Validity of predictive equations for 24-h urinary sodium excretion at the population and individual levels among Chinese adults aged 18–69 years

AbstractSpot urine (SU) collection is a convenient method commonly used for sodium estimation, but its validity in predicting 24-h urinary sodium (24-hUNa) excretion has not been thoroughly evaluated among the general population. The aim of this study was to comprehensively assess the validity of eight existing methods in predicting 24-hUNa excretion by using SU samples among Chinese adults. We analyzed 1424 representative individuals aged 18 to 69 years. We compared the measured and estimated measurements of 24-hUNa at the population level by examining bias, the correlation, intraclass correlation coefficients (ICCs), receiver operating characteristic (ROC) curves and Bland–Altman plots and analyzed the relative and absolute differences and misclassification at the individual level. The bias for all methods was significant (all p < 0.001), among which the smallest bias was − 7.9 mmol for the Toft formula and the largest bias was − 53.8 mmol for the Mage formula. Correlation coefficients were all less than 0.380, all formulas exhibited an area under the ROC curve below 0.683, and the Bland–Altman plots indicated slightly high dispersion of the estimation biases at higher sodium levels regardless of the formula. The proportions of relative differences > 40% for the eight methods were all over one-third, the proportions of absolute differences > 51.3 mmol/24 h (3 g/day NaCl) were all over 40%, and the misclassification rates (7, 10, and 13 g/day NaCl as cutoff points) were all over 65%. Caution remains due to poor validity between estimated and actual measurements when using the eight formulas to obtain a plausible estimation for surveillance of the Chinese population sodium excretion, and the results do not support the application of SU to estimate sodium intake at the individual level due to its poor performance with respect to classification.

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Abstract MP78: Validity of Predictive Equations for 24-Hour Urine Sodium Excretion in Young Black and Other Adults

Circulation ◽

10.1161/circ.127.suppl_12.amp78 ◽

2013 ◽

Vol 127 (suppl_12) ◽

Author(s):

Mary Cogswell ◽

Chia-Yih Wang ◽

Te-Ching Chen ◽

Christine Pfeiffer ◽

Paul Elliott ◽

...

Keyword(s):

Sodium Excretion ◽

Sodium Intake ◽

Urine Collection ◽

Urine Sodium ◽

Predictive Equations ◽

Spot Urine ◽

Individual Level ◽

Urine Sodium Excretion ◽

Mean Differences ◽

The Individual

Introduction: Reducing mean population sodium intake by ~1200 mg is projected to reduce thousands of deaths from heart disease and stroke and save billions of health care dollars annually. Twenty-four hour urine collection is recommended for assessing changes in mean population sodium intake, but can be difficult to implement. Predicting 24-hour urine sodium excretion using spot urines is not recommended due to diurnal variations in excretion. Further, sodium excretion patterns differ between black and white persons. We assessed the validity of previously published prediction equations for 24-hour sodium excretion in black and other young adults by timing of spot urine collection. Design: Of 481 adult volunteers aged 18-39 years (50% Blacks) asked to participate in a 2011 study in the Metropolitan DC area, 407 collected each urine void in a separate container for 24 hours. Four timed voids from the 24-h urine collection were selected (morning, afternoon, evening, and overnight) to use with previously published predictive equations. Predictive equations were based on one of two approaches; 1) an indirect approach using spot urine sodium-to-creatinine concentrations and predicted 24-hour creatinine excretion ( Tanaka, Kawasaki, Mage ), and 2) a direct approach using spot urine sodium, potassium, and creatinine concentrations, and age, and body mass index with separate equations by sex ( Brown ). We assessed mean differences between predicted and measured 24-hour sodium excretion (bias) and individual differences across levels of sodium excretion using Bland-Altman plots. Results: Among participants, mean measured 24-hour sodium excretion was ~3300 mg (SD ~1400 mg). Of the equations evaluated, mean bias in predicted 24-hour sodium excretion was least from Brown equations when using morning (-165 mg, 95% confidence interval [CI], -295, -36 mg), afternoon (-90 mg, 95% CI, -208, 28 mg) or evening ( -120 mg, 95% CI -230, -11 mg) spot urines. When using overnight spot urines, mean bias from Brown equations was greatest and statistically significant (-247 mg, 95% CI, -348, -151 mg). When using overnight spot urines, mean bias from Tanaka (-23 mg) or Mage (-145 mg) equations was not significant, however, when stratified by sex, mean biases were significant and in opposite directions. Among Blacks, mean biases from Brown were not significant (-167 to 122 mg) except using overnight specimens among Black females (-267 mg, 95% CI, -525, -47 mg). Across equations and time periods, Bland-Altman plots indicated significant bias at the individual level. Conclusions: Of the evaluated equations, predicted 24-hour urine sodium excretion using the Brown equations with morning, afternoon, or evening specimens may provide the least biased estimates of group mean sodium intake among young US adults. None of the equations adequately predicted individual 24-hour sodium excretion measured on the same day.

