Estimated GFR and incident cardiovascular disease events in American Indians: the Strong Heart Study

Global disease burden attributable to kidney dysfunction, 1990-2019: A health inequality and trend analysis based on the global burden of disease study

OBJECTIVE

This study aimed to evaluate the burden of kidney dysfunction (KD), assess socioeconomic inequalities, and project trends in the future.

METHODS

Data on deaths, disability-adjusted life years (DALYs), years lived with disability (YLDs), and years of life lost (YLLs) were from Global Burden of Disease Study 2019. The Joinpoint regression model was utilized to analyze the temporal trend by the annual percentage change (APC). The slope index and concentration index were employed to evaluate cross-country disparities. The future trend was predicted using an age-period-cohort analysis.

RESULTS

In the past three decades, the death numbers of KD increased from 1,571,720 to 3,161,552, DALYs from 42,090,331 to 76,486,945, YLDs from 5,003,267 to 11,282,484, and YLLs from 37,087,065 to 65,204,461, respectively. The age-standardized rate (ASR) of deaths, DALYs, and YLLs exhibited a declining trend. The ASR of YLDs increased until 2017, then decreased. The slope index and concentration index for DALYs increased from 248.1 to 351.9 and from 40.70 to 57.8. In the future, the ASR of deaths, DALYs, YLDs, and YLLs will remain stable, while their numbers will continue to rise, except for YLLs.

CONCLUSIONS

The disease burden of KD remained serious. Tailored interventions should be developed based on national contexts.

Donor Evaluation of Living Kidney Transplantation in the Aging Society

BACKGROUND

Because of the lack of organ donation, living kidney transplantation (LKT) is increasing worldwide. Recently, the number of elderly donors has been increasing, and the patients with end-stage kidney diseases are older than those in the previous decades. Due to the advanced ages, their glomerular filtration rates (GFR) decrease, and the comorbidities such as hypertension, diabetic condition, and obesity are common. The clinicians now have to give their unwilling consent to the LKT from the donors with expanded criteria.

SUMMARY

For the secure selection of donors, proper GFR measuring is essential. Although directly measured GFR (mGFR) was recommended in the guidelines, estimated GFR (eGFR) is used at the initial evaluation of donor renal function clinically. Many equations calculating eGFR have been published so far. In the selection of eGFR equations, the smaller difference between mGFR and eGFR and the closer relationship to the prevalence rates of comorbidities are requisite points. Therefore, we compared the specificity of the various eGFR equations. The eGFR calculated from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation showed approximate reliability with minimal difference between mGFR and eGFR and the closer relationships to the prevalence rates of comorbidities.

KEY MESSAGE

The CKD-EPI-eGFR presented optimal performance in the donor renal function evaluation. Therefore, eGFR from the CKD-EPI equation is highly recommended in evaluating renal function in LKT donors.

Racial and Ethnic Differences in Chronic Kidney Disease and Its Risk Factors among Asian-Americans and Pacific Islanders in Hawaii

BACKGROUND

Several studies suggest that Asian-American and Native Hawaiian and Other Pacific Islander (NHOPI) racial/ethnic groups have a heightened risk of chronic kidney disease (CKD), but provide limited inference due to the aggregation of these groups into a single racial/ethnic category. We thus examined the association of granularly defined racial/ethnic groups with specific CKD indicators among a diverse group of participants from the National Kidney Foundation of Hawaii's Kidney Early Detection Screening (KEDS) Program.

METHODS

Among 1,243 participants enrolled in 19 KEDS screening events over 2006-2009, we examined the association between Asian-American and NHOPI groups and specific CKD indicators, defined as self-reported CKD, microalbuminuria, and macroalbuminuria, using multivariable logistic regression. We then examined associations of race/ethnicity with various CKD risk factors.

RESULTS

The most predominant racial/ethnic groups were White (22.0%), Multiracial (18.9%), Japanese (19.2%), Filipino (13.4%), NHOPI (8.4%), and Chinese (4.5%) participants. NHOPI and Chinese participants had a higher risk of microalbuminuria (adjusted ORs [aORs] [95% CIs] 2.48 [1.25-4.91] and 2.37 [1.07-5.27], respectively), while point estimates for all other minority groups suggested higher risk (reference: Whites). NHOPI participants also had a higher risk of macroalbuminuria and self-reported CKD. While most minorities had a higher risk of diabetes and hypertension, NHOPI and Multiracial participants had a higher risk of obesity, whereas the East Asian groups had a lower risk.

CONCLUSIONS

In this community-based cohort, compared with Whites, Asian-Americans had a higher risk of early CKD indicators, whereas NHOPIs had a higher risk of more severe CKD indicators. Further studies are needed to elucidate the distinct pathways leading to CKD across diverse racial/ethnic groups in Hawaii.

Multi-system trajectories and the incidence of heart failure in the Framingham Offspring Study

BACKGROUND

Heart failure is a multi-system disease, with non-cardiac systems playing a key role in disease pathogenesis.

