American Indian heritage and risk factors for renal injury

Socioeconomic disparities in chronic kidney disease: a systematic review and meta-analysis

CONTEXT

Evidence on the strength of the association between low SES and chronic kidney disease (CKD; measured by low estimated glomerular filtration rate [eGFR], high albuminuria, low eGFR/high albuminuria, and renal failure) is scattered and sometimes conflicting. Therefore, a systematic review and meta-analysis was performed to summarize the strength of the associations between SES and CKD and identify study-level characteristics related to this association.

EVIDENCE ACQUISITION

Studies published through January 2013 in MEDLINE and Embase were searched. From 35 studies that met the inclusion criteria, association estimates were pooled per CKD measure in the meta-analysis (performed between 2013 and 2014). Meta-regression analysis was used to identify study-level characteristics related to the strength of the SES-CKD association.

EVIDENCE SYNTHESIS

Low SES was associated with low eGFR (OR=1.41, 95% CI=1.21, 1.62), high albuminuria (OR=1.52, 95% CI=1.22, 1.82), low eGFR/high albuminuria (OR=1.38, 95% CI=1.03, 1.74), and renal failure (OR=1.55, 95% CI=1.40, 1.71). Differences in SES measures across studies were not related to the strength of associations between low SES and any of the CKD measures (low GFR, p=0.63; high albuminuria, p=0.29; low eGFR/high albuminuria, p=0.54; renal failure, p=0.31). Variations in the strength of associations were related to the level of covariate adjustment for low eGFR (p<0.001) and high albuminuria (p<0.001).

CONCLUSIONS

Socioeconomic disparities in CKD were fairly strong, irrespective of how SES was measured. Variations in the strength of the associations were related to the level of covariate adjustment, particularly for low eGFR and high albuminuria.

Chronic kidney disease in disadvantaged populations

The increased burden of chronic kidney disease (CKD) in disadvantaged populations is due to both global factors and population-specific issues. Low socioeconomic status and poor access to care contribute to health care disparities and exacerbate the negative effects of genetic or biological predisposition. Provision of appropriate renal care to these populations requires a two-pronged approach: expanding the reach of dialysis through development of low-cost alternatives that can be practiced in remote locations, and implementation and evaluation of cost-effective prevention strategies. Kidney transplantation should be promoted by expansion of deceased donor transplant programs and use of inexpensive, generic immunosuppressive drugs. The message of World Kidney Day 2015 is that a concerted attack against the diseases that lead to end-stage renal disease, by increasing community outreach, better education, improved economic opportunity, and access to preventive medicine for those at highest risk, could end the unacceptable relationship between CKD and disadvantage in these communities.

Chronic kidney disease in disadvantaged populations

The increased burden of CKD in disadvantaged populations is due to both global factors and population-specific issues. Low socioeconomic status and poor access to care contribute to healthcare disparities and exacerbate the negative effects of genetic or biologic predisposition. Provision of appropriate renal care to these populations requires a two-pronged approach: expanding the reach of dialysis through development of low-cost alternatives that can be practiced in remote locations, and implementation and evaluation of cost-effective prevention strategies. Kidney transplantation should be promoted by expanding both deceased donor transplant programs and the use of inexpensive, generic immunosuppressive drugs. The message of WKD 2015 is that a concerted attack against the diseases that lead to ESRD, by increasing community outreach, better education, improved economic opportunity, and access to preventive medicine for those at highest risk, could end the unacceptable relationship between CKD and disadvantage in these communities.

Chronic kidney disease (CKD) in disadvantaged populations

Twelve March 2015 will mark the 10th anniversary of World Kidney Day (WKD), an initiative of the International Society of Nephrology and the International Federation of Kidney Foundations. Since its inception in 2006, WKD has become the most successful effort ever mounted to raise awareness among decision-makers and the general public about the importance of kidney disease. Each year WKD reminds us that kidney disease is common, harmful and treatable. The focus of WKD 2015 is on chronic kidney disease (CKD) in disadvantaged populations. This article reviews the key links between poverty and CKD and the consequent implications for the prevention of kidney disease and the care of kidney patients in these populations.

