Low potassium excretion but not high sodium excretion is associated with increased risk of developing chronic kidney disease

Higher potassium intake is associated with a lower risk of chronic kidney disease: population-based prospective study

BACKGROUND

High-potassium intake is associated with a lower risk of cardiovascular disease. However, the association between potassium intake and the development of chronic kidney disease (CKD) remains unclear.

OBJECTIVE

The objective of this study was to investigate whether potassium intake is associated with outcomes of incident CKD.

METHODS

This is a population-based prospective observational cohort study from the UK Biobank cohort between 2006 and 2010. We included 317,162 participants without CKD from the UK Biobank cohort. The main predictor was spot urine potassium-to-creatinine ratio (KCR). The primary outcome was incident CKD, which was defined by the International Classification of Disease 10 codes or Operating Procedure Codes Supplement 4 codes.

RESULTS

At baseline, individuals with higher KCR had lower blood pressure, body mass index, and inflammation, and were less likely to have diabetes and hypertension. During a median follow-up of 11.9 y, primary outcome events occurred in 15,246 (4.8%) participants. In the cause-specific model, the adjusted hazard ratio (aHR) per 1-standard deviation increase in KCR for incident CKD was 0.90 [95% confidence interval (CI): 0.89, 0.92]. Compared with quartile 1 of KCR, the aHRs (95% CIs) for quartiles 2-4 were 0.98 (0.94, 1.02), 0.90 (0.86, 0.95), and 0.80 (0.76, 0.84), respectively. In sensitivity analysis with different definitions of CKD, the results were similar. In addition, further analysis with dietary potassium intake also showed a negatively graded association with the primary outcome.

CONCLUSIONS

Higher urinary potassium excretion and intake were associated with a lower risk of incident CKD.

Association of urinary calcium excretion with chronic kidney disease in patients with type 2 diabetes

PURPOSE

Herein, we investigated the correlation between urinary calcium excretion (UCaE) and chronic kidney disease (CKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

From August 2018 to January 2023, a total of 2031 T2DM patients providing 24-h urine samples were included in the final analyses. Patients were separated into four cohorts, based on the UCaE quartiles. We then analyzed renal functional indicators like estimated glomerular filtration rate (eGFR) and urinary albumin excretion (UAE) among the four groups. Lastly, we utilized multivariable logistic regression models to investigate the correlation between UCaE and CKD.

RESULTS

After adjusting for confounding factors, we observed a decreasing trend in CKD prevalence (36.3%, 13.0%, 7.5%, and 6.6%, respectively, P < 0.001) across the UCaE quartiles. Albuminuria (55.5% vs. 40.0%, 36.5%, 37.4%) and macroalbuminuria prevalence (20.0% vs. 9.3%, 5.2%, 5.7%) in the lowest quartile were markedly elevated, compared to the remaining three quartiles (P < 0.001). Meanwhile, the eGFR level (P < 0.001) showed a clearly increasing trend across the UCaE quartiles, and patients with moderate-to-severe decreases in eGFR levels (with cutoff limits at 30-59, 15-30, and < 15 mL/min/1.73m2) were mostly found in the lowest quartile (P < 0.001). Logistic regression analysis revealed that patients in the lowest quartile experienced an enhanced prevalence of CKD, relative to those in the highest quartile (odds ratio: 5.90, 95% confidence interval: 3.60-9.67, P < 0.001).

CONCLUSION

Decreased UCaE was independently associated with the CKD prevalence in T2DM patients.

Urinary Na/K ratio is a predictor of developing chronic kidney disease in the general population

Chronic kidney disease (CKD) is a major risk factor for cardiovascular diseases as well as end-stage kidney disease. Increased dietary sodium (Na) or decreased dietary potassium (K) deteriorates kidney function; however, findings regarding the association of dietary Na/K ratio with kidney function are limited and conflicting. Therefore, the present study investigated the impact of urinary Na/K ratio on the development of CKD, defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, in the Japanese general population. In total, 14,549 subjects without CKD who participated in our medical checkup were enrolled. The urinary Na/K ratio was measured using a sample of overnight urine. The subjects were followed up until the endpoint (onset of CKD). During the median follow-up period of 61.4 months, CKD developed in 2096 participants (25.9 per 1000 person-years). The risk of developing CKD increased across the quartiles of baseline urinary Na/K ratio in the Kaplan-Meier analysis (log-rank, P < 0.001). In multivariate Cox proportional hazard regression analysis, urinary Na/K ratio was a significant predictor of new-onset CKD after adjustment for important factors including eGFR at baseline (hazard ratio, 2.013; 95% confidence interval, 1.658-2.445; p < 0.001). Moreover, baseline urinary Na/K ratio was found to be independently correlated with yearly decline in eGFR. Similar results were obtained in subgroups of participants with and without hypertension. Thus, urinary Na/K ratio is significantly associated with the development of CKD in the general population.

Self-Reported Frequency of Adding Salt to Food and Risk of Incident Chronic Kidney Disease

Importance

The self-reported frequency of adding salt to foods could reflect a person's long-term salt taste preference, and salt intake has been associated with increased risk of cardiovascular diseases (CVD). Whether self-reported adding of salt to foods is associated with increased risk of chronic kidney disease (CKD) remains unknown.

Objective

To prospectively examine the association of self-reported frequency of adding salt to foods with incident CKD risk in a general population of adults.

Design, Setting, and Participants

This population-based cohort study evaluated UK Biobank participants aged 37 to 73 years who were free of CKD at baseline. Participants were enrolled from 2006 to 2010 and prospectively followed up for disease diagnosis. Data were analyzed from October 2022 to April 2023.

Exposure

Self-reported frequency of adding salt to foods, categorized into never or rarely, sometimes, usually, and always.

Main Outcome and Measure

Incident CKD cases were defined by diagnostic codes. Hazard ratios (HRs) and 95% CIs were calculated by using Cox proportional hazards models. Models were adjusted for several potential confounders including age, sex, race and ethnicity, Townsend Deprivation Index, estimated glomerular filtration rate (eGFR), body mass index, (BMI), smoking status, alcohol drinking status, regular physical activity, high cholesterol, diabetes, CVD, hypertension, infectious disease, immune disease, and nephrotoxic drugs use at baseline.

Results

Within a cohort of 465 288 individuals (mean [SD] age 56.32 [8.08] years; 255 102 female participants [54.83%]; 210 186 male participants [45.17%]), participants with higher self-reported frequency of adding salt to foods were more likely to have a higher BMI, higher Townsend Deprivation Index score, and diminished baseline eGFR compared with those who reported a lower frequency of adding salt to foods. Participants who added salt to their foods were also more likely than those who did not add salt to their foods to be current smokers and have diabetes or CVD at baseline. During a median (IQR) follow-up of 11.8 (1.4) years, 22 031 incident events of CKD were documented. Higher self-reported frequency of adding salt to foods was significantly associated with a higher CKD risk after adjustment for covariates. Compared with those who reported never or rarely adding salt to foods, those who reported sometimes adding salt to food (adjusted HR [aHR], 1.04; 95% CI, 1.00-1.07), those who reported usually adding salt to food (aHR, 1.07; 95% CI, 1.02-1.11), and those who reported always adding salt to food (aHR, 1.11; 95% CI, 1.05-1.18) had an increased risk of CKD (P for trend < .001). In addition, eGFR, BMI, and physical activity significantly modified the associations, which were more pronounced among participants with a higher eGFR, lower BMI, or lower level of physical activity.

Conclusions and Relevance

In this cohort study of 465 288 individuals, a higher self-reported frequency of adding salt to foods was associated with a higher risk of CKD in the general population. These findings suggest that reducing the frequency of adding salt to foods at the table might be a valuable strategy to lower CKD risk in the general population.

Urinary albumin excretion and cancer risk: the PREVEND cohort study

BACKGROUND

Chronic kidney disease (CKD) is believed to be associated with an increased risk for cancer, especially urinary tract cancer. However, previous studies predominantly focused on the association of decreased estimated glomerular filtration rate (eGFR) with cancer. In this study, we investigated the association of albuminuria with cancer incidence, adjusted for eGFR.

METHODS

We included 8490 subjects in the Prevention of Renal and Vascular End-stage Disease (PREVEND) observational study. Urinary albumin excretion (UAE) was measured in two 24-hour urine specimens at baseline. Primary outcomes were the incidence of overall and urinary tract cancer. Secondary outcomes were the incidence of other site-specific cancers, and mortality due to overall, urinary tract, and other site-specific cancers.

RESULTS

Median baseline UAE was 9.4 (IQR, 6.3-17.8) mg/24 h. During a median follow-up of 17.7 years, 1341 subjects developed cancer (of which 177 were urinary tract cancers). After multivariable adjustment including eGFR, every doubling of UAE was associated with a 6% (hazard ratios (HR), 1.06, 95% confidence intervals (CI), 1.02-1.10), and 14% (HR, 1.14, 95% CI, 1.04-1.24) higher risk of overall and urinary tract cancer incidence, respectively. Except for lung and hematological cancer, no associations were found between UAE and the incidence of other site-specific cancer. Doubling of UAE was also associated with a higher risk of mortality due to overall and lung cancer.