OBJECTIVE

Investigate whether longitudinal multi-system trajectories incrementally predict heart failure risk compared to single-occasion traits.

METHODS

We evaluated 3,412 participants from the Framingham Heart Study Offspring cohort, free of heart failure, who attended examination cycle 5 and at least one examination between 1995-2008 (mean age 67 years, 54% women). We related trajectories for the following organ systems and metabolic functions to heart failure risk using Cox regression: kidney (estimated glomerular filtration rate), lung (forced vital capacity and the ratio of forced expiratory volume in one second/forced vital capacity), neuromotor (gait time), muscular (grip strength), cardiac (left ventricular mass index and heart rate), vascular function (pulse pressure), cholesterol (ratio of total/high-density lipoprotein), adiposity (body mass index), inflammation (C-reactive protein) and glucose homeostasis (hemoglobin A1c). Using traits selected via forward selection, we derived a trajectory risk score and related it to heart failure risk.

RESULTS

We observed 276 heart failure events during a median follow up of 10 years. Participants with the 'worst' multi-system trajectory profile had the highest heart failure risk. A one-unit increase in the trajectory risk score was associated with a 2.72-fold increase in heart failure risk (95% CI 2.21-3.34; p<0.001). The mean c-statistics for models including the trajectory risk score and single-occasion traits were 0.87 (95% CI 0.83-0.91) and 0.83 (95% CI 0.80-0.86), respectively.

CONCLUSION

Incorporating multi-system trajectories reflective of the aging process may add incremental information to heart failure risk assessment when compared to using single-occasion traits.

The Modified Chronic Kidney Disease Epidemiology Collaboration Equation for the Estimated Glomerular Filtration Rate Is Better Associated with Comorbidities than Other Equations in Living Kidney Donors in Japan

Objective We studied three types of estimated glomerular filtration rate (eGFR) equations and evaluated which type was strongly associated with comorbidities in living kidney transplantation (LKT) donors. Methods We compared the Japanese modified eGFR, Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration equations (Jm-eGFR, Jm-MDRD, and Jm-CKD-EPI, respectively) for Japanese LKT donors with respect to their relationships with obesity, hypertension, diabetes, cardiovascular disease, and stroke. Results Of the 8,176 enrolled Japanese LKT donors, the eGFR calculated using Jm-CKD-EPI (eGFR/Jm-CKD-EPI) detected significant differences in 4 of 5 comorbidities between the comorbidity-positive and comorbidity-negative groups, whereas the eGFR calculated using Jm-MDRD (eGFR/Jm-MDRD) and Jm-eGFR (eGFR/Jm-eGFR) detected only 3 and 1 comorbidities, respectively. The area under the receiver operating characteristic curve of Jm-CKD-EPI was larger than those of Jm-eGFR and Jm-MDRD for all five comorbidities. Conclusion We found that the eGFR/Jm-CKD-EPI correlated better with comorbidities than the eGFR/Jm-eGFR and eGFR/Jm-MDRD in Japanese LKT donors. We recommend using the eGFR/Jm-CKD-EPI for the initial assessment of the renal function in LKT donor candidates when evaluating the presence of associated comorbidities.

Glomerular filtration function decline, mortality, and cardiovascular events: data from the Strong Heart Study

BACKGROUND

Rapid kidney decline is associated with mortality and cardiovascular disease, even in the absence of chronic kidney disease. American Indians (AI) have particularly high burden of kidney disease, cardiovascular disease, and stroke. This study aims to examine extreme loss in glomerular function in this population in association with clinical outcomes.

METHODS

The Strong Heart Study, a large longitudinal cohort of adult AI participants, collected plasma creatinine at 3 examination visits between 1989-1999. Intraindividual regressions of estimated glomerular filtration rate (eGFR) provided linear estimates of change in kidney function over this time period. Surveillance with physician adjudication identified mortality and cardiovascular events between visit 3 through 2017.

RESULTS

Mean change in eGFR was loss 6.8 mL/min over the ten year baseline (range: -66.0 to +28.9 mL/min). The top 1 percentile lost approximately 5.7 mL/min/year. Participants with extreme eGFR loss were more likely to have diabetes (95% vs 71%), hypertension (49% vs 33%), or longer smoking history, among smokers (19 pack years vs 17 pack years). CKD (eGFR<60 mL/min) was associated only with mortality, independent of slope: HR 1.1 (95% CI 1.0-1.3). However, extreme loss in eGFR (>20 mL/min over baseline period) was associated with mortality, independent of baseline eGFR: HR 3.5 (95% CI 2.7-4.4), and also independently associated with composite CVD events and CHF: HR 1.4 and 1.7 (95% CI 1.1-1.9 and 1.2-2.6), respectively.

CONCLUSION

This is the first examination of decline in eGFR in association with mortality and CVD among AIs. The implications of these findings are broad: clinical evaluation may benefit from evaluating change in eGFR over time in addition to dichotomous eGFR. Also, these findings suggest there may be aspects of renal function that are not well-marked by clinical CKD, but which may have particular relevance to long-term renal and vascular health.

