Albuminuria and racial disparities in the risk for ESRD

Incidence of hyperkalemia RAASi and SGLT-2i treatment in individuals with diabetic kidney disease: a systematic review and network meta-analysis

Background

This study aims to evaluate the incidence of hyperkalemia and serum potassium levels associated with the use of sodium-glucose cotransporter-2 inhibitors (SGLT-2i), renin-angiotensin-aldosterone system inhibitors (RAASi) and concurrent use of these medications in individuals with diabetic kidney disease (DKD).

Methods

A comprehensive systematic search was performed in EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, Scopus, and PubMed database, covering studies up to March 2024. Relevant randomized controlled trials (RCT) included adults with DKD who were treated with SGLT-2i and RAASi or their combination, with a minimum follow-up duration of 12 weeks. The primary outcomes assessed were the incidence of hyperkalemia and serum potassium levels were the primary outcomes assessed. The surface under the cumulative ranking curves (SUCRA) was utilized for ranking purposes.

Results

The study included 36 trials, encompassing 45,120 participants, comparing various interventions. SGLT-2i (SUCRA = 88.5%) was found to significantly reduce the risk of hyperkalemia. In contrast, the combination of ACEI/ARB + MRA (SUCRA = 5.7%) increased the risk of hyperkalemia. However, when SGLT-2i was added to the ACEI/ARB + MRA regimen, the incidence of hyperkalemia was found to decrease. Subgroup analyses on MRA showed that ACEI/ARB + spironolactone posed the highest risk of hyperkalemia. ACEI/ARB + SGLT-2i mitigated serum potassium level.

Conclusion

SGLT-2i was effective in reducing the incidence of hyperkalemia incidence, whereas a combination of ACEI/ARB and MRA might elevate the incidence of hyperkalemia in individuals with DKD.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/#recordDetails, identifier CRD42024552810.

Empagliflozin attenuating renal interstitial fibrosis in diabetic kidney disease by inhibiting lymphangiogenesis and lymphatic endothelial-to-mesenchymal transition via the VEGF-C/VEGFR3 pathway

Renal interstitial fibrosis (RIF) is a significant pathological change in diabetic kidney disease (DKD) that can be induced by endothelial-to-mesenchymal transition (EndMT). Lymphangiogenesis, mediated by the vascular endothelial growth factor-C (VEGF-C)/vascular endothelial growth factor receptor-3 (VEGFR-3) pathway, plays a crucial role in the development of RIF in DKD. Although numerous studies have demonstrated the efficacy of empagliflozin in treating renal injury, its effects on lymphangiogenesis in DKD-related RIF and the underlying mechanisms remain unclear. In the present study, significant lymphangiogenesis was assessed in the renal interstitium of patients with DKD. We subsequently explored the relationship between DKD-related RIF and lymphangiogenesis in mouse models, high-glucose (HG)-stimulated renal HK-2 cell lines, and human lymphatic endothelial cells (hLECs). Additionally, we evaluated the effects of empagliflozin on these processes. The results revealed that HG induces lymphangiogenesis, which exacerbates RIF by promoting inflammatory responses. Furthermore, hLECs directly contributed to the progression of DKD-related RIF through EndMT. Further analysis revealed that tubular epithelial cells (TECs) act as effector cells for VEGF-C, with the epithelial-to-mesenchymal transition (EMT) of TECs occurring concurrently with the EndMT of lymphatic vessels. Empagliflozin inhibited RIF in DKD by suppressing the VEGF-C/VEGFR3 pathway and reducing lymphangiogenesis. In conclusion, this study elucidates the interplay between lymphangiogenesis, EndMT, and RIF in DKD and provides new insights into the mechanism by which empagliflozin treats DKD.

Role of Age and Competing Risk of Death in the Racial Disparity of Kidney Failure Incidence after Onset of CKD

SIGNIFICANCE STATEMENT

Black adults in the United States have 2-4 times higher incidence of kidney failure than White adults. Yet, the reasons underlying this disparity remain poorly understood. Among 547,188 US veterans with new-onset CKD, according to a new race-free GFR equation, Black veterans had a 2.5-fold higher cumulative incidence of kidney failure, compared with White veterans, in any follow-up period from CKD onset. This disparity resulted from a combination of higher hazards of progression to kidney failure and lower hazards of competing-risk death in Black veterans. Both, in turn, were largely explained by the younger age at CKD onset in Black veterans, underscoring an urgent need to prevent early onset and slow progression of CKD in younger Black adults.

BACKGROUND

The Black adult population is well known to have higher incidence of kidney failure than their White counterpart in the United States, but the reasons underlying this disparity are unclear. We assessed the racial differences in kidney failure and death from onset of CKD on the basis of the race-free 2021 CKD Epidemiology Collaboration equation and examined the extent to which these differences could be explained by factors at the time of CKD onset.

METHODS

We analyzed a national cohort consisting of 547,188 US veterans (103,821 non-Hispanic Black and 443,367 non-Hispanic White), aged 18-85 years, with new-onset CKD between 2005 and 2016 who were followed through 10 years or May 2018 for incident kidney failure with replacement therapy (KFRT) and pre-KFRT death.

RESULTS

At CKD onset, Black veterans were, on average, 7.8 years younger than White veterans. In any time period from CKD onset, the cumulative incidence of KFRT was 2.5-fold higher for Black versus White veterans. Meanwhile, Black veterans had persistently >2-fold higher hazards of KFRT throughout follow-up (overall hazard ratio [95% confidence interval], 2.38 [2.31 to 2.45]) and conversely had 17%-48% decreased hazards of pre-KFRT death. These differences were reduced after accounting for the racial difference in age at CKD onset.

CONCLUSIONS

The 2.5-fold higher cumulative incidence of kidney failure in Black adults resulted from a combination of higher hazards of progression to kidney failure and lower hazards of the competing risk of death, both of which can be largely explained by the younger age at CKD onset in Black compared with White adults.

Genetic Inhibition of APOL1 Pore-Forming Function Prevents APOL1-Mediated Kidney Disease

SIGNIFICANCE STATEMENT

African Americans are at increased risk of CKD in part due to high-risk (HR) variants in the apolipoprotein L1 ( APOL1 ) gene, termed G1/G2. A different APOL1 variant, p.N264K , reduced the risk of CKD and ESKD among carriers of APOL1 HR variants to levels comparable with individuals with APOL1 low-risk variants in an analysis of 121,492 participants of African ancestry from the Million Veteran Program (MVP). Functional genetic studies in cell models showed that APOL1 p.N264K blocked APOL1 pore-forming function and ion channel conduction and reduced toxicity of APOL1 HR mutations. Pharmacologic inhibitors that mimic this mutation blocking APOL1 -mediated pore formation may be able to prevent and/or treat APOL1 -associated kidney disease.

BACKGROUND

African Americans are at increased risk for nondiabetic CKD in part due to HR variants in the APOL1 gene.

METHODS

We tested whether a different APOL1 variant, p.N264K , modified the association between APOL1 HR genotypes (two copies of G1/G2) and CKD in a cross-sectional analysis of 121,492 participants of African ancestry from the MVP. We replicated our findings in the Vanderbilt University Biobank ( n =14,386) and National Institutes of Health All of Us ( n =14,704). Primary outcome was CKD and secondary outcome was ESKD among nondiabetic patients. Primary analysis compared APOL1 HR genotypes with and without p.N264K . Secondary analyses included APOL1 low-risk genotypes and tested for interaction. In MVP, we performed sequential logistic regression models adjusting for demographics, comorbidities, medications, and ten principal components of ancestry. Functional genomic studies expressed APOL1 HR variants with and without APOL1 p.N264K in cell models.

RESULTS

In the MVP cohort, 15,604 (12.8%) had two APOL1 HR variants, of which 582 (0.5%) also had APOL1 p.N264K . In MVP, 18,831 (15%) had CKD, 4177 (3%) had ESKD, and 34% had diabetes. MVP APOL1 HR, without p.N264K , was associated with increased odds of CKD (odds ratio [OR], 1.72; 95% confidence interval [CI], 1.60 to 1.85) and ESKD (OR, 3.94; 95% CI, 3.52 to 4.41). In MVP, APOL1 p.N264K mitigated the renal risk of APOL1 HR, in CKD (OR, 0.43; 95% CI, 0.28 to 0.65) and ESKD (OR, 0.19; CI 0.07 to 0.51). In the replication cohorts meta-analysis, APOL1 p.N264K mitigated the renal risk of APOL1 HR in CKD (OR, 0.40; 95% CI, 0.18 to 0.92) and ESKD (OR, 0.19; 95% CI, 0.05 to 0.79). In the mechanistic studies, APOL1 p.N264K blocked APOL1 pore-forming function and ion channel conduction and reduced toxicity of APOL1 HR variants.

CONCLUSIONS

APOL1 p.N264K is associated with reduced risk of CKD and ESKD among carriers of APOL1 HR to levels comparable with individuals with APOL1 low-risk genotypes.

Interrelations between albuminuria, electrocardiographic left atrial abnormality, and incident atrial fibrillation in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort

BACKGROUND

The objective of the study was to examine the joint associations of albuminuria and electrocardiographic left atrial abnormality (ECG-LAA) with incident atrial fibrillation (AF) and whether this relationship varies by race.

METHODS

This analysis included 6670 participants free of clinical cardiovascular disease (CVD), including atrial fibrillation (AF), from the Multi-Ethnic Study of Atherosclerosis. ECG-LAA was defined as P-wave terminal force in V1 [PTFV1] >5000 μV × ms. Albuminuria was defined as urine albumin-creatinine ratio (UACR) ≥30 mg/g. Incident AF events through 2015 were ascertained from hospital discharge records and study-scheduled electrocardiograms. Cox proportional hazard models were used to examine the association of "no albuminuria + no ECG-LAA (reference)", "isolated albuminuria", "isolated ECG-LAA" and "albuminuria + ECG-LAA" with incident AF.