CONCLUSIONS

Higher albuminuria is associated with a higher incidence of overall, urinary tract, lung, and hematological cancer, and with a higher risk of mortality due to overall and lung cancers, independent of baseline eGFR.

Estimated 24-h urinary sodium excretion and risk of end-stage kidney disease

The association between sodium intake and long-term kidney disease endpoints is debated and yet to be proven. We aimed to investigate the associations of estimated 24-h urinary sodium excretion, reflecting daily sodium intake, with the incidence of end-stage kidney disease (ESKD). In this prospective cohort study including 444,375 UK Biobank participant, 865 (0.2%) ESKD events occurred after median follow-up of 12.7 years. For every 1 g increment in estimated 24-h urinary sodium excretion, multivariable-adjusted hazard ratio for incident ESKD was 1.09 (95% confidence interval 0.94-1.26). Nonlinear associations were not detected with restricted cubic splines. The null findings were confirmed by a series of sensitivity analyses, which attenuated potential bias from measurement errors of the exposure, regression dilution, reverse causality, and competing risks. In conclusion, there is insufficient evidence that estimated 24-h urinary sodium excretion is associated with the incidence of ESKD.

Proteinuria Modifies the Relationship Between Urinary Sodium Excretion and Adverse Kidney Outcomes: Findings From KNOW-CKD

Introduction

High sodium intake is associated with increased proteinuria. Herein, we investigated whether proteinuria could modify the association between urinary sodium excretion and adverse kidney outcomes in patients with chronic kidney disease (CKD).

Methods

In this prospective observational cohort study, we included 967 participants with CKD stages G1 to G5 between 2011 and 2016, who measured 24-hour urinary sodium and protein excretion at baseline. The main predictors were urinary sodium and protein excretion levels. The primary outcome was CKD progression, which was defined as a ≥50% decline in the estimated glomerular filtration rate (eGFR) or the onset of kidney replacement therapy.

Results

During a median follow-up period of 4.1 years, the primary outcome events occurred in 287 participants (29.7%). There was a significant interaction between proteinuria and sodium excretion for the primary outcome (P = 0.006). In patients with proteinuria of <0.5 g/d, sodium excretion was not associated with the primary outcome. However, in patients with proteinuria of ≥0.5 g/d, a 1.0 g/d increase in sodium excretion was associated with a 29% higher risk of adverse kidney outcomes. Moreover, in patients with proteinuria of ≥0.5 g/d, the hazard ratios (HRs) (95% confidence intervals[CIs]) for sodium excretion of <3.4 and ≥3.4 g/d were 2.32 (1.50-3.58) and 5.71 (3.58-9.11), respectively, compared with HRs for patients with proteinuria of <0.5 g/d and sodium excretion of <3.4 g/d. In sensitivity analysis with 2 averaged values of sodium and protein excretion at baseline and third year, the results were similar.

Conclusion

Higher urinary sodium excretion was more strongly associated with an increased risk of adverse kidney outcomes in patients with higher proteinuria levels.

Rationale and Design of the Diet, CKD, and Apolipoprotein L1 Study in Low-Income and Middle-Income Countries

Introduction

Diet, chronic kidney disease (CKD), and Apolipoprotein L1 (APOL1) (DCA) Study is examining the role of dietary factors in CKD progression and APOL1 nephropathy. We describe enrollment and retention efforts and highlight facilitators and barriers to enrollment and operational challenges, as well as accommodations made in the study protocol.

Methods

The DCA study is enrolling participants in 7 centers in West Africa. Participants who consented were invited to complete dietary recalls and 24-hour urine collections in year 1. We conducted focus groups and semistructured interviews among study personnel to identify facilitators and barriers to enrollment as well as retention and operational challenges in the execution of the study protocol. We analyzed emerging themes using content analyses.

Results

A total of 712 participants were enrolled in 18 months with 1256 24-hour urine and 1260 dietary recalls. Barriers to enrollment were the following: (i) a lack of understanding of research, (ii) the burden of research visits, and (iii) incorporating cultural and traditional nuances when designing research protocols. Factors facilitating enrollment were the following: (i) designing convenient research visits, (ii) building rapport and increased communication between the research team and participants, and (iii) cultural sensitivity - adapting research protocols for the populations involved. Offering home visits, providing free dietary counseling, reducing the volume of study blood collection, and reducing the frequency of visits were some changes made in the study protocol that increased participant satisfaction.

Conclusion

Adopting a participant-centered approach with accommodations in the protocol for cultural adaptability and incorporating participant feedback is vital for carrying out research in low-income and middle-income regions.

Association Between Dietary Potassium Intake Estimated From Multiple 24-Hour Urine Collections and Serum Potassium in Patients With CKD

Introduction

Limited and inconclusive evidence for the association of dietary potassium intake with serum potassium in chronic kidney disease (CKD) patients have been shown, though restricting dietary potassium has been recommended for CKD patients to prevent hyperkalemia. Multiple 24-hour urine collections are necessary to adequately assess potassium intake. We investigated associations of 24-hour urinary potassium excretion (UKV) with serum potassium in CKD outpatients based on multiple 24-hour urine collections.

Methods

This retrospective cohort study was based on outpatients with CKD stages G3 to G5, median age of 72.0 years; and median follow-up of 3.9 months and 8.9 months, respectively, for analyses using 3-time measurement (N = 290 and 870 observations) and 7-time measurements (N = 220 and 1540 observations). The outcome was serum potassium.

Results

Multivariable-adjusted mean difference in serum potassium (mEq/l) and odds ratio of hyperkalemia per 10 mEq/d increase in UKV were, respectively, 0.12 (95% confidence interval [CI]: 0.09-0.15) and 2.15 (1.70-2.73) in generalized estimating equations (GEEs) with 3-time measurements. The mean difference became more pronounced as CKD stages progressed: 0.08 (0.05-0.12), 0.12 (0.08-0.16), and 0.16 (0.12-0.20) for CKD G3, G4, and G5. Similar results were obtained from analyses using 7-time measurements and hierarchical Bayesian measurement error models treating measurement error of UKV adequately.

Conclusion

We suggest significant but weak associations (R²: 0.08, 0.14, and 0.18 for CKD G3, G4, and G5) between serum potassium and dietary potassium intake estimated by multiple 24-hour urine collections in CKD patients. Further studies are needed to validate nutritional and clinical aspects of the associations.

A New Understanding of Potassium's Influence Upon Human Health and Renal Physiology

Potassium channels are expressed in virtually all cell types, and their activity is the dominant determinant of cellular membrane potential. As such, potassium flux is a key regulator of many cellular processes including the regulation of action potentials in excitable cells. Subtle changes in extracellular potassium can initiate signaling processes vital for survival (insulin signaling) while more extreme and chronic changes may lead to pathological states (acid-base disturbances and cardiac arrhythmia). While many factors acutely influence extracellular potassium levels, it is principally the role of the kidneys to maintain potassium balance by matching urinary excretion with dietary intake. When this balance is disrupted, human health is negatively impacted. In this review, we discuss evolving views of dietary potassium intake as means of preventing and mitigating diseases. We also provide an update on a molecular pathway called the potassium switch, a mechanism by which extracellular potassium regulates distal nephron sodium reabsorption. Finally, we review recent literature describing how several popular therapeutics influence potassium homeostasis.

Prognostic Implications of Urinary Potassium to Creatinine Ratio in Patients With Predialysis Chronic Kidney Disease: A Cohort Study

OBJECTIVES

Although a low or high serum potassium level in chronic kidney disease (CKD) is associated with worsening renal function and increased cardiovascular disease (CVD) events, urinary potassium excretion has been found to predict adverse health outcomes with conflicting results. We conducted a cohort study to determine whether urinary potassium to creatinine (K/Cr) ratio is an independent risk for further deterioration in renal function or increased CVD events.

METHODS

We identified 650 predialysis patients with CKD hospitalized for an educational program regarding CKD between January 2010 and December 2018. The study outcomes were CKD progression and incident CVD events, with baseline urinary K/Cr ratio categorized into quartiles-Q1, < 19.8; Q2, 19.9-27.7; Q3, 27.8-37.9; and Q4, > 38.0.

RESULTS

During follow-up (median, 35 months), 509 CKD progressions and 129 incident CVD events were identified. Sixty two patients died during follow-up. Multivariate Cox proportional hazard model showed that after adjustment for demographic factors and laboratory data, patients in Q1 had a 2.02-fold higher risk of worsening renal function than those in Q4 (95% confidence interval, 1.50-2.71; P < .001), whereas urinary K/Cr ratio had no association with the incidence of CVD events. Similarly, inverse probability weighting analysis showed an increased risk of CKD progression in the lowest quartile. Furthermore, the association between low fractional excretion of potassium and worsening renal function was confirmed.

CONCLUSION

A low urinary K/Cr ratio is independently associated with worsening renal function but not with a risk of incident CVD event in predialysis patients with CKD.