American Indian chronic Renal insufficiency cohort study (AI-CRIC study)

BACKGROUND

Chronic kidney disease (CKD) is an increasing epidemic globally that is associated with adverse health outcomes including end stage kidney disease (ESKD), cardiovascular disease (CVD), and death. American Indians (AIs) have a higher prevalence of CKD than most other racial/ethnic groups, due in part to a high prevalence of type 2 diabetes. Other genetic and environmental factors not yet identified may also contribute to the disproportionate burden of CKD in AIs.

METHOD

We will establish 3 clinical centers to recruit AIs from the Southwest United States (US) to expand the Chronic Renal Insufficiency Cohort (CRIC) study. We will follow the current CRIC protocol for kidney and cardiovascular measures and outcomes, which include ambulatory monitoring of kidney function and the use of mobile health technologies for CVD sub-phenotyping, and compare the outcomes in AIs with those in other racial/ethnic groups in CRIC.

DISCUSSION

AI-CRIC will identify the role of various risk factors for rapid loss of kidney function among AIs of the Southwest US. In addition, to better understand the natural history of CKD and CVD in this high-risk population, we will identify unique risk factors for CKD and CVD progression in AIs. We will also compare event rates and risk factors for kidney and cardiovascular events in AIs with the other populations represented in CRIC.

Locus-Specific Differential DNA Methylation and Urinary Arsenic: An Epigenome-Wide Association Study in Blood among Adults with Low-to-Moderate Arsenic Exposure

BACKGROUND

Chronic exposure to arsenic (As), a human toxicant and carcinogen, remains a global public health problem. Health risks persist after As exposure has ended, suggesting epigenetic dysregulation as a mechanistic link between exposure and health outcomes.

OBJECTIVES

We investigated the association between total urinary As and locus-specific DNA methylation in the Strong Heart Study, a cohort of American Indian adults with low-to-moderate As exposure [total urinary As, mean  ( ± SD )  μ g / g creatinine: 11.7 (10.6)].

METHODS

DNA methylation was measured in 2,325 participants using the Illumina MethylationEPIC array. We implemented linear models to test differentially methylated positions (DMPs) and the DMRcate method to identify regions (DMRs) and conducted gene ontology enrichment analysis. Models were adjusted for estimated cell type proportions, age, sex, body mass index, smoking, education, estimated glomerular filtration rate, and study center. Arsenic was measured in urine as the sum of inorganic and methylated species.

RESULTS

In adjusted models, methylation at 20 CpGs was associated with urinary As after false discovery rate (FDR) correction (FDR <   0.05 ). After Bonferroni correction, 5 CpGs remained associated with total urinary As (p Bonferroni < 0.05 ), located in SLC7A11, ANKS3, LINGO3, CSNK1D, ADAMTSL4. We identified one DMR on chromosome 11 (chr11:2,322,050-2,323,247), annotated to C11orf2; TSPAN32 genes.

DISCUSSION

This is one of the first epigenome-wide association studies to investigate As exposure and locus-specific DNA methylation using the Illumina MethylationEPIC array and the largest epigenome-wide study of As exposure. The top DMP was located in SLC7A11A, a gene involved in cystine/glutamate transport and the biosynthesis of glutathione, an antioxidant that may protect against As-induced oxidative stress. Additional DMPs were located in genes associated with tumor development and glucose metabolism. Further research is needed, including research in more diverse populations, to investigate whether As-related DNA methylation signatures are associated with gene expression or may serve as biomarkers of disease development. https://doi.org/10.1289/EHP6263.

Global, regional, and national burden of chronic kidney disease, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017

BACKGROUND

Health system planning requires careful assessment of chronic kidney disease (CKD) epidemiology, but data for morbidity and mortality of this disease are scarce or non-existent in many countries. We estimated the global, regional, and national burden of CKD, as well as the burden of cardiovascular disease and gout attributable to impaired kidney function, for the Global Burden of Diseases, Injuries, and Risk Factors Study 2017. We use the term CKD to refer to the morbidity and mortality that can be directly attributed to all stages of CKD, and we use the term impaired kidney function to refer to the additional risk of CKD from cardiovascular disease and gout.

METHODS

The main data sources we used were published literature, vital registration systems, end-stage kidney disease registries, and household surveys. Estimates of CKD burden were produced using a Cause of Death Ensemble model and a Bayesian meta-regression analytical tool, and included incidence, prevalence, years lived with disability, mortality, years of life lost, and disability-adjusted life-years (DALYs). A comparative risk assessment approach was used to estimate the proportion of cardiovascular diseases and gout burden attributable to impaired kidney function.