RESULTS

Over a median follow-up of 13.8 years, 979 incident cases of AF occurred. In adjusted models, the concomitant presence of ECG-LAA and albuminuria was associated with a higher risk of AF than either ECG-LAA or albuminuria in isolation (HR (95% CI): 2.43 (1.65-3.58), 1.33 (1.05-1.69), and 1.55 (1.27-1.88), respectively (interaction p-value = 0.50). Effect modification by race was observed with a 4-fold greater AF risk in Black participants with albuminuria + ECG-LAA (HR (95%CI): 4.37 (2.38-8.01) but no significant association in White participants (HR (95% CI) 0.60 (0.19-1.92) respectively; (interaction p-value for race x albuminuria-ECG-LAA combination = 0.05).

CONCLUSIONS

Concomitant presence of ECG-LAA and albuminuria confers a higher risk of AF compared to either one in isolation with a stronger association in Blacks than Whites.

Empagliflozin attenuates the renal tubular ferroptosis in diabetic kidney disease through AMPK/NRF2 pathway

Renal tubular damage plays a key role in the pathogenesis of diabetic kidney disease (DKD), and one of the main pathological process associated with DKD in diabetic mice is the ferroptosis, a novel form of cell death caused by iron-dependent lipid peroxidation. Several researches suggested that empagliflozin may treat renal injury, but its effects on diabetic-related ferroptosis and underlying mechanisms were not fully elucidated. In this study, the influence of empagliflozin on renal injury was evaluated in vivo and in vitro in a mouse model and in high-glucose (HG) or Erastin-stimulated renal HK-2 cell line, respectively. Ferroptosis-related markers were assessed, including GSH, labile iron levels, and ferroptosis regulators by Western blot, qRT-PCR, immunohistochemistry, and immunofluorescence. The level of malondialdehyde (MDA) and the fluorescence intensity of BODIPY probe indicated the level of lipid peroxidation. It was demonstrated that solute carrier family 7, member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) were less expressed in renal biopsy samples from patients affected by DKD than in those from non-diabetic renal disease patients (NDRD), proving the ferroptosis of tubular epithelial cells in case of DKD. Furthermore, empagliflozin markedly decreased the ferroptosis impairment in DKD mice, as well as in HG model of HK-2 cells. Our investigations showed the ability of empagliflozin to suppress ferroptosis was partially countered by AMP-activated protein kinase (AMPK) inhibitor, which led to a reduction of the nuclear translocation of the antioxidant transcription factor NFE2-related factor 2 (NRF2) and downregulation of target genes such as GPX4, ferritin heavy chain 1 (FTH1), and SLC7A11, while AMPK agonists were responsible for the enhancement of the protective effects of empagliflozin. Taken together, our findings showed that empagliflozin may prevent the development of ferroptosis by promoting the AMPK-mediated NRF2 activation pathway, providing important insights for possible novel treatment approaches for DKD.

Black and White Adults With CKD Hospitalized With Acute Kidney Injury: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

RATIONALE & OBJECTIVE

Few studies have investigated racial disparities in acute kidney injury (AKI), in contrast to the extensive literature on racial differences in the risk of kidney failure. We sought to study potential differences in risk in the setting of chronic kidney disease (CKD).

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

We studied 2,720 self-identified Black or White participants with CKD enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study from July 1, 2013, to December 31, 2017.

EXPOSURE

Self-reported race (Black vs White).

OUTCOME

Hospitalized AKI (≥50% increase from nadir to peak serum creatinine).

ANALYTICAL APPROACH

Cox regression models adjusting for demographics (age and sex), prehospitalization clinical risk factors (diabetes, blood pressure, cardiovascular disease, estimated glomerular filtration rate, proteinuria, receipt of angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers), and socioeconomic status (insurance status and education level). In a subset of participants with genotype data, we adjusted for apolipoprotein L1 gene (APOL1) high-risk status and sickle cell trait.

RESULTS

Black participants (n = 1,266) were younger but had a higher burden of prehospitalization clinical risk factors. The incidence rate of first AKI hospitalization among Black participants was 6.3 (95% CI, 5.5-7.2) per 100 person-years versus 5.3 (95% CI, 4.6-6.1) per 100 person-years among White participants. In an unadjusted Cox regression model, Black participants were at a modestly increased risk of incident AKI (HR, 1.22 [95% CI, 1.01-1.48]) compared with White participants. However, this risk was attenuated and no longer significant after adjusting for prehospitalization clinical risk factors (adjusted HR, 1.02 [95% CI, 0.83-1.25]). There were only 11 AKI hospitalizations among individuals with high-risk APOL1 risk status and 14 AKI hospitalizations among individuals with sickle cell trait.

LIMITATIONS

Participants were limited to research volunteers and potentially not fully representative of all CKD patients.

CONCLUSIONS

In this multicenter prospective cohort of CKD patients, racial disparities in AKI incidence were modest and were explained by differences in prehospitalization clinical risk factors.

A Step Toward Health Equity for Veterans: Evidence Supports Removing Race From Kidney Function Calculations

Background

The practice of race-based medicine fails to recognize that race cannot be used as a proxy for genetic ancestry and that racial and ethnic categories are complex sociopolitical constructs without biological basis. Clinical algorithms and equations that incorporate race modifiers and are currently considered standard for diagnosis and management of disease are appropriately being scrutinized for lack of biological plausibility and their role in exacerbating health inequities. In this paper, we review the history, evidence, and implications of using a Black race coefficient when calculating estimated glomerular filtration rate (eGFR) in the diagnosis and management of kidney disease.

Observations

Currently, the US Department of Veterans Affairs (VA) uses the Modification of Diet in Renal Disease (MDRD) equation for eGFR. This equation includes a Black race coefficient that results in an eGFR that is 21% higher for a Black patient when compared with a patient of any other race. The rationale for the inclusion of this coefficient is based on racist science that incorrectly assumes race as a proxy for genetic ancestry. Multiple studies across diverse Black populations demonstrate that the application of a race coefficient in kidney function estimation equations is inferior when compared with the race-neutral option. Furthermore, the most utilized eGFR equations are biased and imprecise. Because eGFR is the primary diagnostic method for detecting and managing kidney disease, preventing its progression, planning for dialysis, and evaluating for transplantation, it is vital that eGFR be as accurate, precise, and equitable as possible.

Conclusions

The incorporation of a race coefficient in kidney estimation equations lacks biological plausibility and its use exacerbates kidney health disparities. Until a better method to estimate kidney function becomes available, a race-neutral option for current estimation equations should be applied for all patients.

Characterization of ferroptosis in kidney tubular cell death under diabetic conditions

Kidney tubular cell death induced by transforming growth factor-β1 (TGF-β1) is known to contribute to diabetic nephropathy, a major complication of diabetes. Caspase-3-dependent apoptosis and caspase-1-dependent pyroptosis are also involved in tubular cell death under diabetic conditions. Recently, ferroptosis, an atypical form of iron-dependent cell death, was reported to cause kidney disease, including acute kidney injury. Ferroptosis is primed by lipid peroxide accumulation through the cystine/glutamate antiporter system Xc- (xCT) and glutathione peroxidase 4 (GPX4)-dependent mechanisms. The aim of this study was to evaluate the role of ferroptosis in diabetes-induced tubular injury. TGF-β1-stimulated proximal tubular epithelial cells and diabetic mice models were used for in vitro and in vivo experiments, respectively. xCT and GPX4 expression, cell viability, glutathione concentration, and lipid peroxidation were quantified to indicate ferroptosis. The effect of ferroptosis inhibition was also assessed. In kidney biopsy samples from diabetic patients, xCT and GPX4 mRNA expression was decreased compared to nondiabetic samples. In TGF-β1-stimulated tubular cells, intracellular glutathione concentration was reduced and lipid peroxidation was enhanced, both of which are related to ferroptosis-related cell death. Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, alleviated TGF-β1-induced ferroptosis. In diabetic mice, kidney mRNA and protein expressions of xCT and GPX4 were reduced compared to control. Kidney glutathione concentration was decreased, while lipid peroxidation was increased in these mice, and these changes were alleviated by Fer-1 treatment. Ferroptosis is involved in kidney tubular cell death under diabetic conditions. Ferroptosis inhibition could be a therapeutic option for diabetic nephropathy.

Toward Causally Interpretable Meta-analysis: Transporting Inferences from Multiple Randomized Trials to a New Target Population

We take steps toward causally interpretable meta-analysis by describing methods for transporting causal inferences from a collection of randomized trials to a new target population, one trial at a time and pooling all trials. We discuss identifiability conditions for average treatment effects in the target population and provide identification results. We show that the assumptions that allow inferences to be transported from all trials in the collection to the same target population have implications for the law underlying the observed data. We propose average treatment effect estimators that rely on different working models and provide code for their implementation in statistical software. We discuss how to use the data to examine whether transported inferences are homogeneous across the collection of trials, sketch approaches for sensitivity analysis to violations of the identifiability conditions, and describe extensions to address nonadherence in the trials. Last, we illustrate the proposed methods using data from the Hepatitis C Antiviral Long-Term Treatment Against Cirrhosis Trial.

Racial disparities in end-stage renal disease in a high-risk population: the Southern Community Cohort Study

INTRODUCTION

The Southern Community Cohort Study is a prospective study of low socioeconomic status (SES) blacks and whites from the southeastern US, where the burden of end-stage renal disease (ESRD) and its risk factors are high. We tested whether the 2.4-fold elevated risk of ESRD we previously observed in blacks compared to whites was explained by differences in baseline kidney function.