Association of 24-h urinary sodium excretion with microalbuminuria in a Chinese population

To assess the relationship of sodium, potassium and the ratio of sodium to potassium (Na/K) with albuminuria, a cross-sectional study was carried out in China in 2017. Sodium, potassium and albumin excretions were examined in a 24-h (h) urine sample collected from 1486 participants. Microalbuminuria was defined as 24-h urinary albumin excretion between 30 and 300 mg/24 h. The participants had an average age of 46.2 ± 14.1 years old, and 48.9% were men. The proportion of patients with microalbuminuria was 9.0%. As illustrated by the adjusted generalized linear mixed model, sodium concentration increased significantly with the increase in 24-h urinary albumin (β = 1.16, 95% confidence interval (CI) 0.38-1.93; P = 0.003). Multivariable-adjusted logistic regression analyses demonstrated that the odds ratio (OR) of microalbuminuria increased with the quartiles of sodium [OR = 2.20, 95% CI 1.26-3.84 (the maximum quartile vs. the minimum quartile), P_{for trend} = 0.006]. Potassium and the Na/K ratio did not have any association with outcome indicators. A high amount of sodium intake was potentially correlated with early renal function impairment.

Urinary Sodium-to-Potassium Ratio and Incident Chronic Kidney Disease: Results From the Korean Genome and Epidemiology Study

OBJECTIVE

To evaluate the association of sodium-potassium intake balance on kidney function.

PATIENTS AND METHODS

Data from the Korean Genome and Epidemiology Study were used. The participants were enrolled between June 1, 2001, and January 31, 2003, and were followed-up until December 31, 2016. The 24-hour excretion levels of sodium and potassium were calculated using the Kawasaki formula with spot urinary potassium and sodium measurements. Participants were categorized into tertiles according to the estimated 24-hour urinary sodium-to-potassium (Na/K) ratio. The primary outcome was incident chronic kidney disease (CKD), defined as an estimated glomerular filtration rate of <60 mL/min per 1.73 m² in two or more consecutive measurements during the follow-up period.

RESULTS

This study included 4088 participants with normal kidney function. The mean age was 52.4±8.9 years, and 1747 (42.7%) were men. The median estimated 24-hour urinary sodium excretion level, potassium excretion level, and Na/K ratio (inter quartile range) were 4.9 (4.1-5.8) g/d, 2.1 (1.8-2.5) g/d, and 2.3 (1.9-2.7) g/d, respectively. During 37,950 person-years of follow-up (median, 11.5 years), 532 participants developed CKD, and the corresponding incidence rate was 14.0 (95% CI, 12.9-15.3) per 1000 person-years. Multivariable Cox hazard analysis revealed that the risk of incident CKD was significantly lower in the lowest tertile than in the highest tertile (HR, 0.78; 95% CI, 0.63-0.97). However, no significant association was found with incident CKD risk when urinary excretion levels of sodium or potassium were evaluated individually.

CONCLUSION

A low urinary Na/K ratio may relate with lower CKD development risk in adults with preserved kidney function.

Apolipoprotein L1 Genotypes and the Association of Urinary Potassium Excretion with CKD Progression

BACKGROUND AND OBJECTIVES

Progressive CKD in Black individuals is strongly associated with polymorphisms in the APOL1 gene, but it is unknown whether dietary risk factors for CKD progression vary in high- versus low-risk APOL1 genotypes. We investigated if APOL1 genotypes modify associations of dietary potassium and sodium with CKD progression and death.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We analyzed 1399 self-identified Black participants enrolled in the Chronic Renal Insufficiency Cohort from April 2003 to September 2008. Exposures were calibrated 24-hour urine potassium and sodium excretion. The primary outcome was CKD progression defined as the time to 50% decline in eGFR or kidney failure. The secondary outcome was CKD progression or death. We tested for an interaction between urinary potassium and sodium excretion and APOL1 genotypes.

RESULTS

Median 24-hour urinary sodium and potassium excretions in Black participants were 150 mmol (interquartile range, 118-188) and 43 mmol (interquartile range, 35-54), respectively. Individuals with high- and low-risk APOL1 genotypes numbered 276 (20%) and 1104 (79%), respectively. After a median follow-up of 5.23 years, CKD progression events equaled 605, and after 7.29 years, CKD progression and death events equaled 868. There was significant interaction between APOL1 genotypes and urinary potassium excretion with CKD progression and CKD progression or death (P=0.003 and P=0.03, respectively). In those with high-risk APOL1 genotypes, higher urinary potassium excretion was associated with a lower risk of CKD progression (quartiles 2-4 versus 1: hazard ratio, 0.83; 95% confidence interval, 0.50 to 1.39; hazard ratio, 0.54; 95% confidence interval, 0.31 to 0.93; and hazard ratio, 0.50; 95% confidence interval, 0.27 to 0.93, respectively). In the low-risk APOL1 genotypes, higher urinary potassium excretion was associated with a higher risk of CKD progression (quartiles 2-4 versus 1: hazard ratio, 1.01; 95% confidence interval, 0.75 to 1.36; hazard ratio, 1.23; 95% confidence interval, 0.91 to 1.66; and hazard ratio, 1.53; 95% confidence interval, 1.12 to 2.09, respectively). We found no interaction between APOL1 genotypes and urinary sodium excretion with CKD outcomes.

CONCLUSIONS

Higher urinary potassium excretion was associated with lower versus higher risk of CKD progression in APOL1 high-risk and low-risk genotypes, respectively.

Urinary Potassium Excretion and Progression From Advanced CKD to Kidney Failure

Background:

Increased dietary potassium intake has well-proven beneficial effects on cardiovascular health and mortality. However, the association between dietary potassium intake and chronic kidney disease (CKD) progression remains unclear with prior studies reporting conflicting results.

Objective:

To study the association between 24-hour urinary potassium excretion (a surrogate for dietary potassium intake) and progression to kidney failure.

Design:

Retrospective cohort study.

Setting:

Ottawa, Canada

Patients:

Patients with advanced CKD referred to the Ottawa Hospital Multi-Care Kidney Clinic from 2010 to 2020.

Measurements:

Twenty-four-hour urinary potassium excretion measured upon referral to the Ottawa Hospital Multi-Care Kidney Clinic as part of routine clinic protocol.

Methods:

Multivariable Cox and Fine and Gray models provided hazard ratios (HRs) and 95% confidence intervals (CIs) to estimate the association between quartiles of 24-hour urinary potassium excretion and progression to kidney failure. A restricted cubic spline analysis examined the possible nonlinear relationship between 24-hour urinary potassium excretion (as a continuous variable) and progression to kidney failure.

Results:

Overall, 432/695 (62%) patients progressed to kidney failure. Across all models, there was no significant difference in kidney failure risk by quartile of 24-hour urinary potassium excretion (all P values for trend ≥.05). Hazard ratios (95% CIs) from the multivariable-adjusted Cox model were as follows: quartile 1, referent; quartile 2, 0.95 (0.71-1.27); quartile 3, 1.00 (0.76-1.33); and quartile 4 0.85 (0.63-1.14); P value for trend = .36. Restricted cubic spline analysis showed an overall linear and nonsignificant relationship between 24-hour urinary potassium excretion as a continuous variable and progression to kidney failure.

Limitations:

Observational design, single center.

Conclusions:

We found no association between 24-hour urinary potassium excretion and progression to kidney failure in patients with advanced CKD. Therefore, we identified no clear evidence that increasing or decreasing dietary potassium intake significantly associates with CKD progression in this population.

Trial Registration:

Not registered.

Insufficient Fruit and Vegetable Intake and Low Potassium Intake Aggravate Early Renal Damage in Children: A Longitudinal Study

Insufficient fruit and vegetable intake (FVI) and low potassium intake are associated with many non-communicable diseases, but the association with early renal damage in children is uncertain. We aimed to identify the associations of early renal damage with insufficient FVI and daily potassium intake in a general pediatric population. We conducted four waves of urine assays based on our child cohort (PROC) study from October 2018 to November 2019 in Beijing, China. We investigated FVI and other lifestyle status via questionnaire surveys and measured urinary potassium, β2-microglobulin (β2-MG), and microalbumin (MA) excretion to assess daily potassium intake and renal damage among 1914 primary school children. The prevalence of insufficient FVI (<4/d) was 48.6% (95% CI: 46.4%, 50.9%) and the estimated potassium intake at baseline was 1.63 ± 0.48 g/d. Short sleep duration, long screen time, lower estimated potassium intake, higher β2-MG and MA excretion were significantly more frequent in the insufficient FVI group. We generated linear mixed effects models and observed the bivariate associations of urinary β2-MG and MA excretion with insufficient FVI (β = 0.012, 95% CI: 0.005, 0.020; β = 0.717, 95% CI: 0.075, 1.359), and estimated potassium intake (β = −0.042, 95% CI: −0.052, −0.033; β = −1.778, 95% CI: −2.600, −0.956), respectively; after adjusting for age, sex, BMI, SBP, sleep duration, screen time and physical activity. In multivariate models, we observed that urinary β2-MG excretion increased with insufficient FVI (β = 0.011, 95% CI: 0.004, 0.018) and insufficient potassium intake (<1.5 g/d) (β = 0.031, 95% CI: 0.023, 0.038); and urinary MA excretion increased with insufficient FVI (β = 0.658, 95% CI: 0.017, 1.299) and insufficient potassium intake (β = 1.185, 95% CI: 0.492, 1.878). We visualized different quartiles of potassium intake showing different renal damage with insufficient FVI for interpretation and validation of the findings. Insufficient FVI and low potassium intake aggravate early renal damage in children and underscores that healthy lifestyles, especially adequate FVI, should be advocated.