FINDINGS

Globally, in 2017, 1·2 million (95% uncertainty interval [UI] 1·2 to 1·3) people died from CKD. The global all-age mortality rate from CKD increased 41·5% (95% UI 35·2 to 46·5) between 1990 and 2017, although there was no significant change in the age-standardised mortality rate (2·8%, -1·5 to 6·3). In 2017, 697·5 million (95% UI 649·2 to 752·0) cases of all-stage CKD were recorded, for a global prevalence of 9·1% (8·5 to 9·8). The global all-age prevalence of CKD increased 29·3% (95% UI 26·4 to 32·6) since 1990, whereas the age-standardised prevalence remained stable (1·2%, -1·1 to 3·5). CKD resulted in 35·8 million (95% UI 33·7 to 38·0) DALYs in 2017, with diabetic nephropathy accounting for almost a third of DALYs. Most of the burden of CKD was concentrated in the three lowest quintiles of Socio-demographic Index (SDI). In several regions, particularly Oceania, sub-Saharan Africa, and Latin America, the burden of CKD was much higher than expected for the level of development, whereas the disease burden in western, eastern, and central sub-Saharan Africa, east Asia, south Asia, central and eastern Europe, Australasia, and western Europe was lower than expected. 1·4 million (95% UI 1·2 to 1·6) cardiovascular disease-related deaths and 25·3 million (22·2 to 28·9) cardiovascular disease DALYs were attributable to impaired kidney function.

INTERPRETATION

Kidney disease has a major effect on global health, both as a direct cause of global morbidity and mortality and as an important risk factor for cardiovascular disease. CKD is largely preventable and treatable and deserves greater attention in global health policy decision making, particularly in locations with low and middle SDI.

FUNDING

Bill & Melinda Gates Foundation.

Association of low-moderate urine arsenic and QT interval: Cross-sectional and longitudinal evidence from the Strong Heart Study

Epidemiologic studies suggest that chronic exposure to arsenic is related to cardiovascular disease (CVD), but the pathophysiological link remains uncertain. We evaluated the association of chronic low-moderate arsenic exposure and arsenic metabolism with baseline difference and annual change in ECG measures (QT interval, JT interval, PR interval, QRS duration, and QT dispersion) using linear mixed models in the Strong Heart Study main cohort (N = 1174, median age 55 years) and family study (N = 1695 diabetes-free, median age 36 years). At baseline, arsenic exposure was measured as the sum of inorganic and methylated species in urine (ΣAs) and arsenic metabolism was measured as the relative percentage of arsenic species. Median ΣAs and Bazett heart rate-corrected QT interval (QTc) were 8.6 μg/g creatinine and 424 ms in the main cohort and 4.3 μg/g and 414 ms in the family study, respectively. In the main cohort, a comparison of the highest to lowest ΣAs quartile (>14.4 vs. <5.2 μg/g creatinine) was associated with a 5.3 (95% CI: 1.2, 9.5) ms higher mean baseline QTc interval but no difference in annual change in QTc interval. In the family study, a comparison of the highest to lowest quartile (>7.1 vs. <2.9 μg/g creatinine) was associated with a 3.2 (95% CI: 0.6, 5.7) ms higher baseline QTc interval and a 0.6 (95% CI: 0.04, 1.2) ms larger annual increase in QTc interval. Associations with JTc interval were similar but stronger in magnitude compared to QTc interval. Arsenic exposure was largely not associated with PR interval, QRS duration or QT dispersion. Similar to arsenic exposure, a pattern of lower %MMA and higher %DMA was associated with longer baseline QTc interval in both cohorts and with a larger annual change in QTc interval in the family study. Chronic low-moderate arsenic exposure and arsenic metabolism were associated with prolonged ventricular repolarization.

The Association of Arsenic Exposure and Arsenic Metabolism With the Metabolic Syndrome and Its Individual Components: Prospective Evidence From the Strong Heart Family Study

Inorganic arsenic exposure is ubiquitous, and both exposure and interindividual differences in its metabolism have been associated with cardiometabolic risk. However, the associations of arsenic exposure and arsenic metabolism with the metabolic syndrome (MetS) and its individual components are relatively unknown. We used Poisson regression with robust variance to evaluate the associations of baseline arsenic exposure (urinary arsenic levels) and metabolism (relative percentage of arsenic species over their sum) with incident MetS and its individual components (elevated waist circumference, elevated triglycerides, reduced high-density lipoprotein cholesterol, hypertension, and elevated fasting plasma glucose) in 1,047 participants from the Strong Heart Family Study, a prospective family-based cohort study in American Indian communities (baseline visits were held in 1998-1999 and 2001-2003, follow-up visits in 2001-2003 and 2006-2009). Over the course of follow-up, 32% of participants developed MetS. An interquartile-range increase in arsenic exposure was associated with a 1.19-fold (95% confidence interval: 1.01, 1.41) greater risk of elevated fasting plasma glucose concentration but not with other individual components of the MetS or MetS overall. Arsenic metabolism, specifically lower percentage of monomethylarsonic acid and higher percentage of dimethylarsinic acid, was associated with higher risk of overall MetS and elevated waist circumference but not with any other MetS component. These findings support the hypothesis that there are contrasting and independent associations of arsenic exposure and arsenic metabolism with metabolic outcomes which may contribute to overall diabetes risk.