The impact of disadvantage on the development and progression of diabetic kidney disease

BACKGROUND

Disadvantaged people include those experiencing economic, social or educational deprivation and, in some cases, those undergoing rapid transition from subsistence to industrial economies. Disadvantaged people worldwide are affected disproportionately by the global epidemic of diabetes. They are also at increased risk of kidney disease attributable to diabetes, and for many, the cost of managing their kidney disease far exceeds their available resources.

METHODS

We review factors associated with disadvantage that may increase the risk of diabetic kidney disease, and the barriers to care that hinder attempts to provide an adequate therapeutic response.

RESULTS AND CONCLUSIONS

A rapidly rising prevalence and magnitude of obesity among children and adults, increasing frequency of intrauterine exposure to diabetes, and inadequate access to healthcare are responsible, in part, for a surge in the frequency of diabetes and, in turn, diabetic kidney disease among disadvantaged people. These factors may also predispose to an earlier onset of diabetes and kidney disease, thereby perpetuating the disadvantage by reducing the earning potential of those affected through illness and disability.

Albuminuria among Alaska Natives--findings from the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study

BACKGROUND

The prevalence and associated risk factors for albuminuria and low-grade albuminuria in Alaska Natives is not known.

METHODS

Cross-sectional analysis of the Genetics of Coronary Artery Disease in Alaska Natives Study. We included 1,026 individuals, who represent 85% of the study participants for whom complete data were available. Risk factors examined were age, sex, education, diabetes, hypertension, obesity, lipids, C-reactive protein, angiotensin-converting enzyme inhibitor use, and smoking status. Urine albumin excretion was estimated by the albumin/creatinine ratio measured from a single random morning urine sample. Albuminuria was defined as an albumin/creatinine ratio of > or =30 mg/g. Low-grade albuminuria was defined as an albumin/creatinine ratio of 10 to <30 mg/g.

RESULTS

The mean age was 42 years and over half were female. Diabetes prevalence was low at 3% and the prevalence of hypertension was 20%. The prevalence of albuminuria was 6%; the prevalence of low-grade albuminuria was 12%. Individuals with diabetes or hypertension were 3 times more likely to have albuminuria than those without these conditions [odd ratios: diabetes 3.0 (1.2-7.9) and hypertension 3.0 (1.2-7.3)].

CONCLUSIONS

The burden of albuminuria is low. Comprehensive programs and policies are important given the rise in diabetes and hypertension among Alaska Natives.

Racial and ethnic differences in albuminuria in individuals with estimated GFR greater than 60 mL/min/1.73 m(2): results from the Kidney Early Evaluation Program (KEEP)

BACKGROUND

Albuminuria is an important marker for chronic kidney disease and progression to end-stage renal disease in the general population; understanding racial and ethnic differences can help inform efforts to reduce health disparities. We sought to estimate independent associations of race/ethnicity with albuminuria to determine whether observed differences were attributable to known kidney disease risk factors.

METHODS

This cross-sectional study included 64,161 Kidney Early Evaluation Program (KEEP) participants, 2000-2008, with estimated glomerular filtration rate > or = 60 mL/min/1.73 m(2), not on regular dialysis therapy, and without a previous kidney transplant. Albuminuria (urine albumin-creatinine ratio > or = 30 mg/g) was examined by self-reported race and ethnicity. Covariates were age, sex, educational level, body mass index, diabetes status or glucose level, hypertension status or blood pressure measurement, smoking status, health insurance status, and geographic region.

RESULTS

Albuminuria prevalences were 8% (n = 2,303) in whites, 11% (n = 2,310) in African Americans, 9% (n = 730) in Hispanics, 10% (n = 381) in Asians, and 15% (n = 344) in American Indians/Alaska Natives. Compared with whites, odds of albuminuria were higher for all groups after multivariate adjustment. Odds were highest for American Indians/Alaska Natives (adjusted OR, 1.93; 95% CI, 1.70-2.20), then Asians (adjusted OR, 1.42; 95% CI, 1.26-1.61), African Americans (adjusted OR, 1.38; 95% CI, 1.29-1.47), and Hispanics (adjusted OR, 1.19; 95% CI, 1.08-1.31).

CONCLUSIONS

In the KEEP study population, albuminuria prevalence was higher in African Americans, Hispanics, Asians, and American Indians/Alaska Natives than in non-Hispanic whites, suggesting a need for screening for early detection of kidney damage, especially in people at increased risk, in the community primary care setting.