A multiple 24-hour urine collection study indicates that kidney function decline is related to urinary sodium and potassium excretion in patients with chronic kidney disease

Multiple 24-hour urine collections are necessary to adequately assess sodium and potassium intake. Here, we assessed kidney function decline for four years after baseline in relation to seven-time averaged 24-hour urinary sodium and potassium excretion (UNaV, UKV), their UNaV/UKV ratio, and their categorical combination in outpatients with chronic kidney disease (CKD). This retrospective cohort study was based on 240 outpatients with baseline CKD stages 3-5, baseline age 20 years or more (median age 72.0 years), and a median follow-up (with interquartile range) of 2.9 (1.4-4.0) years. Outcome was the percentage change in annual slope of estimated glomerular filtration rate (delta eGFR per year). In linear mixed models, percentage changes in delta eGFR per year were -3.26% (95% confidence interval -5.85 to -0.60), +5.20% (2.34 to 8.14), and -5.20% (-7.64 to -2.69), respectively, per one standard deviation increase in the seven-time averaged UNaV and UKV, and their UNaV/UKV ratio. Additionally, percentage changes per year in delta eGFR per year were -16.27% (-23.57 to -8.27) in the middle-to-high UNaV and low UKV group, compared with the low UNaV and middle-to high UKV group. Thus, our study reinforces the observation of opposite associations between GFR decline and urinary excretion rates of sodium (positive) and potassium (negative), respectively. Whether changes in dietary sodium and potassium intake slow GFR decline still requires further study.

Association between the urinary sodium-to-potassium ratio and renal outcomes in patients with chronic kidney disease: a prospective cohort study

A higher urinary sodium-to-potassium (UNa/K) ratio has been reported to be associated with high blood pressure and subsequent cardiovascular events. However, the association between the UNa/K ratio and renal outcomes remains uncertain. We prospectively investigated the association between the UNa/K ratio and renal outcomes in patients with chronic kidney disease (CKD). We enrolled 716 patients with CKD, and 24-h urinary sodium and potassium excretion were measured. Patients were divided into UNa/K ratio tertiles (T1-T3). Endpoints were defined as a composite of doubling of serum creatinine (SCr), end-stage kidney disease (ESKD), or death and a composite of doubling of SCr or ESKD (added as an alternative outcome). We investigated the association between the UNa/K ratio and renal outcomes using a Cox proportional hazards model. During a median follow-up of 2.3 years, doubling of SCr, ESKD, or death and doubling of SCr or ESKD occurred in 332 and 293 patients, respectively. After adjustment for covariates including potentially confounding variables such as plasma renin activity, plasma aldosterone concentration, and B-type natriuretic peptide, the hazard ratios (HRs) (95% confidence intervals [CIs]) for the composite of doubling of SCr, ESKD, or death for T2 and T3 were 1.44 (1.06-1.96) and 1.59 (1.14-2.21), respectively, compared with T1. Additionally, compared with T1, the highest tertile (T3) of the UNa/K ratio was associated with a composite of doubling of SCr or ESKD (HR 1.55, 95% CI 1.09-2.20). A higher UNa/K ratio was independently associated with poor renal outcomes in patients with CKD.

Association of Sodium, Potassium and Sodium-to-Potassium Ratio with Urine Albumin Excretion among the General Chinese Population

Mixed evidence was published regarding the association of sodium, potassium and sodium-to-potassium ratio (Na/K ratio) with renal function impairment. This study was conducted to further explore the relationship between sodium, potassium, NA/K ratio and kidney function in the general adult Chinese population. We performed a cross-sectional analysis using the baseline data from the Action on Salt China (ASC) study. 5185 eligible general adult participants from the baseline investigation of the ASC study were included in this analysis. Sodium, potassium and albumin excretion were examined from 24-h urine collection. Albuminuria was defined as albumin excretion rate (AER) greater than or equal to 30 mg/24-h. Mixed linear regression models, adjusted for confounders, were fitted to analyze the association between sodium, potassium and Na/K ratio, and natural log transformed AER. Mixed effects logistic regression models were performed to analyze the odds ratio of albuminuria at each quintile of sodium, potassium and Na/K ratio. The mean age of the participants was 49.5 ± 12.8 years, and 48.2% were male. The proportion of albuminuria was 7.5%.The adjusted mixed linear models indicated that sodium and Na/K ratio was positively associated with natural log transformed AER (Sodium: β = 0.069, 95%CI [0.050, 0.087], p < 0.001; Na/K ratio: β = 0.026, 95%CI [0.012, 0.040], p < 0.001). Mixed effects logistic regression models showed that the odds of albuminuria significantly increased with the quintiles of sodium (p < 0.001) and Na/K ratio (p = 0.001). No significant association was found between potassium and the outcome indicators. Higher sodium intake and higher Na/K ratio are associated with early renal function impairment, while potassium intake was not associated with kidney function measured by albumin excretion.

Low adherence to CKD-specific dietary recommendations associates with impaired kidney function, dyslipidemia, and inflammation

BACKGROUND/OBJECTIVES

A diet following chronic kidney disease (CKD)-specific recommendations is considered essential for optimal management of patients with CKD. However, data on the adherence to these recommendations and its implications for health-relevant biomarkers are lacking. The objectives were to estimate adherence to CKD-specific dietary recommendations, to identify characteristics and lifestyle variables associated with poor adherence, and to investigate the relationship of adherence with biomarkers.

METHODS

In this cross-sectional analysis, average dietary intake was estimated in 3193 participants with moderately severe CKD enrolled into the observational multicenter German CKD study using a food frequency questionnaire. A CKD diet score was developed to assess adherence to CKD-specific dietary recommendations based on intake of sodium, potassium, fiber, protein, sugar, and cholesterol. The associations of dietary adherence with characteristics, lifestyle variables, and biomarker levels were determined.

RESULTS

Logistic regression analysis revealed younger age, higher body mass index, male gender, lower educational attainment, various lifestyle variables (cigarette smoking, infrequent alcohol consumption, low physical activity), and lower estimated glomerular filtrate rate associated with lower adherence to dietary recommendations. Low adherence to dietary recommendations was further associated with dyslipidemia, higher uric acid, and C-reactive protein levels. Associations between low dietary adherence and biomarkers were mostly driven by low intake of fiber and potassium, and high intake of sugar and cholesterol.

CONCLUSIONS

This study revealed differential characteristics and biomarkers associated with lower adherence to CKD-specific dietary recommendations. Promotion of CKD-specific dietary recommendations may help to mitigate the adverse prognosis in CKD patients.

Urinary Potassium and Kidney Function Decline in the Population-Observational Study

Background-Some data suggest favorable effects of a high potassium intake on kidney function. The present population-based study investigated cross-sectional and longitudinal relations of urinary potassium with kidney function. Methods-Study cohort included 2027 Gubbio Study examinees (56.9% women) with age ≥ 18 years at exam-1 and with complete data on selected variables at exam-1 (1983-1985), exam-2 (1989-1992), and exam-3 (2001-2007). Urinary potassium as urinary potassium/creatinine ratio was measured in daytime spot samples at exam-1 and in overnight timed collections at exam-2. Estimated glomerular filtration rate (eGFR) was measured at all exams. Covariates in analyses included demographics, anthropometry, blood pressure, drug treatments, diabetes, smoking, alcohol intake, and urinary markers of dietary sodium and protein. Results-In multivariable regression, urinary potassium/creatinine ratio cross-sectionally related to eGFR neither at exam-1 (standardized coefficient and 95%CI = 0.020 and -0.059/0.019) nor at exam-2 (0.024 and -0.013/0.056). Exam-1 urinary potassium/creatinine ratio related to eGFR change from exam-1 to exam-2 (0.051 and 0.018/0.084). Exam-2 urinary potassium/creatinine ratio related to eGFR change from exam-2 to exam-3 (0.048 and 0.005/0.091). Mean of urinary potassium/creatinine ratio at exam-1 and exam-2 related to eGFR change from exam-1 to exam-3 (0.056 and 0.027/0.087) and to incidence of eGFR < 60 mL/min per 1.73 m² from exam-1 to exam-3 (odds ratio and 95%CI = 0.78 and 0.61/0.98). Conclusion-In the population, urinary potassium did not relate cross-sectionally to eGFR but related to eGFR decline over time. Data support the existence of favorable effects of potassium intake on ageing-associated decline in kidney function.

Estimation of potassium intake: single versus repeated measurements and the associated cardiorenal risk

BACKGROUND

High potassium intake has been associated with lower blood pressure and a lower incidence of chronic kidney disease and cardiovascular events. In cohort studies, potassium intake is often estimated with a single 24-h urine collection. However, this may not represent actual long-term individual intake. We assessed whether a single baseline versus multiple follow-up measurements of 24-h urine potassium excretion results in different estimates of individual potassium intake and different associations between potassium intake and long-term outcome.

