Comparison of Urinary Sodium and Blood Pressure Relationship From the Spot Versus 24-Hour Urine Samples

Associations between estimation of salt intake and salt-restriction spoons and hypertension status in patients with poorly controlled hypertension: a community-based study from Huzhou City, Eastern China

BACKGROUND

As the prevalence of hypertension increases in China, it is advised to use salt-restriction spoons (SRS) as a lifestyle modification. This study aimed to examine the associations between estimated salt consumption, SRS usage, and the hypertension status in individuals with poorly controlled hypertension.

METHODS

Data was collected in Huzhou City, Zhejiang Province, in 2021 using convenience sampling. The analysis involved ordinal logistic regression and restricted cubic splines to assess the relevant factors.

RESULTS

The study found that 73.34% of the 1215 patients had uncontrolled blood pressure (BP). Urinary excretion was assessed through the utilization of the Kawasaki, INTERSALT, and Tanaka formulas. The outcomes of these three methodologies revealed average daily sodium excretion values of 208.70 (65.65), 154.78 (33.91), and 162.61 (40.87) mmol, respectively. The prevalence of utilizing SRS was found to be 37.78% in this study. Despite the acknowledgment among SRS users of the potential hazards associated with excessive salt consumption, there exists a contradictory pattern of attitudes and behaviors concerning salt reduction. Among individuals with different levels of salt intake (quartiles 1-4, Q1 vs Q4), there was a positive association between limiting salt and hypertension status when controlling for other variables (Kawasaki adjusted OR = 0.58, 95% CI = 0.43-0.79; INTERSALT adjusted OR = 0.62, 95% CI = 0.41-0.92; Tanaka adjusted OR = 0.61, 95% CI = 0.45-0.92, p < 0.05). Our research also revealed that using or used SRS was a protective factor for blood BP control (adjusted OR = 0.79, 95% CI = 0.64-0.99, P < 0.05). The restricted cubic spline plots illustrated a monotonic upward relationship between estimated 24-h urinary Na and BP (P-overall association < 0.05; P-non-linear association > 0.05).

CONCLUSIONS

The use of dietary SRS could result in decrease in daily salt intake for BP control in patients with poorly controlled hypertension. To reduce the impact of high BP in China, additional studies are required to create interventions that can enhance the results for patients.

The World Hypertension League Science of Salt: a regularly updated systematic review of salt and health outcomes studies (Sept 2019 to Dec 2020)

The World Hypertension League Science of Salt health outcomes review series highlights high-quality publications relating to salt intake and health outcomes. This review uses a standardised method, outlined in previous reviews and based on methods developed by WHO, to identify and critically appraise published articles on dietary salt intake and health outcomes. We identified 41 articles published between September 2019 to December 2020. Amongst these, two studies met the pre-specified methodological quality criteria for critical appraisal. They were prospective cohort studies and examined physical performance and composite renal outcomes as health outcomes. Both found an association between increased/higher sodium intake and poorer health outcomes. Few studies meet criteria for high-quality methods. This review adds further evidence that dietary salt reduction has health benefits and strengthens evidence relating to health outcomes other than blood pressure and cardiovascular disease. We observe that most studies on dietary sodium do not have adequate methodology to reliably assess sodium intake and its association with health outcomes.

Urinary Sodium Excretion and Obesity Markers among Bangladeshi Adult Population: Pooled Data from Three Cohort Studies

We evaluated the relationship of urinary sodium excretion with a conditional mean, 10th and 90th percentiles of body mass index (BMI), and waist circumference among 10,034 person-visits of Bangladeshi population. We fitted linear mixed models with participant-level random intercept and restricted maximum likelihood estimation for conditional mean models; and quantile mixed-effect models with participant-level random intercept and Laplace estimation for 10th and 90th percentiles models. For each 100 mmol/24 h increase in urinary sodium excretion, participants had a 0.10 kg/m2 (95% CI: 0.00, 0.10) increase in the mean; a 0.39 kg/m2 (95% CI: 0.23, 0.54) increase in the 10th percentile; and a 0.59 kg/m2 (95% CI: 0.39, 0.78) increase in the 90th percentile of BMI. For each 100 mmol/24 h increase in urinary sodium excretion, participants had a 0.20 cm (95% CI: 0.10, 0.30) increase in mean; a 0.18 cm (95% CI: -0.03, 0.40) change in the 10th percentile; and a 0.23 cm (95% CI: 0.03, 0.43) increase in the 90th percentile of waist circumference. We found a modest association between urine sodium and conditional mean of BMI and waist circumference. The magnitude of associations between urine sodium and the 10th and 90th percentile BMI distributions were higher compared to the conditional mean models, suggesting high sodium intake could be more detrimental to underweight and obese participants.