Low-moderate urine arsenic and biomarkers of thrombosis and inflammation in the Strong Heart Study

The underlying pathology of arsenic-related cardiovascular disease (CVD) is unknown. Few studies have evaluated pathways through thrombosis and inflammation for arsenic-related CVD, especially at low-moderate arsenic exposure levels (<100 μg/L in drinking water). We evaluated the association of chronic low-moderate arsenic exposure, measured as the sum of inorganic and methylated arsenic species in urine (ΣAs), with plasma biomarkers of thrombosis and inflammation in American Indian adults (45-74 years) in the Strong Heart Study. We evaluated the cross-sectional and longitudinal associations between baseline ΣAs with fibrinogen at three visits (baseline, 1989-91; Visit 2, 1993-95, Visit 3, 1998-99) using mixed models and the associations between baseline ΣAs and Visit 2 plasminogen activator inhibitor-1 (PAI-1) and high sensitivity C-reactive protein (hsCRP) using linear regression. Median (interquartile range) concentrations of baseline ΣAs and fibrinogen, and Visit 2 hsCRP and PAI-1 were 8.4 (5.1, 14.3) μg/g creatinine, 346 (304, 393) mg/dL, 44 (30, 67) mg/L, and 3.8 (2.0, 7.0) ng/mL, respectively. Comparing the difference between the 75th and the 25th percentile of ΣAs (14.3 vs. 5.1 μg/g creatinine), ΣAs was positively associated with baseline fibrinogen among those with diabetes (adjusted geometric mean ratio (GMR): 1.05, 95% CI: 1.02, 1.07) not associated among those without diabetes (GMR: 1.01, 95% CI: 0.99, 1.02) (p-interaction for diabetes = 0.014), inversely associated with PAI-1 (GMR: 0.94, 95% CI: 0.90, 0.99), and not associated with hsCRP (GMR: 1.00, 95% CI: 0.93, 1.08). We found no evidence for an association between baseline ΣAs and annual change in fibrinogen over follow-up (p-interaction = 0.28 and 0.12 for diabetes and non-diabetes, respectively). Low-moderate arsenic exposure was positively associated with baseline fibrinogen in participants with diabetes and unexpectedly inversely associated with PAI-1. Further research should evaluate the role of prothrombotic factors in arsenic-related cardiovascular disease.

Chronic arsenic exposure and risk of carotid artery disease: The Strong Heart Study

BACKGROUND

Inorganic arsenic exposure from naturally contaminated groundwater is related to vascular disease. No prospective studies have evaluated the association between arsenic and carotid atherosclerosis at low-moderate levels. We examined the association of long-term, low-moderate inorganic arsenic exposure with carotid arterial disease.

METHODS

American Indians, 45-74 years old, in Arizona, Oklahoma, and North and South Dakota had arsenic concentrations (sum of inorganic and methylated species, μg/g urine creatinine) measured from baseline urine samples (1989-1991). Carotid artery ultrasound was performed in 1998-1999. Vascular disease was assessed by the carotid intima media thickness (CIMT), the presence of atherosclerotic plaque in the carotid, and by the number of segments containing plaque (plaque score).

RESULTS

2402 participants (mean age 55.3 years, 63.1% female, mean body mass index 31.0kg/m², diabetes 45.7%, hypertension 34.2%) had a median (interquintile range) urine arsenic concentration of 9.2 (5.00, 17.06) µg/g creatinine. The mean CIMT was 0.75mm. 64.7% had carotid artery plaque (3% with >50% stenosis). In fully adjusted models comparing participants in the 80th vs. 20th percentile in arsenic concentrations, the mean difference in CIMT was 0.01 (95% confidence interval (95%CI): 0.00, 0.02) mm, the relative risk of plaque presence was 1.04 (95%CI: 0.99, 1.09), and the geometric mean ratio of plaque score was 1.05 (95%CI: 1.01, 1.09).

CONCLUSIONS

Urine arsenic was positively associated with CIMT and increased plaque score later in life although the association was small. The relationship between urinary arsenic and the presence of plaque was not statistically significant when adjusted for other risk factors. Arsenic exposure may play a role in increasing the severity of carotid vascular disease.

Risk Factors and Prediction of Stroke in a Population with High Prevalence of Diabetes: The Strong Heart Study

BACKGROUND AND OBJECTIVE

American Indians have a high prevalence of diabetes and higher incidence of stroke than that of whites and blacks in the U.S. Stroke risk prediction models based on data from American Indians would be of clinical and public health value.

METHODS AND RESULTS

A total of 3483 (2043 women) Strong Heart Study participants free of stroke at baseline were followed from 1989 to 2010 for incident stroke. Overall, 297 stroke cases (179 women) were identified. Cox models with stroke-free time and risk factors recorded at baseline were used to develop stroke risk prediction models. Assessment of the developed stroke risk prediction models regarding discrimination and calibration was performed by an analogous C-statistic (C) and a version of the Hosmer-Lemeshow statistic (HL), respectively, and validated internally through use of Bootstrapping methods.