METHODS

We performed a retrospective cohort study in outpatient subjects with an estimated glomerular filtration rate >60 mL/min/1.73 m² who had sampled a 24-h urine collection at baseline and had ≥1 collection during a 17-year follow-up. Potassium intake was estimated with a single baseline 24-h urine collection but also during 1-year, 5-year, and 15-year follow-up. We used cox regression analysis to assess the association between cardiorenal outcome and estimated potassium intake.

RESULTS

Average population (n = 541) 24-h potassium excretion was similar at baseline and follow-up but significant individual changes in potassium intake between baseline and follow-up were observed. Forty-four percent of the subjects switched between tertiles of estimated potassium intake when follow-up measurements were used instead of baseline measurements. Hazard ratios for renal and cardiovascular outcomes were 6.9 and 1.7 times higher when follow-up estimates of potassium intake were replaced by baseline estimates.

CONCLUSIONS

Estimated potassium intake and its association with long-term outcome change significantly when multiple follow-ups 24-h urine collections are used for estimation of potassium intake instead of a single baseline measurement.

Potassium

Potassium is an essential nutrient that performs a vital role in cellular functions including maintaining fluid balance and osmolality of cells. Potassium balance is maintained by the kidney and the majority of ingested potassium is excreted in the urine. There is strong evidence of a negative association between dietary potassium and blood pressure, and some evidence (much of it indirect) of negative associations between dietary potassium and cardiovascular disease (particularly stroke and coronary heart disease) and kidney disease (chronic renal failure, and kidney stones). Blood pressure lowering is particularly associated with high potassium and low sodium diets. Important dietary sources of potassium include fruit and vegetables (including rice, potatoes, legumes and wholegrains), dairy products, and animal proteins. Worldwide, diets are low in potassium compared to dietary guidelines. Interventions focused on increasing dietary potassium will have major benefits including improvements in diet, reducing non-communicable disease and enhancing planetary health.

Focus on the Possible Role of Dietary Sodium, Potassium, Phosphate, Magnesium, and Calcium on CKD Progression

The impressive estimated number of chronic kidney disease (CKD) patients in the world justifies any possible effort at implementing preventive measures of disease progression. Renal insufficiency is associated with significant changes in the electrolyte handling and body balance of sodium, potassium, phosphate, magnesium, and calcium, all of which are biologically vital molecules. Dietary habits could contribute significantly to the optimal management of possible derangements. In this review, we examined the available evidence recommending dietary prescriptions for these five elements aiming at reducing CKD progression. Clear evidence that specific dietary prescriptions may halt or reduce CKD progression is lacking. However, some practical recommendations are possible to prescribe the best possible therapy to the individual CKD patient.

Sodium intake and kidney function in the general population: an observational, population-based study

BACKGROUND

The relationships of sodium intake to kidney function within the population have been poorly investigated and are the objective of the study.

METHODS

This observational, population-based, cross-sectional and longitudinal study targeted 4595 adult participants of the Gubbio study with complete data at baseline exam. Of these participants, 3016 participated in the 15-year follow-up (mortality-corrected response rate 78.4%). Baseline measures included sodium:creatinine ratio in timed overnight urine collection, used as an index of sodium intake, together with serum creatinine, sex, age and other variables. Follow-up measures included serum creatinine and other variables. Estimated glomerular filtration rate (eGFR, mL/min/1.73 m2) was calculated using serum creatinine, sex and age and was taken as an index of kidney function.

RESULTS

The study cohort was stratified in sex- and age-controlled quintiles of baseline urine sodium:creatinine ratio. A higher quintile associated with higher baseline eGFR (P < 0.001). In multivariable analysis, the odds ratio (OR) of Stage1 kidney function (eGFR ≥90 mL/min/1.73 m2) was 1.98 times higher in Quintile 5 compared with Quintile 1 [95% confidence interval (CI) 1.50-2.59, P < 0.001]. The time from baseline to follow-up was 14.1 ± 2.5 years. Baseline to follow-up, the eGFR change was more negative along quintiles (P < 0.001). In multivariable analysis, the OR in Quintile 5 compared with Quintile 1 was 2.21 for eGFR decline ≥30% (1.18-4.13, P = 0.001) and 1.38 for worsened stage of kidney function (1.05-1.82, P = 0.006). Findings were consistent within subgroups.

CONCLUSIONS

Within the general population, an index of higher sodium intake associated cross-sectionally with higher kidney function but longitudinally with greater kidney function decline.

Modifiable Lifestyle Factors for Primary Prevention of CKD: A Systematic Review and Meta-Analysis

BACKGROUND

Despite increasing incidence of CKD, no evidence-based lifestyle recommendations for CKD primary prevention apparently exist.

METHODS

To evaluate the consistency of evidence associating modifiable lifestyle factors and CKD incidence, we searched MEDLINE, Embase, CINAHL, and references from eligible studies from database inception through June 2019. We included cohort studies of adults without CKD at baseline that reported lifestyle exposures (diet, physical activity, alcohol consumption, and tobacco smoking). The primary outcome was incident CKD (eGFR<60 ml/min per 1.73 m²). Secondary outcomes included other CKD surrogate measures (RRT, GFR decline, and albuminuria).

RESULTS

We identified 104 studies of 2,755,719 participants with generally a low risk of bias. Higher dietary potassium intake associated with significantly decreased odds of CKD (odds ratio [OR], 0.78; 95% confidence interval [95% CI], 0.65 to 0.94), as did higher vegetable intake (OR, 0.79; 95% CI, 0.70 to 0.90); higher salt intake associated with significantly increased odds of CKD (OR, 1.21; 95% CI, 1.06 to 1.38). Being physically active versus sedentary associated with lower odds of CKD (OR, 0.82; 95% CI, 0.69 to 0.98). Current and former smokers had significantly increased odds of CKD compared with never smokers (OR, 1.18; 95% CI, 1.10 to 1.27). Compared with no consumption, moderate consumption of alcohol associated with reduced risk of CKD (relative risk, 0.86; 95% CI, 0.79 to 0.93). These associations were consistent, but evidence was predominantly of low to very low certainty. Results for secondary outcomes were consistent with the primary finding.

CONCLUSIONS

These findings identify modifiable lifestyle factors that consistently predict the incidence of CKD in the community and may inform both public health recommendations and clinical practice.

Source and Composition in Amino Acid of Dietary Proteins in the Primary Prevention and Treatment of CKD

Nutrition is a cornerstone in the management of chronic kidney disease (CKD). To limit urea generation and accumulation, a global reduction in protein intake is routinely proposed. However, recent evidence has accumulated on the benefits of plant-based diets and plant-derived proteins without a clear understanding of underlying mechanisms. Particularly the roles of some amino acids (AAs) appear to be either deleterious or beneficial on the progression of CKD and its complications. This review outlines recent data on the role of a low protein intake, the plant nature of proteins, and some specific AAs actions on kidney function and metabolic disorders. We will focus on renal hemodynamics, intestinal microbiota, and the production of uremic toxins. Overall, these mechanistic effects are still poorly understood but deserve special attention to understand why low-protein diets provide clinical benefits and to find potential new therapeutic targets in CKD.

Spot Urine Samples to Estimate Na and K Intake in Patients With Chronic Kidney Disease and Healthy Adults: A Secondary Analysis From a Controlled Feeding Study

OBJECTIVE

The objective of this study was to assess the agreement between estimated 24-hour urinary sodium excretion (e24hUNa) and estimated 24-hour urinary potassium excretion (e24hUK), calculated from a spot urine sample using several available equations and actual sodium and potassium intake from a controlled diet in both healthy participants and those with chronic kidney disease (CKD).

DESIGN AND METHODS

This study is a secondary analysis of a controlled feeding study in CKD patients matched to healthy controls. Participants (n = 16) consumed the controlled diet, which provided ∼2400 mg Na/day and ∼3000 mg K/day, for 8 days. On days 7 and 8, participants consumed all meals and collected all urine in an inpatient research setting, and they were discharged on day 9. The day 7 morning spot urine sample was used to calculate e24hUNa and e24hUK, which was compared with known sodium and potassium intake, respectively.

RESULTS

Average e24hUNa from the INTERSALT and Tanaka-Na equations were higher than actual sodium intake by 373 mg and 559 mg, respectively, though the differences were not significant. e24hUNa from the Nerbass-SALTED equation in CKD participants was significantly higher than actual sodium intake by ∼2000 mg (P < .001), though e24hUNa from the Nerbass-RRID equation was not different from intake. e24hUK from the Tanaka-K equation was significantly lower than actual potassium intake (P < .001). For both e24hUNa and e24hUK for all participants, agreement with actual intake was poor, and e24hUNa and e24hUK were not correlated with actual sodium or potassium intake, respectively.

CONCLUSION

e24hUNa and e24hUK are poor indicators of true sodium and potassium intake, respectively, in both healthy and CKD participants. Findings should be confirmed in larger sample sizes with varying levels of dietary sodium and potassium.