Linkage analysis of albuminuria

American Indians have a higher prevalence of albuminuria than the general population, likely resulting from a combination of environmental and genetic risk factors. To localize gene regions influencing variation in urinary albumin-to-creatinine ratio, we performed a linkage analysis and explored gene-by-diabetes, -hypertension, and -obesity interactions in a large cohort of American Indian families. We recruited >3600 individuals from 13 American Indian tribes from three centers (Arizona, North and South Dakota, and Oklahoma). We performed multipoint variance component linkage analysis in each center as well as in the entire cohort after controlling for center effects. We used two modeling strategies: Model 1 incorporated age, gender, and interaction terms; model 2 also controlled for diabetes, BP, body mass index, HDL, LDL, triglycerides, and smoking status. We evaluated interactions with diabetes, hypertension, and obesity using additive, interaction-specific linkage and stratified analyses. Loci suggestive for linkage to urinary albumin-to-creatinine ratio included 1q, 6p, 9q, 18q, and 20p. Gene-by-diabetes interaction was present with a quantitative trait locus specific to the diabetic stratum in the Dakotas isolated on 18q21.2 to 21.3 using model 1 (logarithm of odds = 3.3). Gene-by-hypertension interaction was present with quantitative trait loci specific to the hypertensive stratum in the Dakotas on 7q21.11 using model 1 (logarithm of odds = 3.4) and 10q25.1 using model 2 (logarithm of odds = 3.3). These loci replicate findings from multiple other genome scans of kidney disease phenotypes with distinct populations and are worthy of further study.

Risk factors for chronic kidney disease among American Indians and Alaska Natives--findings from the Kidney Early Evaluation Program

BACKGROUND

American Indians and Alaska Natives (AIAN) have a high incidence of end-stage renal disease. Less is known about chronic kidney disease (CKD) among AIAN and whether risk factors differ for low estimated glomerular filtration rate (eGFR) versus albuminuria with a normal eGFR.

METHODS

Cross-sectional study examining the associations of age, sex, smoking, obesity, diabetes, hypertension, family history, and geographic region with CKD among a screened population of AIAN participants in the Kidney Early Evaluation Program from 2000 to 2006. CKD was defined by the presence of either a low eGFR, <60 ml/min/1.73 m(2), or albuminuria, a urine albumin/creatinine ratio > or =30 mg/g.

RESULTS

The prevalence of any CKD was 29%, of low eGFR was 17%, and of albuminuria with a normal eGFR was 12%. Older age was the strongest predictor of low eGFR (61+ years OR 8.42, 95% CI 5.92-11.98), followed by hypertension (OR 2.38, 95% CI 1.74-3.26). In contrast, diabetes (OR 2.04, 95% CI 1.57-2.64) and hypertension (OR 2.63, 95% CI 1.93-3.59) were the only predictors of albuminuria among persons with a normal eGFR.

CONCLUSION

The burden of CKD was high among this screened population of AIAN, and different risk factor patterns were associated with low eGFR and albuminuria. Innovative programs and longitudinal research are needed to address CKD among AIAN.

Prevalence of chronic kidney disease and survival among aboriginal people

Globally, it is known that the incidence of end-stage renal disease is higher among Aboriginals, but it is unknown whether this is due to an increased prevalence of chronic kidney disease or other unidentified factors. We studied 658,664 people of non-First Nations and 14,989 people of First Nations and found that the age- and sex-adjusted prevalence of chronic kidney disease was significantly higher among those of non-First Nations compared to those of First Nations (67.5 versus 59.5 per 1000 population; P < 0.0001). However, severe chronic kidney disease (estimated glomerular filtration rate <30 ml/min per 1.73 m2) was almost two-fold higher among people of First Nations (P < 0.0001). Cox proportional hazards models suggested that compared to people of non-First Nations, those of First Nations with chronic kidney disease had a 77% increased risk of death after adjusting for age, gender, diabetes and baseline eGFR. In conclusion, whether the higher incidence of end-stage renal disease among people of First Nations is due to suboptimal management of chronic kidney disease and its associated comorbidities, more rapid loss of kidney function, or other unidentified factors remains to be determined.