METHODS

We conducted a case-cohort study of incident ESRD cases (n = 737) with stored blood and a probability sampled subcohort (n = 4238) and calculated estimated glomerular filtration rate (eGFR) from serum creatinine. 86% of participants were enrolled from community health centers in medically underserved areas and 14% from the general population in 12 states in the southeastern United States. Incident ESRD after entry into the cohort was ascertained by linkage of the cohort with the US Renal Data System (USRDS).

RESULTS

Median (25th, 75th percentile) eGFR at baseline was 63.3 (36.0, 98.2) ml/min/1.73m2 for ESRD cases and 103.2 (86.0, 117.9) for subcohort. Black ESRD cases had higher median (25th, 75th) eGFR [63.3 (35.9, 95.9)] compared to whites [59.1 (39.4, 99.2)]. In multivariable Cox models accounting for sampling weights, baseline eGFR was a strong predictor of ESRD risk, and an interaction with race was detected (P = 0.029). The higher ESRD risk among blacks relative to whites persisted (hazard ratio: 2.58; 95% confidence interval: 1.65, 4.03) after adjustment for eGFR.

CONCLUSION

In this predominantly lower SES cohort, the racial disparity in ESRD risk is not explained by differences in baseline kidney function.

APOL1, Acid Load, and CKD Progression

INTRODUCTION

High dietary acid load and metabolic acidosis are associated with an accelerated decline in kidney function and may contribute to the observed heterogeneity in end-stage renal disease (ESRD) risk according to APOL1 genotype. Our objective was to examine the associations of metabolic acidosis and dietary acid load with kidney disease progression, according to APOL1 genotype, among individuals with chronic kidney disease (CKD).

METHODS

We studied 1048 African American participants in the Chronic Renal Insufficiency Cohort. Metabolic acidosis was defined as blood levels of serum bicarbonate less than 22 mEq/L, and dietary acid load was quantified by potential renal acid load (PRAL) using data from the Diet Health Questionnaire. APOL1 status was defined as having 2 risk variants, consisting of either possible combination of the G1 and G2 risk alleles. We tested associations of APOL1 and dietary and metabolic acidosis with CKD progression, defined as time to ESRD or 50% decline in eGFR.

RESULTS

During a median follow-up period of 7 years, 379 participants had an incident CKD progression event (6.4 events per 100 person-years). After full adjustment, among participants with 2 APOL1 variants, the analysis failed to detect an association between metabolic acidosis or dietary acid load and CKD progression (hazard ratio [HR], 1.03; 95% confidence interval [CI], 0.96-1.11 per 1 mEq/L higher serum bicarbonate and an HR, 1.03; 95% CI, 0.92-1.15 per 10 mEq/L higher PRAL). Similar associations were noted among participants without the APOL1 high-risk genotype.

CONCLUSION

In a population at high risk of developing ESRD, metabolic acidosis and dietary acid load were not associated with CKD progression.

Socioeconomic disadvantage and the risk of advanced chronic kidney disease: results from a cohort study with 1.4 million participants

Background

Several studies have investigated the effect of socioeconomic deprivation on cardiovascular disease (CVD) and diabetes; less is known about its effect on chronic kidney disease (CKD). We aimed to measure the association between deprivation, CKD Stages 4–5 and end-stage renal disease (ESRD) in a general population sample.

Methods

This observational study examined 1 405 016 participants from the English Clinical Practice Research Datalink (2000–14), linked to hospital discharge data and death certification. Deprivation was assessed according to the participant’s postcode. Cox models were used to estimate hazard ratios (HRs) for CKD Stages 4–5 and ESRD, adjusting for age and sex, and additionally for smoking status, body mass index, diabetes, systolic blood pressure, prior CVD and estimated glomerular filtration rate (eGFR) at baseline.

Results

During 7.5 years of median follow-up, 11 490 individuals developed CKD Stages 4–5 and 1068 initiated ESRD. After adjustment for age and sex, the HRs and confidence interval (CI) comparing those in the 20% most deprived of the population to the 20% least deprived were 1.76 (95% CI 1.68–1.84) and 1.82 (95% CI 1.56–2.12) for CKD Stages 4–5 and ESRD, respectively. Further adjustment for known risk factors and eGFR substantially attenuated these HRs. Adding our results to all known cohort studies produced a pooled relative risk of 1.61 (95% CI 1.42–1.83) for ESRD, for comparisons between highest to lowest categories of deprivation.

Conclusion

Socioeconomic deprivation is independently associated with an increased hazard of CKD Stages 4–5 and ESRD, but in large part may be mediated by known risk factors.

Generalizability of SPRINT-CKD cohort to CKD patients referred to renal clinics

BACKGROUND

The Systolic Blood Pressure Intervention Trial-CKD substudy (SPRINT-CKD) has suggested a lower blood pressure (BP) target in CKD patients. However, it is questionable whether the SPRINT-CKD results may be generalized to CKD patients under nephrology care.

METHODS

To compare SPRINT-CKD cohort versus referred CKD patients in terms of patients' risk profile and outcomes, we pooled four prospective cohorts of consecutive CKD patients referred to 40 Italian renal clinics. We implemented the same inclusion/exclusion criteria adopted in SPRINT and same endpoints: (1) a composite of fatal and non-fatal cardiovascular (CV) events (2) all-cause mortality and (3) ESRD (composite of chronic dialysis, transplantation or 50% eGFR decline). Findings were compared with those attained in the control arm of SPRINT-CKD trial that mirrored standard BP management in clinical practice.

RESULTS

Out of 2847 patients referred to renal clinics, only 20.1% (n = 571) were identified as eligible for SPRINT-CKD. Age (72 ± 9 years), gender (42.2% female) and systolic BP (142 ± 10 mmHg) did not differ from the SPRINT-CKD while referred patients had a worse risk profile at baseline: larger prevalence of prior CV disease (25.7% versus 19.5%), higher Framingham risk score (31.9 ± 14.6% versus 27.2 ± 24.7%) and lower GFR (38 ± 11 versus 48 ± 10 mL/min/1.73 m²). During 4.0 years of follow-up, 86 CV events (50 fatal), 78 all-cause death and 59 ESRD occurred with annual incidence rates higher than those observed in the SPRINT-CKD control group (CV events 4.18 vs 3.19; all-cause death 3.64 vs 2.21; ESRD 2.80 vs 0.41%/year).

CONCLUSIONS

The SPRINT-CKD cohort is poorly representative of the CKD population under nephrology care, thus suggesting that conclusions may not apply to patients referred to nephrologist.

Ten-year risk prediction models of complications and mortality of Chinese patients with diabetes mellitus in primary care in Hong Kong: a study protocol

INTRODUCTION

Diabetes mellitus (DM) is a major disease burden worldwide because it is associated with disabling and lethal complications. DM complication risk assessment and stratification is key to cost-effective management and tertiary prevention for patients with diabetes in primary care. Existing risk prediction functions were found to be inaccurate in Chinese patients with diabetes in primary care. This study aims to develop 10-year risk prediction models for total cardiovascular diseases (CVD) and all-cause mortality among Chinese patients with DM in primary care.

METHODS AND ANALYSIS

A 10-year cohort study on a population-based primary care cohort of Chinese patients with diabetes, who were receiving care in the Hospital Authority General Outpatient Clinic on or before 1 January 2008, were identified from the clinical management system database of the Hospital Authority. All patients with complete baseline risk factors will be included and followed from 1 January 2008 to 31 December 2017 for the development and validation of prediction models. The analyses will be carried out separately for men and women. Two-thirds of subjects will be randomly selected as the training sample for model development. Cox regressions will be used to develop 10-year risk prediction models of total CVD and all-cause mortality. The validity of models will be tested on the remaining one-third of subjects by Harrell's C-statistics and calibration plot. Risk prediction models for diabetic complications specific to Chinese patients in primary care will enable accurate risk stratification, prioritisation of resources and more cost-effective interventions for patients with DM in primary care.

ETHICS AND DISSEMINATION

The study was approved by the Institutional Review Board of the University of Hong Kong-the Hospital Authority Hong Kong West Cluster (reference number: UW 15-258).

TRIAL REGISTRATION NUMBER

NCT03299010; Pre-results.

ESRD and ESRD-DM associated with lignite-containing aquifers in the U.S. Gulf Coast region of Arkansas, Louisiana, and Texas

Balkan endemic nephropathy (BEN) is an irreversible, lethal kidney disease that occurs in regions of the Balkans where residents drink untreated well water. A key factor contributing to the development of BEN may be consumption of dissolved organic matter leached from low-rank coal called lignite. This hypothesis-known as lignite-water hypothesis-was first posed for areas of the Balkans. It is possible that a BEN-like condition exists in the United States (US) Gulf Coast region in parts of the Mississippi Embayment and the Texas Coastal Uplands aquifers -Arkansas, Louisiana, and Texas, for instance-that rely heavily on groundwater from aquifers that contain lignite. This study utilizes a geographic information system (GIS) to map the distributions of end-stage renal disease (ESRD) in relation to water from lignite-containing aquifers in the tri-state region. Regional patterns emerged from geospatial analysis, suggesting that counties that relied on lignite-containing aquifers for their main water source had higher rates of ESRD in comparison to other populations in the region that rely on other water sources, including surface water and groundwater from aquifers not associated with lignite seams. Statewide rates of ESRD and diabetes associated ESRD (ESRD-DM) showed strong correlations to the percent of families at or below poverty level and the percentage of African Americans. These confounding factors somewhat mitigate the association seen between ESRD and lignite-containing regions at the state level. However, at the larger tri-state view, there is a significant (p = 0.002) increase in incidence rates where groundwater is connected to lignite-containing aquifers when considering both race and poverty. Additionally, no relationship was observed between the rate of public water supply withdrawal from lignite-bearing aquifers and rates of ESRD or ESRD-DM at the state or tri-state regions, supporting the observation that the risk associated with water from lignite-containing aquifers is limited to water from untreated domestic supply.