Estimation of Sodium and Potassium Intake: Current Limitations and Future Perspectives

Globally, average dietary sodium intake is double the recommended amount, whereas potassium is often consumed in suboptimal amounts. High sodium diets are associated with increased cardiovascular and renal disease risk, while potassium may have protective properties. Consequently, patients at risk of cardiovascular and renal disease are urged to follow these recommendations, but dietary adherence is often low due to high sodium and low potassium content in processed foods. Adequate monitoring of intake is essential to guide dietary advice in clinical practice and can be used to investigate the relationship between intake and health outcomes. Daily sodium and potassium intake is often estimated with 24-h sodium and potassium excretion, but long-term balance studies demonstrate that this method lacks accuracy on an individual level. Dietary assessment tools and spot urine collections also exhibit poor performance when estimating individual sodium and potassium intake. Collection of multiple consecutive 24-h urines increases accuracy, but also patient burden. In this narrative review, we discuss current approaches to estimating dietary sodium and potassium intake. Additionally, we explore alternative methods that may improve test accuracy without increasing burden.

Sodium Intake Is Associated With Renal Resistive Index in an Adult Population-Based Study

Renal resistive index (RRI) has been associated with adverse renal and cardiovascular outcomes. Although traditionally considered a marker of intrinsic renal damage, RRI could also reflect systemic vascular dysfunction. As sodium intake was linked to alterations in vascular properties, we wished to characterize the association of salt consumption with RRI in the general adult population. Participants were recruited in a population-based study in Switzerland. RRI was measured by ultrasound in 3 segmental arteries. Sodium intake (UNa; mmol/24 h) was estimated on 24-hour urine samples. Carotido-femoral pulse wave velocity was obtained by applanation tonometry. Mixed multivariate regression models were used with RRI or pulse wave velocity as independent variables and UNa as dependent variable, adjusting for possible confounders. We included 1002 patients in the analyses with 528 (52.7%) women and mean age of 47.2±17.4. Mean values of UNa and RRI were 141.8±61.1 mmol/24 h and 63.8±5.5%, respectively. In multivariate analysis, UNa was positively associated with RRI (P=0.002) but not with pulse wave velocity (P=0.344). Plasma renin activity and aldosterone did not modify the relationship between UNa and RRI (P=0.087 for interaction). UNa/urinary potassium ratio was positively associated with pulse wave velocity ≥12 m/s (P=0.033). Our results suggest that dietary salt consumption has a direct impact on renal hemodynamic in the adult general population. Alterations in vascular properties likely explain those findings, but inadequate renal vaso-motor response is also possible. Sodium intake could thus potentially be linked to underlying structural systemic damages affecting this population.

Dietary potassium and the kidney: lifesaving physiology

Potassium often has a negative connotation in Nephrology as patients with chronic kidney disease (CKD) are prone to develop hyperkalaemia. Approaches to the management of chronic hyperkalaemia include a low potassium diet or potassium binders. Yet, emerging data indicate that dietary potassium may be beneficial for patients with CKD. Epidemiological studies have shown that a higher urinary potassium excretion (as proxy for higher dietary potassium intake) is associated with lower blood pressure (BP) and lower cardiovascular risk, as well as better kidney outcomes. Considering that the composition of our current diet is characterized by a high sodium and low potassium content, increasing dietary potassium may be equally important as reducing sodium. Recent studies have revealed that dietary potassium modulates the activity of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule (DCT). The DCT acts as a potassium sensor to control the delivery of sodium to the collecting duct, the potassium-secreting portion of the kidney. Physiologically, this allows immediate kaliuresis after a potassium load, and conservation of potassium during potassium deficiency. Clinically, it provides a novel explanation for the inverse relationship between dietary potassium and BP. Moreover, increasing dietary potassium intake can exert BP-independent effects on the kidney by relieving the deleterious effects of a low potassium diet (inflammation, oxidative stress and fibrosis). The aim of this comprehensive review is to link physiology with clinical medicine by proposing that the same mechanisms that allow us to excrete an acute potassium load also protect us from hypertension, cardiovascular disease and CKD.

Dietary Sodium Intake and Health Indicators: A Systematic Review of Published Literature between January 2015 and December 2019

As the science surrounding population sodium reduction evolves, monitoring and evaluating new studies on intake and health can help increase our understanding of the associated benefits and risks. Here we describe a systematic review of recent studies on sodium intake and health, examine the risk of bias (ROB) of selected studies, and provide direction for future research. Seven online databases were searched monthly from January 2015 to December 2019. We selected human studies that met specified population, intervention, comparison, outcome, time, setting/study design (PICOTS) criteria and abstracted attributes related to the study population, design, intervention, exposure, and outcomes, and evaluated ROB for the subset of studies on sodium intake and cardiovascular disease risks or indicators. Of 41,601 abstracts reviewed, 231 studies were identified that met the PICOTS criteria and ROB was assessed for 54 studies. One hundred and fifty-seven (68%) studies were observational and 161 (70%) focused on the general population. Five types of sodium interventions and a variety of urinary and dietary measurement methods were used to establish and quantify sodium intake. Five observational studies used multiple 24-h urine collections to assess sodium intake. Evidence mainly focused on cardiovascular-related indicators (48%) but encompassed an assortment of outcomes. Studies varied in ROB domains and 87% of studies evaluated were missing information on ≥1 domains. Two or more studies on each of 12 outcomes (e.g., cognition) not previously included in systematic reviews and 9 new studies at low ROB suggest the need for ongoing or updated systematic reviews of evidence on sodium intake and health. Summarizing evidence from assessments on sodium and health outcomes was limited by the various methods used to measure sodium intake and outcomes, as well as lack of details related to study design and conduct. In line with research recommendations identified by the National Academies of Science, future research is needed to identify and standardize methods for measuring sodium intake.

Estimated 24 h Urinary Sodium-to-Potassium Ratio Is Related to Renal Function Decline: A 6-Year Cohort Study of Japanese Urban Residents

The effect of the sodium-to-potassium ratio (Na/K) on renal function within the clinically normal range of renal function are limited. We investigated the effects of an estimated 24 h urinary Na/K (e24hUNa/K) on a 6-year renal function decline among 927 urban Japanese community dwellers with no history of cardiovascular diseases and medication for hypertension, diabetes, or dyslipidemia. We partitioned the subjects into quartiles according to the e24hUNa/K. The estimated glomerular filtration rate (eGFR) was calculated using the chronic kidney disease epidemiology collaboration (CKD/EPI) formula and renal function decline was defined as an absolute value at or above the third quartile of the eGFR decline rate. A multivariable logistic regression model was used for estimation. Compared with the first quartile of the e24hUNa/K, multivariable-adjusted odds ratios (ORs) for eGFR decline in the second, third, and fourth quartiles were 0.96 (95% confidence interval: 0.61–1.51), 1.06 (0.67–1.66), and 1.65 (1.06–2.57), respectively. These results were similar when the simple spot urine Na/K ratio was used in place of the e24hUNa/K. Apparently healthy urban residents with an almost within normal range mean baseline eGFR and high e24hUNa/K ratios had an increased risk for a future decline in renal function. Reducing the Na/K ratio may be important in the prevention of chronic kidney disease in its early stage.

Results of the CARDIA study suggest that higher dietary potassium may be kidney protective

The association between dietary sodium and potassium intake with the development of kidney disease remains unclear, particularly among younger individuals. Here, we determined whether dietary sodium and potassium intake are associated with incident chronic kidney disease (CKD) using data from 1,030 adults (age 23-35 in 1990-1991) from the Coronary Artery Risk Development In Young Adults study, based on repeated measurements of estimated glomerular filtration rate (eGFR) and urinary albumin to creatinine ratio (ACR) from 1995 through 2015. Urinary sodium and potassium excretion (mg/day), calculated from three 24-hour urine collections in 1990-1991, were averaged to measure sodium and potassium intake. Serum creatinine was used to calculate eGFR using the CKD EPI equation; spot urine albumin and creatinine were used to calculate ACR, each at five visits from 1995-1996 through 2015-2016. CKD was defined as decreased eGFR (under 60 ml/min/1.73m2) or the development of albuminuria (ACR over 30 mg/g). We used log binomial regression models adjusted for socio-demographic, behavioral, and clinical factors to determine whether sodium and potassium intake were associated with incident CKD (decreased eGFR or developed albuminuria) among those free of CKD in 1995. Dietary sodium intake was not significantly associated with incident CKD. However, every 1,000 mg/day increment of potassium intake in 1990 was significantly associated with a 29% lower risk of incident albuminuria (relative risk 0.71, 95% confidence interval 0.53, 0.95), but not eGFR. Thus, higher dietary potassium intake may protect against the development of kidney damage, particularly albuminuria.