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Assessment and validation of spot urine in estimating the 24-h urinary sodium, potassium, and sodium/potassium ratio in Chinese adults

Journal of Human Hypertension ◽

10.1038/s41371-019-0274-z ◽

2019 ◽

Vol 34 (2) ◽

pp. 184-192 ◽

Cited By ~ 2

Author(s):

Jianwei Xu ◽

Xiaofu Du ◽

Yamin Bai ◽

Le Fang ◽

Min Liu ◽

...

Keyword(s):

Chinese Population ◽

Pearson Correlation ◽

Intraclass Correlation ◽

Correlation Coefficients ◽

Population Level ◽

Urinary Sodium ◽

Chinese Adults ◽

Sodium Potassium ◽

Spot Urine ◽

Urinary Potassium

Abstract The commonly used methods of estimating the 24-h urinary sodium (UNa) and urinary potassium (UK) from spot urine (SU) are the Kawasaki method (K-method), INTERSALT method (I-method), and Tanaka method (T-method), but the method that is suitable for use in the general Chinese population is still uncertain. We aimed to assess and validate these methods in estimating the 24-h UNa and UK using SU samples in Chinese adults. We studied 1428 individuals aged 18–69 years using SU and 24-h urine samples. For the K-method, I-method, and T-method, the Pearson correlation coefficients of the 24-h UNa were 0.35, 0.35, and 0.33 (all p < 0.01), and the intraclass correlation coefficients (ICC) were 0.34, 0.26, and 0.26 (all p < 0.01), respectively. The estimated 24-h UK using the K-method and T-method had correlation coefficients of 0.36 and 0.39 (all p < 0.01) and ICCs of 0.31 and 0.27 (all p < 0.01). The mean bias for the K-method in estimating the 24-h UNa and UK were the least biased among these methods. The bias between the 24-h urine Na/K ratio and the spot urinary Na/K ratio by the Bland–Altman method was −0.22. These methods for estimating the 24-h UNa and UK from SU were inadequate at the population level in Zhejiang Province, although the K-method showed the least bias among these methods. The spot urine Na/K ratio may be a useful and alternative method for 24-h urine collection for the estimation of the urinary Na/K ratio in the Chinese population.

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Association between 24-h urinary sodium and potassium excretion and blood pressure among Chinese adults aged 18–69 years

Scientific Reports ◽

10.1038/s41598-021-83049-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Xiaofu Du ◽

Le Fang ◽

Jianwei Xu ◽

Xiangyu Chen ◽

Yamin Bai ◽

...

Keyword(s):

Blood Pressure ◽

Sodium Excretion ◽

Sodium Intake ◽

Urinary Sodium Excretion ◽

Urinary Sodium ◽

Inverse Association ◽

Potassium Excretion ◽

Chinese Adults ◽

Potassium Intake ◽

Sodium And Potassium

AbstractThe direction and magnitude of the association between sodium and potassium excretion and blood pressure (BP) may differ depending on the characteristics of the study participant or the intake assessment method. Our objective was to assess the relationship between BP, hypertension and 24-h urinary sodium and potassium excretion among Chinese adults. A total of 1424 provincially representative Chinese residents aged 18 to 69 years participated in a cross-sectional survey in 2017 that included demographic data, physical measurements and 24-h urine collection. In this study, the average 24-h urinary sodium and potassium excretion and sodium-to-potassium ratio were 3811.4 mg/day, 1449.3 mg/day, and 4.9, respectively. After multivariable adjustment, each 1000 mg difference in 24-h urinary sodium excretion was significantly associated with systolic BP (0.64 mm Hg; 95% confidence interval [CI] 0.05–1.24) and diastolic BP (0.45 mm Hg; 95% CI 0.08–0.81), and each 1000 mg difference in 24-h urinary potassium excretion was inversely associated with systolic BP (− 3.07 mm Hg; 95% CI − 4.57 to − 1.57) and diastolic BP (− 0.94 mm Hg; 95% CI − 1.87 to − 0.02). The sodium-to-potassium ratio was significantly associated with systolic BP (0.78 mm Hg; 95% CI 0.42–1.13) and diastolic BP (0.31 mm Hg; 95% CI 0.10–0.53) per 1-unit increase. These associations were mainly driven by the hypertensive group. Those with a sodium intake above about 4900 mg/24 h or with a potassium intake below about 1000 mg/24 h had a higher risk of hypertension. At higher but not lower levels of 24-h urinary sodium excretion, potassium can better blunt the sodium-BP relationship. The adjusted odds ratios (ORs) of hypertension in the highest quartile compared with the lowest quartile of excretion were 0.54 (95% CI 0.35–0.84) for potassium and 1.71 (95% CI 1.16–2.51) for the sodium-to-potassium ratio, while the corresponding OR for sodium was not significant (OR, 1.28; 95% CI 0.83–1.98). Our results showed that the sodium intake was significantly associated with BP among hypertensive patients and the inverse association between potassium intake and BP was stronger and involved a larger fraction of the population, especially those with a potassium intake below 1000 mg/24 h should probably increase their potassium intake.