RESULTS

Age, smoking status, alcohol consumption, waist circumference, hypertension status, an-tihypertensive therapy, fasting plasma glucose, diabetes medications, high/low density lipoproteins, urinary albumin/creatinine ratio, history of coronary heart disease/heart failure, atrial fibrillation, or Left ventricular hypertrophy, and parental history of stroke were identified as the significant optimal risk factors for incident stroke.

DISCUSSION

The models produced a C = 0.761 and HL = 4.668 (p = 0.792) for women, and a C = 0.765 and HL = 9.171 (p = 0.328) for men, showing good discrimination and calibration.

CONCLUSIONS

Our stroke risk prediction models provide a mechanism for stroke risk assessment designed for American Indians. The models may be also useful to other populations with high prevalence of obesity and/or diabetes for screening individuals for risk of incident stroke and designing prevention programs.

Arsenic metabolism and one-carbon metabolism at low-moderate arsenic exposure: Evidence from the Strong Heart Study

B-vitamins involved in one-carbon metabolism (OCM) can affect arsenic metabolism efficiency in highly arsenic exposed, undernourished populations. We evaluated whether dietary intake of OCM nutrients (including vitamins B2, B6, folate (B9), and B12) was associated with arsenic metabolism in a more nourished population exposed to lower arsenic than previously studied. Dietary intake of OCM nutrients and urine arsenic was evaluated in 405 participants from the Strong Heart Study. Arsenic exposure was measured as the sum of iAs, monomethylarsonate (MMA) and dimethylarsenate (DMA) in urine. Arsenic metabolism was measured as the individual percentages of each metabolite over their sum (iAs%, MMA%, DMA%). In adjusted models, increasing intake of vitamins B2 and B6 was associated with modest but significant decreases in iAs% and MMA% and increases in DMA%. A significant interaction was found between high folate and B6 with enhanced arsenic metabolism efficiency. Our findings suggest OCM nutrients may influence arsenic metabolism in populations with moderate arsenic exposure. Stronger and independent associations were observed with B2 and B6, vitamins previously understudied in relation to arsenic. Research is needed to evaluate whether targeting B-vitamin intake can serve as a strategy for the prevention of arsenic-related health effects at low-moderate arsenic exposure.

Triglyceride and HDL-C Dyslipidemia and Risks of Coronary Heart Disease and Ischemic Stroke by Glycemic Dysregulation Status: The Strong Heart Study

OBJECTIVE

High triglyceride (TG) levels and low HDL cholesterol (HDL-C) levels are risk factors for cardiovascular disease. It is unclear whether this relationship depends on glycemic dysregulation, sex, or LDL cholesterol (LDL-C) level.

RESEARCH DESIGN AND METHODS

We studied 3,216 participants (40% men, 41% with diabetes) who were free of cardiovascular disease at baseline in a community-based, prospective cohort of American Indians (median follow-up 17.7 years). Cox models estimated hazard ratios (HRs) and 95% CIs for incident ischemic stroke and coronary heart disease (CHD) in relation to combined TG and HDL-C status, where a fasting TG level ≥150 mg/dL was "high" and a fasting HDL-C level <40 mg/dL for men (<50 mg/dL for women) was "low." Models included age, sex, BMI, smoking, diabetes, fasting LDL-C level, antihypertensive medications, physical activity, estimated glomerular filtration rate, and urinary albumin-to-creatinine ratio.

RESULTS

Participants with high TG and low HDL levels had a 1.32-fold greater HR (95% CI 1.06-1.64) for CHD than those with normal TG and normal HDL levels. It was observed in participants with diabetes, but not in those without diabetes, that high TG plus low HDL levels were associated with a 1.54-fold greater HR (95% CI 1.15-2.06) for CHD (P value for interaction = 0.003) and a 2.13-fold greater HR (95% CI 1.06-4.29) for stroke (P value for interaction = 0.060). High TG and low HDL level was associated with CHD risk in participants with an LDL-C level of ≥130 mg/dL, but this was not observed in those participants with lower LDL-C levels. Sex did not appear to modify these associations.

CONCLUSIONS

Adults with both high TG and low HDL-C, particularly those with diabetes, have increased risks of incident CHD and stroke. In particular, those with an LDL-C level ≥130 mg/dL may have an increased risk of incident stroke.

Renal Impairment and Cardiovascular Disease in HIV-Positive Individuals: The D:A:D Study

BACKGROUND

While the association between renal impairment and cardiovascular disease (CVD) is well established in the general population, the association remains poorly understood in human immunodeficiency virus (HIV)-positive individuals.

METHODS

Individuals with ≥2 estimated glomerular filtration rate (eGFR) measurements after 1 February 2004 were followed until CVD, death, last visit plus 6 months, or 1 February 2015. CVD was defined as the occurrence of centrally validated myocardial infarction, stroke, invasive cardiovascular procedures, or sudden cardiac death.