Spot Urine Formulas to Estimate 24-Hour Urinary Sodium Excretion Alter the Dietary Sodium and Blood Pressure Relationship

[Figure: see text].

Guideline-Driven Management of Hypertension: An Evidence-Based Update

Several important findings bearing on the prevention, detection, and management of hypertension have been reported since publication of the 2017 American College of Cardiology/American Heart Association Blood Pressure Guideline. This review summarizes and places in context the results of relevant observational studies, randomized clinical trials, and meta-analyses published between January 2018 and March 2021. Topics covered include blood pressure measurement, patient evaluation for secondary hypertension, cardiovascular disease risk assessment and blood pressure threshold for drug therapy, lifestyle and pharmacological management, treatment target blood pressure goal, management of hypertension in older adults, diabetes, chronic kidney disease, resistant hypertension, and optimization of care using patient, provider, and health system approaches. Presenting new information in each of these areas has the potential to increase hypertension awareness, treatment, and control which remain essential for the prevention of cardiovascular disease and mortality in the future.

At-home determination of 24-h urine sodium excretion: Validation of chloride test strips and multiple spot samples

Sodium intake and compliance with dietary sodium modification are typically assessed using a 24-h urine collection analyzed using flame photometry, but this is inconvenient. Spot urine samples have been investigated as alternatives to 24-h collections, but their accuracy is poor. Since sodium and chloride are present in equal concentrations in dietary salt, chloride test strips may provide a suitable proxy for at-home measurement of urine sodium concentrations. We aimed to determine whether (i) chloride test strips provide a reliable measure of urinary sodium compared to the gold standard flame photometry and (ii) multiple spot samples accurately reflect 24-h urine sodium. We recruited 43 participants (19 males) aged 23.6 ± 0.6 years to complete multiple consecutive spot samples (morning and evening) along with a 24-h urine sodium collection. Urine 24-h sodium estimates using chloride test strips (114.6 ± 7.5 mmol/day) were highly correlated (r = 0.900, p < 0.0001) with flame photometry (121.1 ± 7.7 mmol/day) with a bias of -6.53 ± 22.2 mmol/day. Use of a three-spot sample average (both morning and evening spot samples) with a correction factor applied (122.9 ± 4.1 mmol/day) provided a good approximation of 24-h sodium measured by flame photometry (125.6 ± 9.0 mmol/day), with a bias of -2.55 ± 43.9 mmol/day. Chloride test strips applied to a 24-h urine collection provide a highly accurate measure of urinary sodium excretion, permitting convenient at-home sample collection and analysis. Their application to multiple spot samples provides a reasonable approximation of sodium excretion that can be used to conveniently monitor attempts at dietary sodium manipulation, without the inconvenience of completing a 24-h urine sample.

Salt intake and blood pressure in Iranian children and adolescents: a population-based study

BACKGROUND

Previous studies have reported a high prevalence of hypertension in Iranian students, especially in rural areas. The aim of this study was to investigate the daily intake of salt in students and its association with high blood pressure.

METHODS

A random sub-sample was selected from the participants of the second phase of Shahroud schoolchildren eye cohort study and then a random urine sample was tested for sodium, potassium and creatinine. Urine electrolyte esexcretion and daily salt intake were calculated by Tanaka et al.'s formula.

RESULTS

Among 1455 participants (including 230 participants from rural area and 472 girls), the mean age was 12.9 ± 1.7 year and the mean daily salt intake was 9.7 ± 2.6 g (95% CI 9.5-9.8). The mean salt consumption in rural areas [10.8 (95% CI 10.4-11.2)] was higher than urban areas [9.4 (95% CI 9.3-9.6)], in people with hypertension [10.8 (95% CI 10.3-11.3)] was more than people with normal blood pressure [9.4 (95% CI 9.3-9.6)], and in boys [9.8 (95% CI 9.7-10.0)] was more than girls [9.3 (95% CI 9.1-9.6)]. Higher age, BMI z-score, male sex and rural life, were associated with increased daily salt intake. Increased salt intake was associated with increased systolic and diastolic blood pressure.

CONCLUSION

Daily salt intake in Iranian adolescents was about 2 times the recommended amount of the World Health Organization, was higher in rural areas and was associated with blood pressure. Reducing salt intake should be considered as an important intervention, especially in rural areas.