The association of poverty with the prevalence of albuminuria: data from the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND

Albuminuria is a major risk factor for the development and progression of chronic kidney disease (CKD) and cardiovascular disease. Socioeconomic factors also have been reported to modify CKD and cardiovascular risk factors and clinical outcomes. The extent to which poverty influences the prevalence of albuminuria, particularly among racial/ethnic minority populations, is not well established. The influence of poverty on the prevalence of albuminuria and the implication of this relationship for the racial and/or ethnic differences in the prevalence of albuminuria were examined.

METHODS

We examined data from 6,850 male and 7,634 female adults from a national probability survey conducted between 1988 and 1994.

RESULTS

In univariate analysis, poverty, defined as less than 200% federal poverty level (FPL), was associated with the presence of both microalbuminuria (odds ratio [OR], 1.35; 95% confidence interval, 1.22 to 1.49) and macroalbuminuria (OR, 1.78; 95% confidence interval, 1.40 to 2.26). The association of less than 200% FPL with microalbuminuria persisted in a multivariate model controlling for age, sex, race, education, obesity, hypertension, diabetes, reduced glomerular filtration rate, and medication use (OR, 1.18; 95% confidence interval, 1.05 to 1.33). FPL less than 200% was not associated with macroalbuminuria in the multivariate model. When multivariate analysis is stratified by FPL (<200% and > or =200%), differences in ORs for microalbuminuria and macroalbuminuria among racial/ethnic minority participants compared with whites were more apparent among the less affluent participants in the FPL-less-than-200% stratum.

CONCLUSION

FPL less than 200% is associated with microalbuminuria, and differences in FPL levels may account for some of the observed differences in prevalence of albuminuria between racial/ethnic minority participants and their white counterparts.

Quality of care among Aboriginal hemodialysis patients

Registry data report racial differences in hemodialysis (HD) care, with ethnic minorities at a disadvantage. However, little information is available regarding Aboriginal HD patients specifically. This study sought to compare the quality of HD care between Aboriginal and non-Aboriginal patients in Canada. All adults who were established on HD for > or = 6 mo in a single Canadian province were included. Clinical information was obtained by patient interview and chart review, with race determined by self-report. Quality of HD care was assessed by small solute clearance, BP control, mineral metabolism, and anemia management. Of the 835 patients, 95 (11.4%) were Aboriginal. Aboriginal patients were significantly younger, were more likely to have diabetes as the cause of ESRD, and had a higher degree of comorbidity than non-Aboriginal patients. There were no differences between Aboriginal and non-Aboriginal patients for small solute clearance, anemia management, or use of permanent vascular access. Aboriginal patients, however, were less likely to achieve a target predialysis systolic BP of < 140 mmHg (29.5 versus 44.9%; P = 0.004), a target phosphate level of < 1.8 mmol/L (40.0 versus 67.3%; P < 0.0001), and a calcium-phosphate product < 4.4 mmol2/L2 (52.6 versus 72.7%; P < 0.001). Quality of care was found to be similar for Aboriginal compared with non-Aboriginal HD patients except for differences in predialysis systolic BP and mineral metabolism, which may be influenced by individual and cultural factors. Explanations for these differences and their impact on morbidity and mortality warrant further investigation.

Disparity in outcomes for adult Native American hemodialysis patients? Findings from the ESRD Clinical Performance Measures Project, 1996 to 1999

BACKGROUND

There is a paucity of information regarding the quality of care for Native American hemodialysis patients. Outcomes, including 1-year hospitalization and mortality, for adult Native American in-center hemodialysis patients selected for the Centers for Medicare and Medicaid (CMS) end-stage renal disease (ESRD) Clinical Performance Measures (CPM) Project were compared to those for white and black patients to determine if disparity in care existed for this group.

METHODS

Clinical data were abstracted from medical records for the last quarters of 1995 to 1998 and linked to United States Renal Data System (USRDS) data files for data on comorbidities and 1-year hospitalization and mortality. Associations of race were tested by bivariate analyses and multivariate logistic regression and Cox proportional hazard modeling.