RESULTS

During a median follow-up duration of 8.0 years (interquartile range, 5.4-8.9 years) 1357 of 35 357 individuals developed CVD (incidence rate, 5.2 cases/1000 person-years [95% confidence interval {CI}, 5.0-5.5]). Confirmed baseline eGFR and CVD were closely related with 1.8% of individuals (95% CI, 1.6%-2.0%) with an eGFR > 90 mL/minute/1.73 m(2) estimated to develop CVD at 5 years, increasing to 21.1% (95% CI, 6.6%-35.6%) among those with an eGFR ≤ 30 mL/minute/1.73 m(2) The strong univariate relationship between low current eGFR and CVD was primarily explained by increasing age in adjusted analyses, although all eGFRs ≤ 80 mL/minute/1.73 m(2) remained associated with 30%-40% increased CVD rates, and particularly high CVD rates among individuals with an eGFR ≤ 30 mL/minute/1.73 m(2) (incidence rate ratio, 3.08 [95% CI, 2.04-4.65]).

CONCLUSIONS

Among HIV-positive individuals in a large contemporary cohort, a strong relation between confirmed impaired eGFR and CVD was observed. This finding highlights the need for renal preventive measures and intensified monitoring for emerging CVD, particularly in older individuals with continuously low eGFRs.

The association of urine arsenic with prevalent and incident chronic kidney disease: evidence from the Strong Heart Study

BACKGROUND

Few studies have evaluated associations between low to moderate arsenic levels and chronic kidney disease (CKD). The objective was to evaluate the associations of inorganic arsenic exposure with prevalent and incident CKD in American Indian adults.

METHODS

We evaluated the associations of inorganic arsenic exposure with CKD in American Indians who participated in the Strong Heart Study in 3,851 adults ages 45-74 years in a cross-sectional analysis, and 3,119 adults with follow-up data in a prospective analysis. Inorganic arsenic, monomethylarsonate, and dimethylarsinate were measured in urine at baseline. CKD was defined as estimated glomerular filtration rate ≤ 60 ml/min/1.73 m, kidney transplant or dialysis.

RESULTS

CKD prevalence was 10.3%. The median (IQR) concentration of inorganic plus methylated arsenic species (total arsenic) in urine was 9.7 (5.8, 15.7) μg/L. The adjusted odds ratio (OR; 95% confidence interval) of prevalent CKD for an interquartile range in total arsenic was 0.7 (0.6, 0.8), mostly due to an inverse association with inorganic arsenic (OR: 0.4 [0.3, 0.4]). Monomethylarsonate and dimethylarsinate were positively associated with prevalent CKD after adjustment for inorganic arsenic (OR: 3.8 and 1.8). The adjusted hazard ratio of incident CKD for an IQR in sum of inorganic and methylated arsenic was 1.2 (1.03, 1.41). The corresponding HRs for inorganic arsenic, monomethylarsonate, and dimethylarsinate were 1.0 (0.9, 1.2), 1.2 (1.00, 1.3), and 1.2 (1.0, 1.4).

CONCLUSIONS

The inverse association of urine inorganic arsenic with prevalent CKD suggests that kidney disease affects excretion of inorganic arsenic. Arsenic species were positively associated with incident CKD. Studies with repeated measures are needed to further characterize the relation between arsenic and kidney disease development.

Genetics of kidney disease and related cardiometabolic phenotypes in Zuni Indians: the Zuni Kidney Project

The objective of this study is to identify genetic factors associated with chronic kidney disease (CKD) and related cardiometabolic phenotypes among participants of the Genetics of Kidney Disease in Zuni Indians study. The study was conducted as a community-based participatory research project in the Zuni Indians, a small endogamous tribe in rural New Mexico. We recruited 998 members from 28 extended multigenerational families, ascertained through probands with CKD who had at least one sibling with CKD. We used the Illumina Infinium Human1M-Duo version 3.0 BeadChips to type 1.1 million single nucleotide polymorphisms (SNPs). Prevalence estimates for CKD, hyperuricemia, diabetes, and hypertension were 24%, 30%, 17% and 34%, respectively. We found a significant (p < 1.58 × 10^-7) association for a SNP in a novel gene for serum creatinine (PTPLAD2). We replicated significant associations for genes with serum uric acid (SLC2A9), triglyceride levels (APOA1, BUD13, ZNF259), and total cholesterol (PVRL2). We found novel suggestive associations (p < 1.58 × 10^-6) for SNPs in genes with systolic (OLFML2B), and diastolic blood pressure (NFIA). We identified a series of genes associated with CKD and related cardiometabolic phenotypes among Zuni Indians, a population with a high prevalence of kidney disease. Illuminating genetic variations that modulate the risk for these disorders may ultimately provide a basis for novel preventive strategies and therapeutic interventions.