Urinary Sodium Excretion and Blood Pressure Relationship across Methods of Evaluating the Completeness of 24-h Urine Collections

We compared the sodium intake and systolic blood pressure (SBP) relationship from complete 24-h urine samples determined by several methods: self-reported no-missed urine, creatinine index ≥0.7, measured 24-h urine creatinine (mCER) within 25% and 15% of Kawasaki predicted urine creatinine, and sex-specific mCER ranges (mCER 15-25 mg/kg/24-h for men; 10-20 mg/kg/24-h for women). We pooled 10,031 BP and 24-h urine sodium data from 2143 participants. We implemented multilevel linear models to illustrate the shape of the sodium-BP relationship using the restricted cubic spline (RCS) plots, and to assess the difference in mean SBP for a 100 mmol increase in 24-h urine sodium. The RCS plot illustrated an initial steep positive sodium-SBP relationship for all methods, followed by a less steep positive relationship for self-reported no-missed urine, creatinine index ≥0.7, and sex-specific mCER ranges; and a plateaued relationship for the two Kawasaki methods. Each 100 mmol/24-h increase in urinary sodium was associated with 0.64 (95% CI: 0.34, 0.94) mmHg higher SBP for self-reported no-missed urine, 0.68 (95% CI: 0.27, 1.08) mmHg higher SBP for creatinine index ≥0.7, 0.87 (95% CI: 0.07, 1.67) mmHg higher SBP for mCER within 25% Kawasaki predicted urine creatinine, 0.98 (95% CI: -0.07, 2.02) mmHg change in SBP for mCER within 15% Kawasaki predicted urine creatinine, and 1.96 (95% CI: 0.93, 2.99) mmHg higher SBP for sex-specific mCER ranges. Studies examining 24-h urine sodium in relation to health outcomes will have different results based on how urine collections are deemed as complete.

Past Sodium Intake, Contemporary Sodium Intake, and Cardiometabolic Health in Southwest Coastal Bangladesh

Background We compared the relationship of past and contemporary sodium (Na) intake with cardiometabolic biomarkers. Methods and Results A total of 1191 participants' data from a randomized controlled trial in coastal Bangladesh were analyzed. Participants provided 24-hour urine Na (24UNa) data for 5 monthly visits. Their fasting blood glucose, total cholesterol, triglycerides, high-density lipoprotein, blood pressure, and 24-hour urine protein were measured at the fifth visit. Participants' mean 24UNa over the first 4 visits was the past Na, and 24UNa of the fifth visit was the contemporary Na intake. We estimated the prevalence ratios of elevated cardiometabolic biomarkers and metabolic syndrome across 24UNa tertiles by multilevel logistic regression using participant-, household-, and community-level random intercepts. Models were adjusted for age, sex, body mass index, smoking, physical activity, alcohol consumption, sleep hours, religion, and household wealth. Compared with participants in tertile 1 of past urine Na, those in tertile 3 had 1.46 (95% CI, 1.08-1.99) times higher prevalence of prediabetes or diabetes mellitus, 5.49 (95% CI, 2.73-11.01) times higher prevalence of large waist circumference, and 1.60 (95% CI, 1.04-2.46) times higher prevalence of metabolic syndrome. Compared with participants in tertile 1 of contemporary urine Na, those in tertile 3 had 1.93 (95% CI, 1.24-3.00) times higher prevalence of prediabetes or diabetes mellitus, 3.14 (95% CI, 1.45-6.83) times higher prevalence of proteinuria, and 2.23 (95% CI, 1.34-3.71) times higher prevalence of large waist circumference. Conclusions Both past and contemporary Na intakes were associated with higher cardiometabolic disease risk.

Associations between metabolic syndrome and urinary Na-to-K ratio and glomerular filtration rate in middle-aged adults regardless of Na and K intakes

BACKGROUND

Intake of Na-to-K ratio (I-Na/K), urinary Na-to-K ratio (U-Na/K), and estimated glomerular filtration rate (GFR) have been reported to be risk factors of metabolic syndrome (MetS), but results are inconsistent. We examined the hypothesis that U-Na/K, GFR, and a preference for salty foods are associated with MetS risk and the hypothesis in 8540 adults aged over 40 years without chronic kidney disease.

METHODS

Participants were categorized using a U-Na/K of < 2.1 (low-U-Na/k) and a GFR of < 60 mL/min (low-GFR). A GFR of 60-90 mL/min was considered as a normal level, since it is a normal or marginal disease state. Correlations and associations were determined using Pearson's correlation coefficients and logistic regression analysis after adjusting for covariates related to MetS.