Race/Ethnicity, Dietary Acid Load, and Risk of End-Stage Renal Disease among US Adults with Chronic Kidney Disease

BACKGROUND

Dietary acid load (DAL) contributes to the risk of CKD and CKD progression. We sought to determine the relation of DAL to racial/ethnic differences in the risk of end-stage renal disease (ESRD) among persons with CKD.

METHODS

Among 1,123 non-Hispanic black (NHB) and non-Hispanic white (NHW) National Health and Nutrition Examination Survey III participants with estimated glomerular filtration rate 15-59 mL/min/1.73 m2, DAL was estimated using the Remer and Manz net acid excretion (NAEes) formula and 24-h dietary recall. ESRD events were ascertained via linkage with Medicare. A competing risk model (accounting for death) was used to estimate the hazard ratio (HR) for treated ESRD, comparing NHBs with NHWs, adjusting for demographic, clinical and nutritional factors (body surface area, total caloric intake, serum bicarbonate, protein intake), and NAEes. Additionally, whether the relation of NAEes with ESRD risk varied by race/ethnicity was tested.

RESULTS

At baseline, NHBs had greater NAEes (50.9 vs. 44.2 mEq/day) than NHWs. It was found that 22% developed ESRD over a median of 7.5 years. The unadjusted HR comparing NHBs to NHWs was 3.35 (95% CI 2.51-4.48) and adjusted HR (for factors above) was 1.68 (95% CI 1.18-2.38). A stronger association of NAE with risk of ESRD was observed among NHBs (adjusted HR per mEq/day increase in NAE 1.21, 95% CI 1.12-1.31) than that among NHWs (HR 1.08, 95% CI 0.96-1.20), p interaction for race/ethnicity × NAEes = 0.004.

CONCLUSIONS

Among US adults with CKD, the association of DAL with progression to ESRD is stronger among NHBs than NHWs. DAL is worthy of further investigation for its contribution to kidney outcomes across race/ethnic groups.

Chronic kidney disease and incident apparent treatment-resistant hypertension among blacks: Data from the Jackson Heart Study

It is unclear whether black patients with chronic kidney disease (CKD) vs those without CKD who take antihypertensive medication have an increased risk for apparent treatment-resistant hypertension (aTRH). The authors analyzed 1741 Jackson Heart Study participants without aTRH taking antihypertensive medication at baseline. aTRH was defined as uncontrolled blood pressure while taking three antihypertensive medication classes or taking four or more antihypertensive medication classes, regardless of blood pressure level. CKD was defined as an albumin to creatinine ratio ≥30 mg/g or estimated glomerular filtration rate <60 mL/min/1.73 m² . Over 8 years, 20.1% of participants without CKD and 30.5% with CKD developed aTRH. The multivariable-adjusted hazard ratio for aTRH comparing participants with CKD vs those without CKD was 1.45 (95% CI, 1.12-1.86). Participants with an albumin to creatinine ratio ≥30 vs <30 mg/g (hazard ratio, 1.44; 95% CI, 1.04-2.00) and estimated glomerular filtration rate of 45 to 59 mL/min/1.73 m² and <45 vs ≥60mL/min/1.73 m² (hazard ratio, 1.60 [95% CI, 1.16-2.20] and 2.05 [95% CI, 1.28-3.26], respectively) were more likely to develop aTRH.

Prediction of new onset of end stage renal disease in Chinese patients with type 2 diabetes mellitus - a population-based retrospective cohort study

BACKGROUND

Since diabetes mellitus (DM) is the leading cause of end stage renal disease (ESRD), this study aimed to develop a 5-year ESRD risk prediction model among Chinese patients with Type 2 DM (T2DM) in primary care.

METHODS

A retrospective cohort study was conducted on 149,333 Chinese adult T2DM primary care patients without ESRD in 2010. Using the derivation cohort over a median of 5 years follow-up, the gender-specific models including the interaction effect between predictors and age were derived using Cox regression with a forward stepwise approach. Harrell's C-statistic and calibration plot were applied to the validation cohort to assess discrimination and calibration of the models.

RESULTS

Prediction models showed better discrimination with Harrell's C-statistics of 0.866 (males) and 0.862 (females) and calibration power from the plots than other established models. The predictors included age, usages of anti-hypertensive drugs, anti-glucose drugs, and Hemogloblin A1c, blood pressure, urine albumin/creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR). Specific predictors for male were smoking and presence of sight threatening diabetic retinopathy while additional predictors for female included longer duration of diabetes and quadratic effect of body mass index. Interaction factors with age showed a greater weighting of insulin and urine ACR in younger males, and eGFR in younger females.

CONCLUSIONS

Our newly developed gender-specific models provide a more accurate 5-year ESRD risk predictions for Chinese diabetic primary care patients than other existing models. The models included several modifiable risk factors that clinicians can use to counsel patients, and to target at in the delivery of care to patients.

Chronic Kidney Disease and Risk for Gastrointestinal Bleeding in the Community: The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND OBJECTIVES

Patients on dialysis are known to have higher risk for gastrointestinal (GI) bleeding. However, data on mild to moderate CKD, particularly elevated albuminuria, are limited.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 11,088 participants in the Atherosclerosis Risk in Communities (ARIC) Study, we investigated the association of eGFR and urinary albumin-to-creatinine ratio (ACR) with risk for hospitalization with GI bleeding. Kidney measures were assessed at visit four (1996-1998), and follow-up was continued through 2011.

RESULTS

During a median follow-up of 13.9 years, 686 first incident hospitalizations with GI bleeding were observed (incidence rate, 4.9 per 1000 person-years [95% confidence interval (95% CI), 4.5 to 5.3]). Multivariable Cox proportional hazards models revealed that both lower eGFR and higher ACR were associated with higher risk for GI bleeding. With eGFR≥90 ml/min per 1.73 m2 as a reference, risk for GI bleeding was significant in moderately decreased eGFR of 30-59 ml/min per 1.73 m2 (hazard ratio [HR], 1.51; 95% CI, 1.13 to 2.02), and was highest in severely decreased eGFR<30 ml/min per 1.73 m2 (HR, 7.06; 95% CI, 3.91 to 12.76). Compared with ACR<10 mg/g, risk for GI bleeding became significantly higher in mild albuminuria with ACR 10-29 mg/g (HR, 1.36; 95% CI, 1.08 to 1.69), and was nearly double in moderate and severe albuminuria (HR, 2.13; 95% CI, 1.66 to 2.71 for ACR 30-299 mg/g, and HR, 2.07; 95% CI, 1.33 to 3.22 for ACR≥300 mg/g). These results were largely consistent in demographic and clinical subgroups and independent of incident cardiovascular events or dialysis during follow-up.

CONCLUSIONS

Individuals with even mild to moderate CKD warrant clinical attention regarding the risk of hospitalization with GI bleeding.

Risk of ESRD in the United States

BACKGROUND

Although incidence rates of end-stage renal disease (ESRD) in the United States are reported routinely by the US Renal Data System (USRDS), risks (probabilities) are not reported. Short- and long-term risk estimates need to be updated and expanded to minority populations, including Native Americans, Asian/Pacific Islanders, and Hispanics.

STUDY DESIGN

Risk estimation from surveillance data in large populations using life-table methods. A competing-risks framework was applied by constructing a hypothetical cohort followed from birth to death.

SETTING & PARTICIPANTS

Total US population. Incidence and mortality rates of ESRD were obtained from the USRDS; all-cause mortality rates were obtained from CDC WONDER.

PREDICTORS

Age, sex, race/ethnicity, and year.

OUTCOMES

10-year to lifetime risks (cumulative incidence) of ESRD.

RESULTS

Among males, lifetime risks of ESRD from birth using 2013 data were 3.1% (95% CI, 3.0%-3.1%) for non-Hispanic whites, 8.0% (95% CI, 7.9%-8.2%) for non-Hispanic blacks, 3.8% (95% CI, 3.4%-4.9%) for non-Hispanic Native Americans, 5.1% (95% CI, 4.8%-5.4%) for non-Hispanic Asians/Pacific Islanders, and 6.2% (95% CI, 6.1%-6.4%) for Hispanics. Among females, lifetime risks were 2.0% (95% CI, 2.0%-2.1%) for non-Hispanic whites, 6.8% (95% CI, 6.7%-6.9%) for non-Hispanic blacks, 3.6% (95% CI, 3.3%-4.2%) for non-Hispanic Native Americans, 3.8% (95% CI, 3.6%-4.0%) for non-Hispanic Asian/Pacific Islanders, and 4.3% (95% CI, 4.2%-4.5%) for Hispanics. Lifetime risk of ESRD from birth increased from 3.5% in 2000 to 4.0% in 2013 in males and decreased from 3.0% to 2.8% in females.

LIMITATIONS

Standard life-time assumption of fixed age-specific rates over time and possible ESRD misclassification. To be useful in clinical practice, this application will require additional predictors (eg, comorbid conditions and chronic kidney disease stage).

CONCLUSIONS

ESRD risk in the United States varies more than 2-fold among racial/ethnic groups for both sexes.

Effects of Race and Sex on Measured GFR: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Kidney failure disproportionately affects older blacks versus whites. The reasons are unknown and may be related to lower measured glomerular filtration rate (GFR) and higher levels of albuminuria in community-based population samples.

STUDY DESIGN

Cross-sectional analysis of a substudy of a prospective cohort.

SETTING & PARTICIPANTS

Ancillary study following Multi-Ethnic Study of Atherosclerosis (MESA) visit 5.

PREDICTOR

Age, sex, and race.