Impact of Dietary Potassium Restrictions in CKD on Clinical Outcomes: Benefits of a Plant-Based Diet

In patients with advanced-stage chronic kidney disease (CKD), progressive kidney function decline leads to increased risk for hyperkalemia (serum potassium > 5.0 or >5.5 mEq/L). Medications such as renin-angiotensin-aldosterone system inhibitors pose an additional hyperkalemia risk, especially in patients with CKD. When hyperkalemia develops, clinicians often recommend a diet that is lower in potassium content. This review discusses the barriers to adherence to a low-potassium diet and the impact of dietary restrictions on adverse clinical outcomes. Accumulating evidence indicates that a diet that incorporates potassium-rich foods has multiple health benefits, which may also be attributable to the other vitamin, mineral, and fiber content of potassium-rich foods. These benefits include blood pressure reductions and reduced risks for cardiovascular disease and stroke. High-potassium foods may also prevent CKD progression and reduce mortality risk in patients with CKD. Adjunctive treatment with the newer potassium-binding agents, patiromer and sodium zirconium cyclosilicate, may allow for optimal renin-angiotensin-aldosterone system inhibitor therapy in patients with CKD and hyperkalemia, potentially making it possible for patients with CKD and hyperkalemia to liberalize their diet. This may allow them the health benefits of a high-potassium diet without the increased risk for hyperkalemia, although further studies are needed.

Increasing potassium intake to prevent kidney damage: a new population strategy?

Reducing dietary sodium consumption and increasing potassium intake are effective approaches in reducing the prevalence of cardiovascular diseases. Whether this is also true for chronic kidney disease (CKD) is still debated. Elfassy et al. have examined associations between urinary sodium and potassium excretion and the incidence of CKD in young, 30-year-old subjects followed for 20 years. Although they failed to find an association between sodium intake and CKD incidence, there was an inverse association between high potassium intake and the development of albuminuria.

Serum Calcification Propensity and the Risk of Cardiovascular and All-Cause Mortality in the General Population: The PREVEND Study

OBJECTIVE

Vascular calcification contributes to the cause of cardiovascular disease. The calciprotein particle maturation time (T₅₀) in serum, a measure of calcification propensity, has been linked with adverse outcomes in patients with chronic kidney disease, but its role in the general population is unclear. We investigated whether serum T₅₀ is associated with cardiovascular mortality in a large general population-based cohort. Approach and Results: The relationship between serum T₅₀ and cardiovascular mortality was studied in 6231 participants of the PREVEND (Prevention of Renal and Vascular End-Stage Disease) cohort. All-cause mortality was the secondary outcome. Mean (±SD) age was 53±12 years, 50% were male, and mean serum T₅₀ was 329±58 minutes. A shorter serum T₅₀ is indicative of a higher calcification propensity. Serum T₅₀ was inversely associated with circulating phosphate, age, estimated glomerular filtration rate, and alcohol consumption, whereas plasma magnesium was positively associated with serum T₅₀ (P<0.001, total multivariable model R²=0.281). During median (interquartile range) follow-up for 8.3 (7.8-8.9) years, 364 patients died (5.8%), of whom 95 (26.1%) died from a cardiovascular cause. In multivariable Cox proportional hazard models, each 60 minutes decrease in serum T₅₀ was independently associated with a higher risk of cardiovascular mortality (fully adjusted hazard ratio [95% CI], 1.22 [1.04-1.36], P=0.021). This association was modified by diabetes mellitus; stratified analysis indicated a more pronounced association in individuals with diabetes mellitus.

CONCLUSIONS

Serum T₅₀ is independently associated with an increased risk of cardiovascular mortality in the general population and thus may be an early and potentially modifiable risk marker for cardiovascular mortality.

Urinary Sodium-to-Potassium Ratio and Blood Pressure in CKD

Introduction

In the general population, urinary sodium-to-potassium (uNa/K) ratio associates more strongly with high blood pressure (BP) than either urinary sodium or potassium alone. Whether this is also the case among patients with chronic kidney disease (CKD) is unknown.

Methods

We studied the associations of spot urine sodium-to-creatinine (uNa/Cr), potassium-to-creatinine (uK/Cr), and uNa/K ratios with a single office BP reading in 1660 patients with moderate to severe CKD at inclusion in the CKD-REIN cohort.

Results

Patients' median age was 68 (interquartile range [IQR], 59-76) years; most were men (65%), had moderate CKD (57%), and albuminuria (72%). Mean systolic and diastolic BP was 142/78 mm Hg. Spot uNa/Cr and uNa/K ratios were positively associated with systolic, mean arterial, and pulse pressures. The mean adjusted difference in systolic BP between the highest and the lowest quartile (Q4 vs. Q1) was 4.24 (95% confidence interval [CI], 1.53-6.96) mm Hg for uNa/Cr and 4.79 (95% CI, 2.18-7.39) mm Hg for uNa/K. Quartiles of spot uK/Cr were not associated with any BP index. The higher the quartile of uNa/K, the higher the prevalence ratio of uncontrolled (Q4 vs. Q1, 1.43; 95% CI, 1.19-1.72) or apparently treatment-resistant hypertension (Q4 vs. Q1, 1.35; 95% CI, 1.14-1.60). Findings were consistent in a subset of 803 individuals with 2 BP readings.

Conclusion

In patients with CKD, higher urinary sodium excretion is associated with higher BP, but unlike in general population, lower potassium excretion is not. Urinary Na/K does not add significant value in assessing high BP risk, except perhaps for hypertension control assessment.

Long-term potassium intake and associated renal and cardiovascular outcomes in the clinical setting

BACKGROUND & AIMS

High potassium intake has been suggested to lower the risk for renal and cardiovascular outcome, but data are conflicting. This may be explained by the use of different methods for potassium intake assessment across studies. Also, most data are limited to the general population. We investigated the optimal potassium intake, as measured with multiple 24-h urine samples, in patients with a clinical indication for 24-h urine collection, for prevention of cardiorenal disease.

METHODS

We performed a retrospective cohort study in 541 outpatient subjects with an estimated glomerular filtration rate >60 mL/min/1.73 m² who had sampled a 24-h urine collection between 1998 and 1999, and had at least 1 additional collection during a 17-year follow-up. We assessed incidence of renal (i.e. renal replacement therapy, 60% decline in estimated glomerular filtration rate or death) and cardiovascular disease (i.e. cardiovascular event or death).

RESULTS

Average age of subjects was 47 years. Estimated mean potassium intake was 74 mmol/day and remained similar during follow-up. The highest tertile of estimated potassium intake was associated with a significant 76% reduction in renal outcome, and 73% decrease of cerebrovascular events, while no effect for overall cardiovascular outcome was found. A 20-mmol increase in potassium intake during follow-up was associated with a 24% reduction in renal outcome.

CONCLUSIONS

Our data demonstrate that high estimated potassium intake is associated with improved renal outcome and less cerebrovascular events in outpatient subjects with preserved kidney function.

NH3 Plasma-Treated Magnesium Doped Zinc Oxide in Biomedical Sensors with Electrolyte-Insulator-Semiconductor (EIS) Structure for Urea and Glucose Applications

This study compared the sensing characteristics of ZnO (ZO) treated with ammonia (NH3) plasma for 1 min, 3 min, and 6 min, under the EIS structure. The measurement results revealed that, after 3 min of NH3 plasma treatment, the Mg-doped ZnO (MZO) sensing film had a high hydrogen ion sensitivity, linearity, hysteresis, and drift rate of 53.82 mV/pH, 99.04%, 2.52 mV, and 1.75 mV/h, respectively. The sensing film was used with sodium and potassium ion solutions, and it performed satisfactorily in sensing hydrogen ions. Additionally, we investigated the biomedical sensing properties of Mg-doped ZnO (MZO) sensing film with regard to urea, creatinine, and glucose solutions and found that the Mg-doped ZnO (MZO) sensing film treated with NH3 plasma for 3 min had the best properties for sensing urea, creatinine, and glucose. Specifically, with glucose, the sensing film achieved the best linearity and sensitivity and of 97.87% and 10.73 mV/mM, respectively. The results revealed that the sensing characteristics varied with the processing environment and are useful in the developing biomedical sensing applications with different sensing elements.

Regulation of the Renal NaCl Cotransporter and Its Role in Potassium Homeostasis

Daily dietary potassium (K+) intake may be as large as the extracellular K+ pool. To avoid acute hyperkalemia, rapid removal of K+ from the extracellular space is essential. This is achieved by translocating K+ into cells and increasing urinary K+ excretion. Emerging data now indicate that the renal thiazide-sensitive NaCl cotransporter (NCC) is critically involved in this homeostatic kaliuretic response. This suggests that the early distal convoluted tubule (DCT) is a K+ sensor that can modify sodium (Na+) delivery to downstream segments to promote or limit K+ secretion. K+ sensing is mediated by the basolateral K+ channels Kir4.1/5.1, a capacity that the DCT likely shares with other nephron segments. Thus, next to K+-induced aldosterone secretion, K+ sensing by renal epithelial cells represents a second feedback mechanism to control K+ balance. NCC’s role in K+ homeostasis has both physiological and pathophysiological implications. During hypovolemia, NCC activation by the renin-angiotensin system stimulates Na+ reabsorption while preventing K+ secretion. Conversely, NCC inactivation by high dietary K+ intake maximizes kaliuresis and limits Na+ retention, despite high aldosterone levels. NCC activation by a low-K+ diet contributes to salt-sensitive hypertension. K+-induced natriuresis through NCC offers a novel explanation for the antihypertensive effects of a high-K+ diet. A possible role for K+ in chronic kidney disease is also emerging, as epidemiological data reveal associations between higher urinary K+ excretion and improved renal outcomes. This comprehensive review will embed these novel insights on NCC regulation into existing concepts of K+ homeostasis in health and disease.