Comparison of estimated GFR equations based on serum cystatin C alone and in combination with serum creatinine in patients with coronary artery disease

OBJECTIVE

Several new equations (GFRCKD-EPI-cr, GFRCKD-EPI-CysC, GFRCKD-EPI Cr+CysC) are used for the calculation of estimated GFR (eGFR) to evaluate renal function. These equations explicitly demonstrate the association of coronary artery disease (CAD) and severe renal impairment cases. However, these equations are considered insufficient to explain the relation with normal or mildly impaired eGFR and CAD. Our hypothesis was to indicate the inversely proportional relationship of eGFR values, calculated by the different equations, with the presence of CAD in patients with normal or mildly impaired renal function.

METHODS

Eighty-eight patients who underwent elective coronary angiographic intervention were enrolled into the study. The study population was divided into two groups based on angiographic documents: patients with normal coronary arteries (CAD-) and patients with CAD (CAD +). These patients were stable and decided to implement angiography for the purpose of suspicion about CAD and control. Since it is thought that eGFR equations based on creatinine are inadequate to determine chronic kidney disease (CKD) and overestimate CKD diagnosis, cystatin C-based equations are considered an alternative. Due to the potential effects of inflammatory events of the markers used in equations, patients with diabetes mellitus, severe CKD, and inflammatory bowel disease were excluded from the study.

RESULTS

The average age of all participants was 51.93±9.31 (32-65 years); 80.7% (n=71) was male. A statistical difference was found between the CAD (-) group and the CAD (+) group in terms of the variables of age (45.46±8.48 vs. 54.95±8.11, p<0.001), gender (67.9% vs. 86.7%, male, p=0.037), cystatin C values (1.37±0.34 vs. 0.85±0.39, p<0.001), and GFR equations defined by the Chronic Kidney Disease Epidemiology: GFRCKD-EPI-cr (85.86±14.20 vs. 79.45±10.25, p=0.018), GFRCKD-EPI-CysC (58.61±21.87 vs. 100.82±32.00, p<0.001), and GFRCKD-EPI Cr+CysC (68.29±13.49 vs. 90.75±18.34, p<0.001). After adjustment of the variables in multiple regression analyses, only age (OR, 1.199; 95% CI, 1.077 to 1.335, p=0.001), gender (OR, 8.252; 95% CI, 0.223 to 55.659, p=0.030), and the GFRCKD-EPI-CysC equation (OR, 1.059; 95% CI, 1.028 to 1.090, p<0.001) were detected as predictors for presence of CAD.

CONCLUSION

GFR equations based on cystatin C or combined with creatinine may have superiority to GFR equations based on creatinine alone in CAD patients. However, the impact of different variables on the GFRCKD-EPI-CysC equation should not be ignored in specific groups, such as CAD.

Replication of the effect of SLC2A9 genetic variation on serum uric acid levels in American Indians

Increased serum uric acid (SUA) or hyperuricemia, a risk factor for gout, renal and cardiovascular diseases, is caused by either increased production or decreased excretion of uric acid or a mix of both. The solute carrier protein 2 family, member 9 (SLC2A9) gene encodes a transporter that mediates urate flux across the renal proximal tubule. Genome-wide association studies have consistently shown the association of single-nucleotide polymorphisms in this gene with SUA in majority populations. American Indian participants of the Strong Heart Family Study, belonging to multigenerational families, have high prevalence of hyperuricemia. We conducted measured genotype analyses, based on variance components decomposition method and accounting for family relationships, to assess whether the association between SUA and SLC2A9 gene polymorphisms generalized to American Indians (n=3604) of this study. Seven polymorphisms were selected for genotyping based on their association with SUA levels in other populations. A strong association was found between SLC2A9 gene polymorphisms and SUA in all centers combined (P-values: 1.3 × 10(-31)-5.1 × 10(-23)) and also when stratified by recruitment center; P-values: 1.2 × 10(-14)-1.0 × 10(-5). These polymorphisms were also associated with the estimated glomerular filtration rate and serum creatinine but not albumin-creatinine ratio. In summary, the association of polymorphisms in the uric acid transporter gene with SUA levels extends to a new population of American Indians.

Raising awareness of acute kidney injury: a global perspective of a silent killer

Worldwide, acute kidney injury (AKI) is associated with poor patient outcomes. Over the last few years, collaborative efforts, enabled by a common definition of AKI, have provided a description of the epidemiology, natural history, and outcomes of this disease and improved our understanding of the pathophysiology. There is increased recognition that AKI is encountered in multiple settings and in all age groups, and that its course and outcomes are influenced by the severity and duration of the event. The effect of AKI on an individual patient and the resulting societal burden that ensues from the long-term effects of the disease, including development of chronic kidney disease (CKD) and end-stage renal disease (ESRD), is attracting increasing scrutiny. There is evidence of marked variation in the management of AKI, which is, to a large extent, due to a lack of awareness and an absence of standards for prevention, early recognition, and intervention. These emerging data point to an urgent need for a global effort to highlight that AKI is preventable, its course is modifiable, and its treatment can improve outcomes. In this article, we provide a framework of reference and propose specific strategies to raise awareness of AKI globally, with the goal to ultimately improve outcomes from this devastating disease.

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.