity may be the primary modifiable CKD risk factor that has the greatest potential to positively impact diabetes and hypertension, the two leading causes of CKD.

Prevalence of uncontrolled hypertension among African Americans remains significantly high, and the high use of monotherapy in this population is of concern. The uniqueness of BP control in African Americans is recognized by the JNC-7; therefore, combination therapy that includes diuretic with an ACE inhibitor/ARB is the pharmacology intervention of choice (Chobanian et al., 2003). Even with combination therapy, lifestyle modification through diet and exercise remain an essential element in BP control. Healthcare providers must be vigilant in timely management of out-of-target range BP measurements in African Americans. Poorly controlled BP in African Americans accounts for nearly 8,000 excess deaths per year from cardiovascular events (Fiscella & Holt, 2008). BP readings in this known hypertensive group were high, with the delayed dose of morning medications indicating the importance of maintaining daily medication adherence for BP control.

Much of the health disparity in CKD has been linked to access to care with the thought that universal access to care could eliminate a large percentage of CKD-related racial and ethnic disparities. Outcomes from a study that examined quality of care for more than 8,000 patients with CKD treated in the Department of Defense (DoD) medical system suggested that care provided to African-American patients with CKD in the DoD system was equivalent to that provided to White patients (Gao et al., 2008). In addition, CKD education directed toward healthcare providers is also needed. A study conducted by the National Kidney Disease Education Program [NKDEP] (Lea, McClellan, Melcher, Gladstone, & Hostetter, 2006) explored the awareness of CKD risk factor and treatment practices of 465 primary care physicians. The study concluded that most providers (65%) diagnosed CKD at a creatinine level within a diagnosis range preferred by NKDEP, about 75% gave a suitable albumin/creatinine ratio diagnosis end point, only 35% gave a satisfactory proteinuria diagnosis point, and only 20% provided a plausible estimated glomerular filtration rate diagnosis end point. Awareness of CKD risk factors was only marginal because about one-third of physicians did not recognize family history of CKD as a non-modifiable CKD risk factor, and one-fifth did not view African-American race as a CKD risk factor.

Study Limitations

This study had several limitations. The cross-sectional design of this study provided a limited view of the individual's risk factors over time. Comparing data over time would provide a better analysis of clinical factors and participant management of risk factors. This study did not examine baseline microalbumin levels, which are considered the strongest predictor of CKD progression (NKF, 2002; Norris et al., 2006); however, the larger collaborative study did assess microalbumin. The results cannot be generalized to other ethnic groups because the cohort included only African Americans. The number of men was much smaller than the number of women and may limit study generalizability as well.

Nursing Implications

Metabolic syndrome is an independent risk factor for CKD. Two components of metabolic syndrome, elevated serum fasting glucose (diabetes precursor) and hypertension, are the primary contributors to the incidence of CKD, and they were highly prevalent in this sample residing in a southern urban environment. Early detection and appropriate management of modifiable CKD risk factors are necessary for the prevention or delay of CKD onset. This is extremely important for African Americans, who are disproportionately affected by CKD, may experience a greater burden of metabolic syndrome components, and who tend to progress more rapidly to end stage CKD than any other ethnic group. Assisting African Americans in navigating the health behavior practices required in CKD prevention may help to greatly reduce the racial disparity of CKD for African Americans.

As core members of the healthcare team, nephrology nurses are in a unique position to educate patients and other healthcare providers about modifiable CKD risk factors. Nephrology nurses possess extensive knowledge of CKD prevention strategies and are the ideal healthcare professionals to assist individuals with adopting healthy lifestyle practices, with a focus on weight reduction and increasing physical activity. Nephrology nurses traditionally may not interface with an individual until the diagnosis of CKD. The challenge is for nephrology nurses to take an active role earlier in the disease prevention continuum in the domain of CKD management. Nephrology nurses should consider leading disease education and prevention initiatives that include screening high-risk groups for CKD risk factors and focusing on controlling BPs using national guidelines. Medication management to treat components of metabolic syndrome is only effective in the realm of patient self-management. Nephrology nurse-led CKD prevention initiatives that support African Americans in adopting and maintaining health protective behaviors is the synergistic element that can enhance the medication management model and lead to long-lasting lifestyle practices for African Americans.

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Nephrology Nursing Journal Editorial Board Statements of Disclosure.

In accordance with ANCC-COA governing rules Nephrology Nursing Journal Editorial Board statements of disclosure are published with each CNE offering. The statements of disclosure for this offering are published below.

Paula Dutka, MSN, RN, CNN, disclosed that she is a consultant for Hoffman-La Roche and Coordinator of Clinical Trials for Roche.

Patricia B. McCarley, MSN, RN, NP, disclosed that she is on the Consultant Presenter Bureau for Amgen, Genzyme, and OrthoBiotech. She is also on the Advisory Board for Amgen, Genzyme, and Roche and is the recipient of unrestricted educational grants from OrthoBiotech and Roche.

Holly Fadness McFarland, MSN, RN, CNN, disclosed that she is an employee of DaVita, Inc.

Karen C. Robbins, MS, RN, CNN, disclosed that she is on the Speakers' Bureau for Watson Pharma, Inc.

Acknowledgments

This work was partially supported by funding from the National Heart, Lung, and Blood Institute, NIH (1U01 HL079156-01) and PHS Grant M01-RR00039, NIH, National Center for Research Resources (NCRR), Emory General Clinical Research Center, and Grant Number 5P20RR11104 from the NIH National Center for Research Resources (NCRR), Morehouse School of Medicine, Clinical Research Center. “The contents are solely the responsibility of the authors and do not necessarily represent the official views of NCRR or NIH.”

Footnotes

Goal: To provide an overview of modifiable risk factors for CKD in African Americans of both genders with metabolic syndrome.

Objectives

  1. Explain metabolic syndrome as it relates to CKD.
  2. Describe the CKD risk factors in metabolic syndrome.
  3. Outline this current study's method and results.

Statement of Disclosure: The authors reported no actual or potential conflict of interest in relation to this continuing nursing education article.

Contributor Information

Loretta Jackson Brown, Email: lorettajbrown@bell-south.net, Doctoral Nursing Student, Byrdine F. Lewis School of Nursing, Georgia State University, Atlanta, GA, and is a member of ANNA's Dogwood Chapter.

Patricia C. Clark, Professor, Byrdine F. Lewis School of Nursing, Georgia State University, Atlanta, GA.

Karen A. Armstrong, Former Research Coordinator, Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA.

Zhao Liping, Senior Biostatistician, Emory Program in Cardiovascular Outcomes Research and Epidemiology, Atlanta, GA.

Sandra B. Dunbar, Charles Howard Candler Professor of Cardiovascular Nursing, Department of Adult and Elder Health Nursing, Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA.

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