OUTCOMES & MEASUREMENTS

Measured GFR using plasma clearance of iohexol and urine albumin-creatinine ratio (ACR).

RESULTS

GFR was measured in 294 participants. Mean age was 71±9 (SD) years, 47% were black, 48% were women, mean GFR was 73±19mL/min/1.73m², and median ACR was 10.0 (IQR, 5.8-20.9) mg/g. Measured GFR was on average 1.02 (95% CI, 0.79-1.24) mL/min/1.73m² lower per year older. Mean GFR indexed for body surface area was not different between blacks versus whites (mean difference, 2.94 [95% CI, -1.37 to 7.26] mL/min/1.73m²), but was lower in women than men (mean difference, -9.34 [95% CI, -13.53 to -5.15] mL/min/1.73m²); this difference persisted and remained significant after adjustment for demographics, clinical characteristics, and measures of body size. The difference between men and women, but not between blacks and whites, was substantially greater when GFR was not indexed for body surface area. ACR was higher in older versus younger participants (mean difference, 3.2% [95% CI, 1.5%-4.8%] per year), but geometric mean ratio of ACR did not differ between blacks versus whites (mean difference, 19.7%; 95% CI, -39.1% to 6.1%) or between men versus women (mean difference, -4.4%; 95% CI, -27.7% to 26.3%).

LIMITATIONS

This is a study of survivors. People who agreed to participate were younger than those who refused.

CONCLUSIONS

In this first community-based study that included blacks and whites, no differences in measured GFR between races were found, suggesting that other factors must account for the disproportionately higher burden of kidney failure in older blacks versus whites.

Association between insurance status and mortality in individuals with albuminuria: an observational cohort study

BACKGROUND

In the general population, the association between uninsurance and mortality is well established. We sought to evaluate the association of health insurance status with mortality among working-age participants with albuminuria in the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES III).

METHODS

We used data from non-elderly adult participants (18-64) of NHANES III (1988-1994), a nationally representative study of the US civilian, noninstitutionalized population, who provided information on insurance and who had albuminuria, defined as a urine albumin-to-creatinine ratio [UACR] ≥ 30 mg/g and their subsequent mortality to December 31, 2006. Cox proportional hazards models were used to determine associations between insurance status and all-cause mortality and cardiovascular mortality in patients with CKD while adjusting in a stepwise fashion for sociodemographic factors, co-morbidities, and co-morbidity severity/control covariates.

RESULTS

In our sample of individuals with albuminuria (n = 903), mean estimated glomerular filtration rate (eGFR) was 101.6 ml/min/1.73 m(2) with 4.7 % with an eGFR <60. Approximately 15 % of the sample was uninsured, 18 % had public insurance and 67 % had private insurance. Compared to individuals with private insurance, those with public insurance or no insurance were significantly more likely to be a racial or ethnic minority, to have income <200 % below the federal poverty level, to have less than high school education; and they were less likely to be married and to report good or excellent health, all p < 0.05. Being uninsured or having public insurance was associated with increased all-cause mortality in the fully adjusted model (HR 2.97 and 3.65, respectively, p < 0.05). There was no significant relationship between insurance status and cardiovascular mortality.

CONCLUSIONS

In a nationally representative sample of individuals with albuminuria, uninsurance and public insurance were associated with increased mortality compared to the private insurance even after controlling for sociodemographic, health status, and health care variables. Improving access to care and the quality of care received may potentially reduce mortality in individuals with evidence of early CKD.

Association of sleep duration with kidney function and albuminuria: NHANES 2009-2012

OBJECTIVE

The purpose of this study was to examine the association between self-reported sleep duration and markers of kidney function.

DESIGN

A cross-sectional survey from the 2009-2012 National Health and Nutrition Examination Survey.

SETTING AND PARTICIPANTS

The participants were 8690 adults (e20years) without a previous sleep disorder diagnosis, end-stage kidney failure, or other kidney or liver problems. Subsamples with pre-diabetes and pre-hypertension were examined.

MEASUREMENTS

Participants reported habitual sleep duration, coded as d5, 6, 7, 8, and e9hours per night. Biomarkers of kidney function were determined, including glomerular filtration rate (eGFR) estimated from the Chronic Kidney Disease Epidemiology Collaboration equation, urine albumin-to-creatinine ratio (ACR), microalbuminuria status, and glomerular hyperfiltration status. Weighted and adjusted general linear models assessed associations between sleep duration with eGFR and ACR. Logistic regression analyses evaluated the associations of microalbuminuria and glomerular hyperfiltration status with sleep duration.

RESULTS

Greater eGFR was related to short sleep duration in the total sample and among participants with pre-diabetes. Greater ACR was associated with short and long sleep duration. Short sleep duration (d5hours) was associated with an increased odds for glomerular hyperfiltration (OR, 1.41; 95% CI, 0.97-2.06) and microalbuminuria (OR, 1.31; 95% CI, 0.96-1.79).

CONCLUSIONS

In a US representative sample of adults, self-reported short and long sleep duration were related to higher ACR. Short sleep duration was associated with higher eGFR and microalbuminuria. Research is needed to understand whether these associations indicate increased risk for kidney damage and cardiovascular risk.

Food Access, Chronic Kidney Disease, and Hypertension in the U.S

INTRODUCTION

Greater distance to full-service supermarkets and low income may impair access to healthy diets and contribute to chronic kidney disease (CKD) and hypertension. The study aim was to determine relationships among residence in a "food desert," low income, CKD, and blood pressure.

METHODS

Adults in the 2003-2010 National Health and Nutrition Examination Survey (N=22,173) were linked to food desert data (www.ers.usda.gov) by Census Tracts. Food deserts have low median income and are further from a supermarket or large grocery store (>1 mile in urban areas, >10 miles in rural areas). Weighted regression was used to determine the association of residence in a food desert and family income with dietary intake; systolic blood pressure (SBP); and odds of CKD. Data analysis was performed in 2014-2015.

RESULTS

Compared with those not in food deserts, participants residing in food deserts had lower levels of serum carotenoids (p<0.01), a biomarker of fruit and vegetable intake, and higher SBP (1.53 mmHg higher, 95% CI=0.41, 2.66) after adjustment for demographics and income. Residence in a food desert was not associated with odds of CKD (OR=1.20, 95% CI=0.96, 1.49). Lower, versus higher, income was associated with lower serum carotenoids (p<0.01) and higher SBP (2.00 mmHg higher for income-poverty ratio ≤1 vs >3, 95% CI=1.12, 2.89), but also greater odds of CKD (OR=1.76 for income-poverty ratio ≤1 vs >3, 95% CI=1.48, 2.10).

CONCLUSIONS

Limited access to healthy food due to geographic or financial barriers could be targeted for prevention of CKD and hypertension.

Disparities in Electronic Health Record Patient Portal Use in Nephrology Clinics

BACKGROUND AND OBJECTIVES

Electronic health record (EHR) patient portals allow individuals to access their medical information with the intent of patient empowerment. However, little is known about portal use in nephrology patients. We addressed this gap by characterizing adoption of an EHR portal, assessing secular trends, and examining the association of portal adoption and BP control (<140/90 mmHg).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients seen between January 1, 2010, and December 31, 2012, at any of four university-affiliated nephrology offices who had at least one additional nephrology follow-up visit before June 30, 2013, were included. Sociodemographic characteristics, comorbidities, clinical measurements, and office visits were abstracted from the EHR. Neighborhood median household income was obtained from the American Community Survey 2012.

RESULTS

Of 2803 patients, 1098 (39%) accessed the portal. Over 87% of users reviewed laboratory results, 85% reviewed their medical information (e.g., medical history), 85% reviewed or altered appointments, 77% reviewed medications, 65% requested medication refills, and 31% requested medical advice from their renal provider. In adjusted models, older age, African-American race (odds ratio [OR], 0.50; 95% confidence interval [95% CI], 0.39 to 0.64), Medicaid status (OR, 0.53; 95% CI, 0.36 to 0.77), and lower neighborhood median household income were associated with not accessing the portal. Portal adoption increased over time (2011 versus 2010: OR, 1.38 [95% CI, 1.09 to 1.75]; 2012 versus 2010: OR, 1.95 [95% CI, 1.44 to 2.64]). Portal adoption was correlated with BP control in patients with a diagnosis of hypertension; however, in the fully adjusted model this was somewhat attenuated and no longer statistically significant (OR, 1.11; 95% CI, 0.99 to 1.24).

CONCLUSION

While portal adoption appears to be increasing, greater attention is needed to understand why vulnerable populations do not access it. Future research should examine barriers to the use of e-health technologies in underserved patients with CKD, interventions to address them, and their potential to improve outcomes.

Race and ethnicity influences on cardiovascular and renal events in patients with diabetes mellitus

BACKGROUND

The incidence of end-stage renal disease (ESRD) has been consistently shown to be higher among blacks and Hispanics compared to whites with unmeasured risk factors and access to care as suggested explanations. In a high-risk cohort with frequent protocol-directed follow-up, we evaluated the influence of race on cardiovascular (CV) outcomes and incidence of ESRD.

METHODS

TREAT was a randomized, double-blind, placebo-controlled study. This secondary analysis focused on role of race on outcomes. TREAT enrolled 4,038 patients with type 2 diabetes, chronic kidney disease (estimated glomerular filtration rate 20-60 mL/min per 1.73 m(2)), and anemia (hemoglobin level ≤11 g/dL) treated with either darbepoetin alfa or placebo. We compared self-described black and Hispanic patients to white patients with regard to baseline characteristics and outcomes, including mortality, CV outcomes (myocardial infarction, stroke, heart failure, resuscitated sudden death, and coronary revascularization), and incident ESRD. Multivariate adjusted Cox models were developed for these outcomes.