RESULTS

Two percent (467 of 27876) of patients were Native American, 37% black, and 51% white. Native American, compared to black and white patients, were more likely to have diabetes mellitus as the cause of ESRD (72%, 37%, and 38%, respectively, P < 0.01). In multivariate analyses, Native American patients were more likely to achieve a mean urea reduction ratio (URR) > or = 65% compared to whites (referent) [hazards ratio (HR) (95% CI) 1.7 (1.3, 2.2)] and be dialyzed with an arteriovenous fistula [HR (95% CI) 1.7 (1.2, 2.5)]. They were as likely as Whites to achieve a mean hematocrit > or =33% and a mean serum albumin > or =4.0/3.7 g/dL. In multivariate analyses, Native Americans were no more likely to be hospitalized or die during the follow-up period than whites.

CONCLUSION

These data suggest that adult Native American hemodialysis patients experience equivalent or better dialytic care and are no more likely to experience 1-year hospitalization or mortality compared to whites.

A population-based, cross-sectional survey of the Zuni Pueblo: a collaborative approach to an epidemic of kidney disease

Approximately 80% of the Zuni Indians live in Zuni Pueblo in rural New Mexico. The Zuni are relatively endogamous and differ culturally and ethnically from neighboring tribes. The Zuni Pueblo is experiencing an epidemic of renal disease. The prevalence of end-stage renal disease (ESRD) among the Zuni Indians, adjusted for age and gender, is 6-fold and 21-fold higher than the prevalence rates for Native Americans and European Americans. Almost all Zuni tribal members have a relative with ESRD. This has led to strong public support for renal research. In response, the Zuni community has partnered with the Indian Health Service (IHS), University of New Mexico Health Sciences Center (UNMHSC), Southwest Foundation for Biomedical Research (SFBR), Dialysis Clinic Inc (DCI), and the National Institutes of Health (NIH) to establish a research consortium, the Zuni Kidney Project (ZKP). The goal of the ZKP is to reduce the burden of renal disease in the Zuni community. The ZKP combines traditional, population-based, epidemiologic methods with modern techniques of population genetics. The foundation of the ZKP is a population-based, cross-sectional survey (PBCSS). The PBCSS has 3 specific aims: (1) estimate the prevalence of renal disease in Zuni; (2) assess risk factors for renal disease susceptibility; and (3) identify participants for planned case-control, longitudinal cohort, and family studies designed to identify environmental, familial, and genetic risk factors for the susceptibility and/or progression of renal disease. Preliminary results of the PBCSS confirm that the epidemic of renal disease in Zuni Indians is due to high rates of both diabetic and nondiabetic renal disease.

Microalbuminuria and pulse pressure in hypertensive and atherosclerotic men

To identify the biological covariates of microalbuminuria (albuminuria >/=15 microg/min) in nondiabetic subjects, brachial blood pressure, echocardiographic left ventricular mass, and other cardiovascular and metabolic parameters were evaluated in 211 untreated males (38 normal controls, 109 uncomplicated stage 1 to 3 essential hypertensives, and 64 patients with clinically stable atherosclerotic peripheral vascular disease either with [n=44] or without [n=20] essential hypertension) with normal cardiac and renal function. Compared with normoalbuminuric subjects, microalbuminuric subjects (n=67) were characterized by higher systolic blood pressure, comparable diastolic blood pressure, and, therefore, wider pulse pressure. Greater prevalence of hypertension, peripheral vascular disease, left ventricular hypertrophy, and reduced HDL cholesterol values further distinguished microalbuminuric from normoalbuminuric subjects in univariate comparisons. The risk of microalbuminuria increased by ascending pulse pressure quintiles in age-corrected logistic regression models, in which pulse pressure was more predictive than systolic pressure and was independent of mean pressure. When microalbuminuric status was regressed against a series of dichotomous (vascular and active smoker status) and continuous (age, pulse and mean pressure, left ventricular mass index, and HDL and LDL cholesterol) variables, only pulse pressure, left ventricular mass index, and smoking status were independent predictors. The association of increased albuminuria with wider pulse pressure, a correlate of the pulsatile hemodynamic load and conduit vessel stiffness as well as an important cardiovascular risk factor, may explain why microalbuminuria predicts cardiovascular events in nondiabetic subjects. The independence from concomitant vascular disease also suggests that wider pulse pressure, rather than representing a simple marker for atherosclerotic disease, influences albuminuria directly.