Abnormal circadian rhythm of urinary sodium excretion correlates closely with hypertension and target organ damage in Chinese patients with CKD

Whether the abnormal circadian rhythm of urinary sodium excretion is associated with hypertension in chronic kidney disease (CKD) is poorly understood. In this study, we assessed the relationship between the circadian rhythm of urinary sodium excretion and hypertension. Urinary samples were collected during both the day (07:00 to 22:00) and night (22:00 to 07:00) to estimate night/day urinary sodium excretion ratios. Blood pressure (BP) and clinical data were also measured. A total of 1,099 Chinese CKD patients were recruited, 308 patients were excluded, and 791 patients were final enrolled in this study. Among them, 291 patients were normotensive and 500 were hypertensive CKD patients. A 1:1 propensity score matching (PSM) analysis was performed with age and estimated glomerular filtration rate (eGFR) matched between 190 normotensive and hypertensive patients. In the full cohort and PSM cohort, multivariate regression analysis showed that the night/day urinary sodium excretion ratio was an independent risk factor for clinical hypertension, whereas 24 h urinary sodium excretion, diurnal and nocturnal urinary sodium excretion were not. When the night/day urinary sodium excretion ratios were further divided into tertiles (tertile 1 < 0.47, tertile 2, 0.47-0.84 and tertile 3 > 0.84), multivariate analysis showed that tertile 3 was independently associated with hypertension in the full and PSM cohorts. In addition, tertile 3 was also independently associated with eGFR ≤ 60 mL/min/1.73 m² and left ventricular hypertrophy. These data suggested that an abnormal circadian rhythm of urinary sodium excretion was independently associated with hypertension and target-organ damage. Individualized salt intake and therapeutic strategies should be used to normalize the natriuretic dipping profile in CKD patients.

Urinary Oxalate Excretion and Long-Term Outcomes in Kidney Transplant Recipients

Epidemiologic studies have linked urinary oxalate excretion to risk of chronic kidney disease (CKD) progression and end-stage renal disease. We aimed to investigate whether urinary oxalate, in stable kidney transplant recipients (KTR), is prospectively associated with risk of graft failure. In secondary analyses we evaluated the association with post-transplantation diabetes mellitus, all-cause mortality and specific causes of death. Oxalate excretion was measured in 24-h urine collection samples in a cohort of 683 KTR with a functioning allograft ≥1 year. Mean eGFR was 52 ± 20 mL/min/1.73 m2. Median (interquartile range) urinary oxalate excretion was 505 (347-732) µmol/24-h in women and 519 (396-736) µmol/24-h in men (p = 0.08), with 302 patients (44% of the study population) above normal limits (hyperoxaluria). A consistent and independent inverse association was found with all-cause mortality (HR 0.77, 95% CI 0.63-0.94, p = 0.01). Cause-specific survival analyses showed that this association was mainly driven by an inverse association with mortality due to infection (HR 0.56, 95% CI 0.38-0.83, p = 0.004), which remained materially unchanged after performing sensitivity analyses. Twenty-four-hour urinary oxalate excretion did not associate with risk of graft failure, post-transplant diabetes mellitus, cardiovascular mortality, mortality due to malignancies or mortality due to miscellaneous causes. In conclusion, in KTR, 24-h urinary oxalate excretion is elevated in 44% of KTR and inversely associated with mortality due to infectious causes.

Urinary Potassium Excretion and Progression of CKD

BACKGROUND AND OBJECTIVES

Data on whether low or high urinary potassium excretion is associated with poor kidney outcome have been conflicting. The aim of this study was to clarify the association between urinary potassium excretion and CKD progression.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We investigated the relationship between lower urinary potassium excretion and CKD progression and compared three urinary potassium indices among 1821 patients from the Korean Cohort Study for Outcome in Patients with CKD. Urinary potassium excretion was determined using spot urinary potassium-to-creatinine ratio, spot urinary potassium concentration, and 24-hour urinary potassium excretion. Patients were categorized into four groups according to quartiles of each urinary potassium excretion metric. The study end point was a composite of a ≥50% decrease in eGFR from baseline values and ESKD.

RESULTS

During 5326 person-years of follow-up, the primary outcome occurred in 392 (22%) patients. In a multivariable cause-specific hazard model, lower urinary potassium-to-creatinine ratio was associated with higher risk of CKD progression (adjusted hazard ratio, 1.47; 95% confidence interval, 1.01 to 2.12) comparing the lowest quartile with the highest quartile. Sensitivity analyses with other potassium metrics also showed consistent results in 855 patients who completed 24-hour urinary collections: adjusted hazard ratios comparing the lowest quartile with the highest quartile were 3.05 (95% confidence interval, 1.54 to 6.04) for 24-hour urinary potassium excretion, 1.95 (95% confidence interval, 1.05 to 3.62) for spot urinary potassium-to-creatinine ratio, and 3.79 (95% confidence interval, 1.51 to 9.51) for spot urinary potassium concentration.

CONCLUSIONS

Low urinary potassium excretion is associated with progression of CKD.

Educational level and risk of chronic kidney disease: longitudinal data from the PREVEND study

Background

The longitudinal association between low education and chronic kidney disease (CKD) and its underlying mechanisms is poorly characterized. We therefore examined the association of low education with incident CKD and change in kidney function, and explored potential mediators of this association.

Methods

We analysed data on 6078 participants from the community-based Prevention of Renal and Vascular End-stage Disease study. Educational level was categorized into low, medium and high (&lt; secondary, secondary/equivalent, &gt; secondary schooling, respectively). Kidney function was assessed by estimating glomerular filtration rate (eGFR) by serum creatinine and cystatin C at five examinations during ∼11 years of follow-up. Incident CKD was defined as new-onset eGFR &lt;60 mL/min/1.73 m2 and/or urinary albumin ≥30 mg/24 h in those free of CKD at baseline. We estimated main effects with Cox regression and linear mixed models. In exploratory causal mediation analyses, we examined mediation by several potential risk factors.

Results

Incident CKD was observed in 861 (17%) participants. Lower education was associated with higher rates of incident CKD [low versus high education; hazard ratio (HR) (95% CI) 1.25 (1.05–1.48), Ptrend = 0.009] and accelerated eGFR decline [B (95% CI) −0.15 (−0.21 to −0.09) mL/min/1.73 m2/year, Ptrend &lt; 0.001]. The association between education and incident CKD was mediated by smoking, potassium excretion, body mass index (BMI), waist-to-hip ratio (WHR) and hypertension. Analysis on annual eGFR change in addition suggested mediation by magnesium excretion, protein intake and diabetes.

Conclusions

In the general population, we observed an inverse association of educational level with CKD. Diabetes and the modifiable risk factors smoking, poor diet, BMI, WHR and hypertension are suggested to underlie this association. These findings provide support for targeted preventive policies to reduce socioeconomic disparities in kidney disease.

Effects of Coffee Intake on Incident Chronic Kidney Disease: A Community-Based Prospective Cohort Study

BACKGROUND

Drinking coffee can raise public health problems, but the association between coffee and kidney disease is unknown. We studied whether coffee intake can affect the development of chronic kidney disease in the general population.

METHODS

We analyzed 8717 subjects with normal renal function recruited from the Korean Genome and Epidemiology Study (KoGES) cohort. Based on a food frequency questionnaire, coffee consumption was categorized into 5 groups: 0 per week, <1 cup per week, 1-6 cups per week, 1 cup per day, and ≥2 cups per day. The primary outcome was incident chronic kidney disease, defined as an estimated glomerular filtration rate <60 mL/min/1.73 m².

RESULTS

The mean age (standard deviation) of study subjects was 52.0 (8.8) years, and 47.8% were male. Among the subjects, 52.8% were daily coffee consumers. During a mean follow-up of 11.3 (range, 5.9-11.5) years, 9.5% of participants developed chronic kidney disease. The incident chronic kidney disease occurred less in daily coffee consumers. Unadjusted hazard ratios (HRs) was significantly lower in daily coffee consumers. In multivariable Cox model even after adjustment of blood pressure, hypertension, cardiovascular disease, diabetes, and amount of daily intake for caffeine-containing foods such as tea and chocolate, coffee consumers with 1 cup per day (HR, 0.76; 95% confidence interval, 0.63-0.92) and ≥2 cups per day (HR, 0.80; 95% confidence interval, 0.65-0.98) were associated with a lower risk of chronic kidney disease development than nondrinkers. Time-averaged and time-varying Cox models yielded similar results. The rates of decline in glomerular filtration were lower in daily coffee consumers.

CONCLUSIONS

Our findings suggest that daily coffee intake is associated with decreased risk of the development of chronic kidney disease.