RESULTS

Black and Hispanic patients were younger, more likely women, had less prior CV disease, and higher blood pressure. During a mean follow-up of 2.4 years with comparable access to care, blacks and Hispanics had a greater risk of ESRD but a significant lower risk of myocardial infarction and coronary revascularization than whites. After adjusting for confounders, blacks remained at significantly greater risk of ESRD than whites (hazard ratio 1.53, 95% CI 1.26-1.85, P < .001), whereas this ESRD risk did not persist among Hispanics.

CONCLUSION

Despite similar access to care and lower CV event rates, the risk of ESRD was higher among blacks and Hispanics than whites. For blacks, but not Hispanics, this increase was independent of known attributable risk factors.

Renal cell cancer histological subtype distribution differs by race and sex

OBJECTIVES

To examine racial differences in the distribution of histological subtypes of renal cell carcinoma (RCC) and associations with established RCC risk factors by subtype.

MATERIALS AND METHODS

Tumours from 1532 consecutive patients with RCC who underwent nephrectomy at Vanderbilt University Medical Center (1998-2012) were classified as clear-cell, papillary, chromophobe and other subtypes. In pairwise comparisons, we used multivariate logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between race, sex, age, end-stage renal disease (ESRD) and body mass index at diagnosis according to histological subtype.

RESULTS

The RCC subtype distribution was significantly different in black people from that in white people (P < 0.001), with a substantially higher proportion of patients with papillary RCC among black people than white people (35.7 vs 13.8%). In multivariate analyses, compared with clear-cell RCC, people with papillary RCC were significantly more likely to be black (OR 4.15; 95% CI 2.64-6.52) and less likely to be female (OR 0.60; 95% CI 0.43-0.83). People with chromophobe RCC were significantly more likely to be female (OR 2.32; 95% CI 1.44-3.74). Both people with papillary RCC (OR 6.26; 95% CI 2.75-14.24) and those with chromophobe RCC (OR 7.07; 95% CI 2.13-23.46) were strongly and significantly more likely to have ESRD, compared with those with clear-cell RCC.

CONCLUSION

We observed marked racial differences in the proportional subtype distribution of RCCs diagnosed at a large tertiary care academic centre. To our knowledge, no previous study has examined racial differences in the distribution of RCC histologies while adjusting for ESRD, which was the factor most strongly associated with papillary and chromophobe RCC compared with clear-cell RCC.

Racial differences in circulating natriuretic peptide levels: the atherosclerosis risk in communities study

Background

Natriuretic peptides promote natriuresis, diuresis, and vasodilation. Experimental deficiency of natriuretic peptides leads to hypertension (HTN) and cardiac hypertrophy, conditions more common among African Americans. Hospital-based studies suggest that African Americans may have reduced circulating natriuretic peptides, as compared to Caucasians, but definitive data from community-based cohorts are lacking.

Methods and Results

We examined plasma N-terminal pro B-type natriuretic peptide (NTproBNP) levels according to race in 9137 Atherosclerosis Risk in Communities (ARIC) Study participants (22% African American) without prevalent cardiovascular disease at visit 4 (1996–1998). Multivariable linear and logistic regression analyses were performed adjusting for clinical covariates. Among African Americans, percent European ancestry was determined from genetic ancestry informative markers and then examined in relation to NTproBNP levels in multivariable linear regression analysis. NTproBNP levels were significantly lower in African Americans (median, 43 pg/mL; interquartile range [IQR], 18, 88) than Caucasians (median, 68 pg/mL; IQR, 36, 124; P<0.0001). In multivariable models, adjusted log NTproBNP levels were 40% lower (95% confidence interval [CI], −43, −36) in African Americans, compared to Caucasians, which was consistent across subgroups of age, gender, HTN, diabetes, insulin resistance, and obesity. African-American race was also significantly associated with having nondetectable NTproBNP (adjusted OR, 5.74; 95% CI, 4.22, 7.80). In multivariable analyses in African Americans, a 10% increase in genetic European ancestry was associated with a 7% (95% CI, 1, 13) increase in adjusted log NTproBNP.

Conclusions

African Americans have lower levels of plasma NTproBNP than Caucasians, which may be partially owing to genetic variation. Low natriuretic peptide levels in African Americans may contribute to the greater risk for HTN and its sequalae in this population.

Gender differences in preclinical markers of kidney injury in a rural north Carolina african-american cohort

Introduction: The incidence rate of end-stage renal disease (ESRD) is highest among African-American (AA) males. The reason for this disparity in ESRD for AA males remains unclear, but it is well established that diabetes is the leading risk factor. Prediabetes may also be a risk for kidney disease since prediabetics have increased risk for cardiovascular disease and often do not receive drug interventions unless their hemoglobin A1c (A1c) level is above 6%. Perhaps, AA males are at greater risk because they often are untreated prediabetics and this predisposes them to renal injury. Therefore, we hypothesize that prediabetic AA males have higher albumin:creatinine ratio (ACr), a biomarker of renal injury, than their female counterparts.

Methods: Male and female AAs were recruited (53 females and 47 males; 45 ± 2 years old) from a rural northeastern region of NC. Blood and urine samples were collected for A1c and albumin measurements, respectively. Participants were stratified based on their A1c levels: non-diabetic: <5.7%, prediabetic: ≥5.7% but <6.5%, and diabetic: ≥6.5%.

Results: The proportion of males that are normal, prediabetic, and diabetic differed from that of females (p = 0.002). Interestingly, prediabetic men tended to be younger (41 ± 4 vs. 51 ± 3, respectively; p = 0.027) than prediabetic females (p = 0.027). A1c and ACr were not associated with blood pressure in males or females. AA males had a relative risk of 0.9, 2.5, and 1.4 for microalbuminuria for non-diabetic, prediabetic, and diabetic, respectively, compared to AA females.

Conclusion: These results support our hypothesis that AA males may be predisposed to prediabetes kidney injury compared to their female counterpart. Thus, young AA males should be screened for biomarkers of kidney injury even if they have normal glucose and blood pressure levels.

The association between race and income on risk of mortality in patients with moderate chronic kidney disease

Background

Socioeconomic status (SES) is independently associated with chronic kidney disease (CKD) progression; however, its association with other CKD outcomes is unclear. In particular, the potential differential effect of SES on mortality among blacks and whites is understudied in CKD. We aimed to examine survival among individuals with prevalent CKD by income and race in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study.

Methods

We examined 2,761 participants with prevalent CKD stage 3 or 4 between 2003 and 2007 in the REGARDS cohort. Participants were followed through March 2013. Mortality from any cause was assessed by income and race (black or white). Low income was defined as an annual household income < $20,000, and was compared to higher incomes (≥$20,000). Cox proportional hazards models adjusted for age, gender, education, insurance, CKD stage, comorbidity and county-level poverty were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

Results

A total of 750 deaths (27.5%) occurred during the follow-up period. Average follow-up time was 6.6 years among those alive and 3.7 years among those who died. Low income participants had an elevated adjusted hazard of mortality (HR = 1.58, 95% CI 1.24-2.00) compared to higher income participants. Low income was associated with all-cause mortality regardless of race (HR 1.53; 95% CI 1.18-1.99 among blacks and HR 1.38; 95% CI 1.10-1.74 among whites), with no significant statistical interaction between household income and race (p-value = 0.634). However, black participants had a higher adjusted hazard of mortality (HR = 1.30, 95% CI 1.02-1.65) compared to whites, which was independent of income.

Conclusion

Income was associated with increased mortality for both blacks and whites with CKD. Blacks with CKD had higher mortality than whites even after adjusting for important socio-demographic and clinical factors.

Explaining the racial difference in AKI incidence

African Americans face higher risk of AKI than Caucasians. The extent to which this increased risk is because of differences in clinical, socioeconomic, or genetic risk factors is unknown. We evaluated 10,588 African-American and Caucasian participants in the Atherosclerosis Risk in Communities study, a community-based prospective cohort of middle-aged individuals. Participants were followed from baseline study visit (1996-1999) to first hospitalization for AKI (defined by billing code), ESRD, death, or December 31, 2010. African-American participants were slightly younger (61.7 versus 63.1 years, P<0.001), were more often women (64.5% versus 53.2%, P<0.001), and had higher baseline eGFR compared with Caucasians. Annual family income, education level, and prevalence of health insurance were lower among African Americans than Caucasians. The unadjusted incidence of hospitalized AKI was 7.4 cases per 1000 person-years among African Americans and 5.8 cases per 1000 person-years among Caucasians (P=0.002). The elevated risk of AKI among African Americans persisted after adjustment for demographics, cardiovascular risk factors, kidney markers, and time-varying number of hospitalizations (adjusted hazard ratio, 1.20; 95% confidence interval [95% CI], 1.01 to 1.43; P=0.04); however, accounting for differences in income and/or insurance by race attenuated the association (P>0.05). High-risk APOL1 variants did not associate with AKI among African Americans (demographic-adjusted hazard ratio, 1.07; 95% CI, 0.69 to 1.65; P=0.77). In summary, the higher risk of AKI among African Americans may be related to disparities in socioeconomic status.

25-Hydroxyvitamin D testing and supplementation in CKD: an NKF-KDOQI controversies report

The benefits of and thresholds for 25-hydroxyvitamin D administration in individuals with chronic kidney disease (CKD) remain uncertain. In this report, NKF-KDOQI (National Kidney Foundation-Kidney Disease Outcomes Quality Initiative) endeavors to provide health care providers with the latest information on a controversial area in the management of CKD, the role for nutritional vitamin D. Although knowledge of the biological mechanisms of vitamin D for bone maintenance in individuals with all stages of CKD has expanded, no consensus currently exists within the medical community regarding methods for 25-hydroxyvitamin D supplementation or optimal 25-hydroxyvitamin D levels in individuals with CKD. Within this report, existing CKD guidelines are summarized and scrutinized and ongoing clinical trials are cited as sources for future guidance on the optimal management of vitamin D in CKD.