RESULTS

U-Na/K, but not I-Na/K, was positively correlated with blood pressure (r² = 0.20, P < 0.0001). The GFR was negatively correlated with age, gender, HOMA-B, and MetS (r² = - 0.14 to - 0.595, P < 0.0001), and positively correlated with education, current smoking, and alcohol intake (r² = 0.21 to 0.40, P < 0.0001). MetS risk had a positive association with the following combinations with low-U-Na/K + low-GFR, high-U-Na/K + high-GFR, and high-U-Na/K +low-GFR by 1.830-, 3.182-, and 3.696-fold, respectively, as compared with low-U-Na/K + high-GFR. Risks of the MetS components (abdominal obesity, hypertriglyceridemia, hypo-HDL-cholesterolemia, hypertension, and hyperglycemia) were similarly associated with U-Na/K and GFR, though hypertension had the strongest association. Hypertension risk had positive associations with low-U-Na/K + low-GFR, high-U-Na/K + high-GFR, and high-U-Na/K + low-GFR by 1.526-, 14.06-, and 7.079-fold, respectively, as compared with low-U-Na/K + high-GFR.

CONCLUSION

MetS risk was found to be associated with U-Na/K and GFR regardless of I-Na/K. Women need to maintain a high GFR to reduce the MetS risk, especially the risk of hypertension.

Associations of drinking rainwater with macro-mineral intake and cardiometabolic health: a pooled cohort analysis in Bangladesh, 2016-2019

This study explores the associations of drinking rainwater with mineral intake and cardiometabolic health in the Bangladeshi population. We pooled 10030 person-visit data on drinking water sources, blood pressure (BP) and 24-h urine minerals. Fasting blood glucose (FBG) was measured in 3724 person-visits, and lipids in 1118 person-visits. We measured concentrations of sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) in 253 rainwater, 935 groundwater and 130 pond water samples. We used multilevel linear or gamma regression models with participant-, household- and community-level random intercepts to estimate the associations of rainwater consumption with urine minerals and cardiometabolic biomarkers. Rainwater samples had the lowest concentrations of Na, K, Ca and Mg. Rainwater drinkers had lower urine minerals than coastal groundwater drinkers: -13.42 (95% CI: -18.27, -8.57) mmol Na/24 h, -2.00 (95% CI: -3.16, -0.85) mmol K/24 h and -0.57 (95% CI: -1.02, -0.16) mmol Mg/24 h. The ratio of median 24-hour urinary Ca for rainwater versus coastal groundwater drinkers was 0.72 (95% CI: 0.64, 0.80). Rainwater drinkers had 2.15 (95% CI: 1.02, 3.27) mm Hg higher systolic BP, 1.82 (95% CI: 1.19, 2.54) mm Hg higher diastolic BP, 0.59 (95% CI: 0.17, 1.01) mmol/L higher FBG and -2.02 (95% CI: -5.85, 0.81) mg/dl change in high-density lipoprotein cholesterol compared with the coastal groundwater drinkers. Drinking rainwater was associated with worse cardiometabolic health measures, which may be due to the lower intake of salubrious Ca, Mg and K.

Comparison of Urinary Sodium and Blood Pressure Relationship From the Spot Versus 24-Hour Urine Samples

Background We compared the relationship between sodium (Na) intake and blood pressure when Na intake was estimated from first- and second-morning spot urine samples using the INTERSALT (International Study on Salt and Blood Pressure) formula, versus directly measured 24-hour samples. Methods and Results We collected 24-hour urine and first- and second-morning voids of 383 participants in coastal Bangladesh for 2 visits. We measured participants' blood pressure using an Omron® HEM-907 monitor. To assess the shape of the relationship between urinary Na and blood pressure, we created restricted cubic spline plots adjusted for age, sex, body mass index, smoking and alcohol consumption, physical activities, religion, sleep hours, and household wealth. To assess multicollinearity, we reported variance inflation factors, tolerances, and Leamer's and Klein's statistics following linear regression models. The mean daily urinary Na was 122 (SD 26) mmol/d for the first; 122 (SD 27) mmol/d for the second; and 134 (SD 70) mmol/d for the 24-hour samples. The restricted cubic spline plots illustrated no association between first-morning urinary Na and systolic blood pressure until the 90th percentile distribution followed by a downward relationship; a nonlinear inverse-V-shaped relationship between second-morning urinary Na and systolic blood pressure; and a monotonic upward relationship between 24-hour urinary Na and systolic blood pressure. We found no evidence of multicollinearity for the 24-hour urinary Na model. Conclusions The urinary Na and systolic blood pressure relationship varied for 3 urinary Na measurements. Twenty-four-hour urinary Na captured more variability of Na intake compared with spot urine samples, and its regression models were not affected by multicollinearity.