Race and the insulin resistance syndrome

Type 2 diabetes remains an important cause of morbidity and mortality. The metabolic syndrome affects 25% of the adult US population based on the Third Report of the Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults from the National Cholesterol Education Program. Knowledge on the impact of obesity on metabolic health parameters has increased greatly over the past decade. This review discusses the limitations of the National Cholesterol Education Program metabolic syndrome definition and the racial disparities in the clinical presentation of the insulin resistance syndrome. We also examine the current literature with particular emphasis on albuminuria, nonalcoholic fatty liver disease, and intramyocellular lipid content. This review explores potential environmental and genetic reasons for differences in the manifestation of insulin resistance across racial/ethnic groups and highlights several promising areas for further study.

Socioeconomic factors and racial disparities in kidney disease outcomes

African Americans suffer disproportionately from advanced and progressive chronic kidney disease (CKD). Socioeconomic factors are believed to play an important role in this disparity, and likely influence African Americans' increased risk of CKD through multiple pathways. Low socioeconomic status (SES) may contribute to racial disparities in CKD because of the greater prevalence of poverty, for example, among African Americans as compared with whites. However, low SES has a stronger relation with CKD among African Americans than among whites, underscoring that the context and magnitude of socioeconomic influences on CKD outcomes varies between these populations. These socioeconomic influences may produce new or potentiate existing racial differences in biology. This review discusses what is known about the role of SES in explaining racial disparities in CKD, highlights several knowledge gaps in this area, and suggests future directions toward the elimination of disparities in CKD.

Association of increased travel distance to dialysis units with the risk of anemia in rural chronic hemodialysis elderly

Geographic remoteness has been found to influence health-related outcomes negatively. As reported in the literature, rural dialysis patients have a higher risk of mortality with increasing travel distance to dialysis units. However, few studies have focused on the impact of travel distances on the development of dialysis complications. We utilized a prospectively collected chronic hemodialysis patient cohort from a rural regional hospital for analysis. Data on demographics, comorbidities, and serum laboratory results were obtained. Correlation analyses between travel distance to dialysis units and dialysis complications were conducted, and significantly correlated parameters were entered into multivariate logistic regression models to determine their exact associations. A total of 46 rural chronic hemodialysis patients were enrolled, with an average age higher than others in the literature. Significant correlation was found between travel distance and serum hemoglobin levels (R(2) = -0.34, P value = 0.029). Multivariate logistic regression found that every 1 km increase in travel distance was associated with an increased risk of anemia (hemoglobin <9 g/dL) (odds ratio 1.46; P value = 0.01). Sensitivity analyses further showed that the associated risk was partially attenuated by serum albumin (odds ratio 1.83; P value = 0.07) and ferritin (odds ratio 1.39; P value = 0.08) levels. This is the first study to demonstrate the association between increased travel distance to dialysis units and the risk of anemia in chronic dialysis patients, especially elderly. Malnutrition, inflammation, and atherosclerosis syndrome could be partially responsible for the observed association. Further research is required to confirm our findings.

Cystatin C, a novel indicator of renal function, reflects severity of cerebral microbleeds

BACKGROUND

Chronic renal insufficiency, diagnosed using creatinine based estimated glomerular filtration rate (GFR) or microalbumiuria, has been associated with the presence of cerebral microbleeds (CMBs). Cystatin C has been shown to be a more sensitive renal indicator than conventional renal markers. Under the assumption that similar pathologic mechanisms of the small vessel exist in the brain and kidney, we hypothesized that the levels of cystatin C may delineate the relationship between CMBs and renal insufficiency by detecting subclinical kidney dysfunction, which may be underestimated by other indicators, and thus reflect the severity of CMBs more accurately.

METHODS

Data was prospectively collected for 683 patients with ischemic stroke. The severity of CMBs was categorized by the number of lesions. Patients were divided into quartiles of cystatin C, estimated GFR and microalbumin/creatinine ratios. Ordinal logistic regression analysis was used to examine the association of each renal indicator with CMBs.

RESULTS

In models including both quartiles of cystatin C and estimated GFR, only cystatin C quartiles were significant (the highest vs. the lowest, adjusted OR, 1.88; 95% CI 1.05-3.38; p = 0.03) in contrast to estimated GFR (the highest vs. the lowest, adjusted OR, 1.28; 95% CI 0.38-4.36; p = 0.70). A model including both quartiles of cystatin C and microalbumin/creatinine ratio also showed that only cystatin C quartiles was associated with CMBs (the highest vs. the lowest, adjusted OR, 2.06; 95% CI 1.07-3.94; p = 0.03). These associations were also observed in the logistic models using log transformed-cystatin C, albumin/creatinine ratio and estimated GFR as continuous variables. Cystatin C was a significant indicator of deep or infratenorial CMBs, but not strictly lobar CMBs. In addition, cystatin C showed the greatest significance in c-statistics for the presence of CMBs (AUC = 0.73 ± 0.03; 95% CI 0.66-0.76; p = 0.02).

CONCLUSION

Cystatin C may be the most sensitive indicator of CMB severity among the renal disease markers.

Association of proteinuria threshold in pre-eclampsia with maternal and perinatal outcomes: a nested case control cohort of high risk women

OBJECTIVES

To evaluate occurrence of adverse maternal and perinatal outcomes with different thresholds of proteinuria (300-499 mg and ≥500 mg/24 hours) in pre-eclamptic women, comparing outcomes against women with chronic and gestational hypertension.

DESIGN

Secondary analysis of the Vitamins in Pre-Eclampsia Trial.

SETTING

25 UK hospitals in ten geographical areas.

POPULATION

946 women with pre-existing risk factors for pre-eclampsia.

METHODS

Women with pre-eclampsia and proteinuria 300-499 mg/24 h (PE300, referent group, n=60) or proteinuria ≥500 mg/24 h (PE500, n=161) were compared with two groups of non-proteinuric women with chronic hypertension (CHT, n=615) or gestational hypertension (GH, n=110).

MAIN OUTCOME MEASURES

MATERNAL: progression to severe hypertension. Perinatal: small for gestational age (SGA) <5(th) centile, gestation at delivery.

RESULTS

Severe hypertension occurred more frequently in PE500 (35%) and PE300 (27%) than CHT (5.9%; P≤0.01) and GH (10%; p≤0.001). Gestation at delivery was earlier in PE500 (33.2 w) than PE300 (37.3 w; P≤0.001), and later in CHT (38.3 w; P≤0.05) and GH (39.1 w; P≤0.001). SGA infants were more frequent in PE300 (32%) than in CHT (13.3%; P≤0.001) and GH (16.5%; P≤0.05). Women in PE500 were more likely to have a caesarean section than PE300 (78% vs. 48%; P≤0.001), and to receive magnesium sulphate (17% vs. 1.7%, P≤0.05).

CONCLUSION

Women with PE300 have complication rates above those of women managed as out-patients (GH and CHT), meriting closer surveillance and confirming 300 mg/d as an appropriate threshold for determining in-patient management. Adverse perinatal outcomes are higher still in women with PE500.

Derivation and validation of a renal risk score for people with type 2 diabetes

OBJECTIVE

Diabetes has become the leading cause of end-stage renal disease (ESRD). Renal risk stratification could assist in earlier identification and targeted prevention. This study aimed to derive risk models to predict ESRD events in type 2 diabetes in primary care.

RESEARCH DESIGN AND METHODS

The nationwide derivation cohort included adults with type 2 diabetes from the New Zealand Diabetes Cohort Study initially assessed during 2000-2006 and followed until December 2010, excluding those with pre-existing ESRD. The outcome was fatal or nonfatal ESRD event (peritoneal dialysis or hemodialysis for ESRD, renal transplantation, or death from ESRD). Risk models were developed using Cox proportional hazards models, and their performance was assessed in a separate validation cohort.

RESULTS

The derivation cohort included 25,736 individuals followed for up to 11 years (180,497 person-years; 86% followed for ≥5 years). At baseline, mean age was 62 years, median diabetes duration 5 years, and median HbA1c 7.2% (55 mmol/mol); 37% had albuminuria; and median estimated glomerular filtration rate (eGFR) was 77 mL/min/1.73 m2. There were 637 ESRD events (2.5%) during follow-up. Models that included sex, ethnicity, age, diabetes duration, albuminuria, serum creatinine, systolic blood pressure, HbA1c, smoking status, and previous cardiovascular disease status performed well with good discrimination and calibration in the derivation cohort and the validation cohort (n=5,877) (C-statistics 0.89-0.92), improving predictive performance compared with previous models.

CONCLUSIONS

These 5-year renal risk models performed very well in two large primary care populations with type 2 diabetes. More accurate risk stratification could facilitate earlier intervention than using eGFR and/or albuminuria alone.

Association between urinary albumin excretion and coronary heart disease in black vs white adults

IMPORTANCE

Excess urinary albumin excretion is more common in black than white individuals and is more strongly associated with incident stroke risk in black vs white individuals. Whether similar associations extend to coronary heart disease (CHD) is unclear.

OBJECTIVE

To determine whether the association of urinary albumin excretion with CHD events differs by race.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study of black and white US adults aged 45 years and older who were enrolled within the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study between 2003 and 2007 with follow-up through December 31, 2009. We examined race-stratified associations of urinary albumin-to-creatinine ratio (ACR) in 2 groups: (1) incident CHD among 23,273 participants free of CHD at baseline; and (2) first recurrent CHD event among 4934 participants with CHD at baseline.

MAIN OUTCOMES AND MEASURES

Expert-adjudicated incident and recurrent myocardial infarction and acute CHD death.

RESULTS

A total of 616 incident CHD events (421 nonfatal MIs and 195 CHD deaths) and 468 recurrent CHD events (279 nonfatal MIs and 189 CHD deaths) were observed over a mean time of 4.4 years of follow-up. Among those free of CHD at baseline, age- and sex-adjusted incidence rates of CHD per 1000 person-years of follow-up increased with increasing categories of ACR in black and white participants, with rates being nearly 1.5-fold greater in the highest category of ACR (>300 mg/g) in black participants (20.59; 95% CI, 14.36-29.51) vs white participants (13.60; 95% CI, 7.60-24.25). In proportional hazards models adjusted for traditional cardiovascular risk factors and medications, higher baseline urinary ACR was associated with greater risk of incident CHD among black participants (hazard ratio [HR] comparing ACR >300 vs <10 mg/g, 3.21 [95% CI, 2.02-5.09]) but not white participants (HR comparing ACR >300 vs <10 mg/g, 1.49 [95% CI, 0.80-2.76]) (P value for interaction = .03). Among those with CHD at baseline, fully adjusted associations of baseline urinary ACR with first recurrent CHD event were similar between black participants (HR comparing ACR >300 vs <10 mg/g, 2.21 [95% CI, 1.22-4.00]) vs white participants (HR comparing ACR >300 vs <10 mg/g, 2.48 [95% CI, 1.61-3.78]) (P value for interaction = .53).

CONCLUSIONS AND RELEVANCE

Higher urinary ACR was associated with greater risk of incident but not recurrent CHD in black individuals when compared with white individuals. These data confirm that black individuals appear more susceptible to vascular injury.

Lifetime incidence of CKD stages 3-5 in the United States

BACKGROUND

Lifetime risk estimates of chronic kidney disease (CKD) can motivate preventative behaviors at the individual level and forecast disease burden and health care use at the population level.

STUDY DESIGN

Markov Monte Carlo model simulation study.

SETTING & POPULATION

Current US black and white population.

MODEL, PERSPECTIVE, & TIMEFRAME

Markov models simulating kidney disease development, using an individual perspective and lifetime horizon.

OUTCOMES

Age-, sex-, and race-specific residual lifetime risks of CKD stages 3a+ (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m²), 3b+ (eGFR <45 mL/min/1.73 m²), 4+ (eGFR <30 mL/min/1.73 m²), and end-stage renal disease (ESRD).

MEASUREMENTS

State transition probabilities of developing CKD and of dying prior to its development were modeled using: (1) mortality rates from the National Vital Statistics Report, (2) mortality risk estimates from a 2-million person meta-analysis, and (3) CKD prevalence from National Health and Nutrition Examination Surveys. Incidence, prevalence, and mortality related to ESRD were supplied by the US Renal Data System.

RESULTS

At birth, the overall lifetime risks of CKD stages 3a+, 3b+, 4+, and ESRD were 59.1%, 33.6%, 11.5%, and 3.6%, respectively. Women experienced greater CKD risk yet lower ESRD risk than men; blacks of both sexes had markedly higher CKD stage 4+ and ESRD risks (lifetime risks for white men, white women, black men, and black women, respectively: CKD stage 3a+, 53.6%, 64.9%, 51.8%, and 63.6%; CKD stage 3b+, 29.0%, 36.7%, 33.7%, and 40.2%; CKD stage 4+, 9.3%, 11.4%, 15.8%, and 18.5%; and ESRD, 3.3%, 2.2%, 8.5%, and 7.8%). Risk of CKD increased with age, with approximately one-half the CKD stage 3a+ cases developing after 70 years of age.

LIMITATIONS

CKD incidence was modeled from prevalence estimates in the US population.

CONCLUSIONS

In the United States, the lifetime risk of developing CKD stage 3a+ is high, emphasizing the importance of primary prevention and effective therapy to reduce CKD-related morbidity and mortality.

Host APOL1 genotype is independently associated with proteinuria in HIV infection

Proteinuria is associated with adverse clinical outcomes in HIV infection. Here we evaluated whether APOL1 risk alleles, previously associated with advanced kidney disease, are independently associated with proteinuria in HIV infection in a cross-sectional study of HIV-infected women in the Women's Interagency HIV Study. We estimated the percent difference in urine protein excretion and odds of proteinuria (≥200 mg/g) associated with two versus one or no APOL1 risk allele using linear and logistic regression, respectively. Of 1285 women successfully genotyped, 379 carried one and 80 carried two risk alleles. Proteinuria was present in 124 women, 78 of whom had proteinuria confirmed on a second sample. In women without prior AIDS, two risk alleles were independently associated with a 69% higher urine protein excretion (95% confidence interval (CI): 36, 108) and five-fold higher odds of proteinuria (95% CI: 2.45, 10.37) as compared with one or no risk allele. No association was found in women with prior AIDS. Analyses in which women with impaired kidney function were excluded and proteinuria was confirmed by a second urine sample yielded similar estimates. Thus, APOL1 risk alleles are associated with significant proteinuria in HIV-infected persons without prior clinical AIDS, independent of clinical factors traditionally associated with proteinuria. Trials are needed to determine whether APOL1 genotyping identifies individuals who could benefit from earlier intervention to prevent overt renal disease.

Lifestyle-related factors, obesity, and incident microalbuminuria: the CARDIA (Coronary Artery Risk Development in Young Adults) study

BACKGROUND

Modifiable lifestyle-related factors are associated with risk of coronary heart disease and may also influence kidney disease risk.

STUDY DESIGN

Community-based prospective cohort study.

SETTING & PARTICIPANTS

2,354 African American and white participants aged 28-40 years without baseline microalbuminuria or estimated glomerular filtration rate <60 mL/min/1.73 m² recruited from 4 US centers: Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA.

FACTORS

Current smoking, physical activity, fast food habits, obesity, and diet quality, which was based on 8 fundamental components of the Dietary Approaches to Stop Hypertension (DASH) diet, including increased intake of fruits, vegetables, low-fat dairy products, whole grains, and nuts and legumes and reduced intake of sodium, sugar-sweetened beverages, and red and processed meats.

OUTCOMES & MEASUREMENTS

Spot urine albumin-creatinine ratios were obtained at baseline (1995-1996) and three 5-year follow-up examinations (5, 10, and 15 years' follow-up). Incident microalbuminuria was defined as the presence of age- and sex-adjusted albumin-creatinine ratio ≥25 mg/g at 2 or more of the successive follow-up examinations.

RESULTS

During the 15-year follow-up, 77 (3.3%) individuals developed incident microalbuminuria. After multivariable adjustment, poor diet quality (OR, 2.0; 95% CI, 1.1-3.4) and obesity (OR, 1.9; 95% CI, 1.1-3.3) were associated significantly with microalbuminuria; current smoking (OR, 1.6; 95% CI, 0.9-2.8) was associated with microalbuminuria, although the CI crossed 1.0. Neither low physical activity (OR, 1.0; 95% CI, 0.5-1.8) nor fast food consumption (OR, 1.2; 95% CI, 0.7-2.3) was associated with microalbuminuria. Compared with individuals with no unhealthy lifestyle-related factors (poor diet quality, current smoking, and obesity), adjusted odds of incident microalbuminuria were 131%, 273%, and 634% higher for the presence of 1 (OR, 2.3; 95% CI, 1.3-4.3), 2 (OR, 3.7; 95% CI, 1.8-7.7), and 3 (OR, 7.3; 95% CI, 2.1-26.1) unhealthy lifestyle-related factors.

LIMITATIONS

Self-reported dietary history and physical activity, low number of outcomes.

CONCLUSIONS

Consuming an unhealthy diet and obesity are associated with incident microalbuminuria.

Urine arsenic and prevalent albuminuria: evidence from a population-based study

BACKGROUND

Long-term arsenic exposure is a major global health problem. However, few epidemiologic studies have evaluated the association of arsenic with kidney measures. Our objective was to evaluate the cross-sectional association between inorganic arsenic exposure and albuminuria in American Indian adults from rural areas of Arizona, Oklahoma, and North and South Dakota.

STUDY DESIGN

Cross-sectional. SETTING & PARTIPANTS: Strong Heart Study locations in Arizona, Oklahoma, and North and South Dakota. 3,821 American Indian men and women aged 45-74 years with urine arsenic and albumin measurements.

PREDICTOR

Urine arsenic.

OUTCOMES

Urine albumin-creatinine ratio and albuminuria status.

MEASUREMENTS

Arsenic exposure was estimated by measuring total urine arsenic and urine arsenic species using inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography-ICPMS, respectively. Urine albumin was measured by automated nephelometric immunochemistry.

RESULTS

The prevalence of albuminuria (albumin-creatinine ratio ≥30 mg/g) was 30%. Median value for the sum of inorganic and methylated arsenic species was 9.7 (IQR, 5.8-15.6) μg per gram of creatinine. Multivariable-adjusted prevalence ratios of albuminuria (albumin-creatinine ratio ≥30 mg/g) comparing the 3 highest to lowest quartiles of the sum of inorganic and methylated arsenic species were 1.16 (95% CI, 1.00-1.34), 1.24 (95% CI, 1.07-1.43), and 1.55 (95% CI, 1.35-1.78), respectively (P for trend <0.001). The association between urine arsenic and albuminuria was observed across all participant subgroups evaluated and was evident for both micro- and macroalbuminuria.

LIMITATIONS

The cross-sectional design cannot rule out reverse causation.

CONCLUSIONS

Increasing urine arsenic concentrations were cross-sectionally associated with increased albuminuria in a rural US population with a high burden of diabetes and obesity. Prospective epidemiologic and mechanistic evidence is needed to understand the role of arsenic as a kidney disease risk factor.