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Urine Spot Samples Can Be Used to Estimate 24-Hour Urinary Sodium Excretion in Children

Journal of Nutrition ◽

10.1093/jn/nxy211 ◽

2018 ◽

Vol 148 (12) ◽

pp. 1946-1953 ◽

Cited By ~ 6

Author(s):

Magali Rios-Leyvraz ◽

Pascal Bovet ◽

René Tabin ◽

Bernard Genin ◽

Michel Russo ◽

...

Keyword(s):

Sodium Excretion ◽

Salt Intake ◽

Sodium Intake ◽

Population Level ◽

Urinary Sodium Excretion ◽

Cross Sectional Study ◽

Urinary Sodium ◽

Cross Sectional ◽

High Sodium ◽

Individual Level

ABSTRACT Background The gold standard to assess salt intake is 24-h urine collections. Use of a urine spot sample can be a simpler alternative, especially when the goal is to assess sodium intake at the population level. Several equations to estimate 24-h urinary sodium excretion from urine spot samples have been tested in adults, but not in children. Objective The objective of this study was to assess the ability of several equations and urine spot samples to estimate 24-h urinary sodium excretion in children. Methods A cross-sectional study of children between 6 and 16 y of age was conducted. Each child collected one 24-h urine sample and 3 timed urine spot samples, i.e., evening (last void before going to bed), overnight (first void in the morning), and morning (second void in the morning). Eight equations (i.e., Kawasaki, Tanaka, Remer, Mage, Brown with and without potassium, Toft, and Meng) were used to estimate 24-h urinary sodium excretion. The estimates from the different spot samples and equations were compared with the measured excretion through the use of several statistics. Results Among the 101 children recruited, 86 had a complete 24-h urine collection and were included in the analysis (mean age: 10.5 y). The mean measured 24-h urinary sodium excretion was 2.5 g (range: 0.8–6.4 g). The different spot samples and equations provided highly heterogeneous estimates of the 24-h urinary sodium excretion. The overnight spot samples with the Tanaka and Brown equations provided the most accurate estimates (mean bias: −0.20 to −0.12 g; correlation: 0.48–0.53; precision: 69.7–76.5%; sensitivity: 76.9–81.6%; specificity: 66.7%; and misclassification: 23.0–27.7%). The other equations, irrespective of the timing of the spot, provided less accurate estimates. Conclusions Urine spot samples, with selected equations, might provide accurate estimates of the 24-h sodium excretion in children at a population level. At an individual level, they could be used to identify children with high sodium excretion. This study was registered at clinicaltrials.gov as NCT02900261.

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24-Hour vs. Spot Urinary Sodium and Potassium Measurements in Adult Hypertensive Patients: A Cohort Validation Study

American Journal of Hypertension ◽

10.1093/ajh/hpz104 ◽

2019 ◽

Vol 32 (10) ◽

pp. 983-991

Author(s):

Elizabeth R Wan ◽

Jennifer Cross ◽

Reecha Sofat ◽

Stephen B Walsh

Keyword(s):

Sodium Excretion ◽

Sodium Intake ◽

Urinary Sodium Excretion ◽

Sodium Concentration ◽

Serum Biochemistry ◽

Urinary Sodium ◽

Hypertensive Patients ◽

Spot Urine ◽

Sodium Ingestion ◽

Weak Negative Correlation

Abstract BACKGROUND Sodium intake is correlated with the development of hypertension. Guyton’s principals suggest that the 24-hour urinary sodium excretion reflects sodium ingestion over the same period. 24-hour urine collections are arduous to collect, so many centers use spot urinary measurements instead. We compared spot to matched 24-hour urinary electrolyte measurements. METHODS We examined 419 hypertensive patients from the UCL Complex Hypertension Clinic. 77 had matched and complete 24-hour and spot urinary and serum biochemistry to examine. We compared the spot and 24-hour urinary; sodium concentration, Na/Cr ratio, FENa, Kawasaki and Tanaka estimated sodium excretion as well as the potassium concentration, K/Cr ratio, Kawasaki and Tanaka potassium excretion. RESULTS Our cohort was 58% male and the median age was 41 years. The 24-hour and spot Na concentrations correlated moderately (r = 0.4633, P < 0.0001). The 24-hour and spot Na/creatinine ratios correlated weakly (r = 0.2625, P = 0.0194). The 24-hour and spot FENa results showed a weak negative correlation (r = −0.222, P = ns). The 24-hour sodium excretion and the Kawasaki-derived spot urine sodium excretion correlated moderately (r = 0.3118, P = 0.0052). All Bland–Altman analyses showed poor agreement. The 24-hour and spot potassium concentrations correlated very poorly (r = 0.1158, P = ns). The 24-hour and spot urinary K/creatinine ratios correlated weakly (r = 0.47, P ≤ 0.0001). 24-hour and Kawasaki and Tanaka estimated potassium excretions correlated much better (r = 0.58, P < 0.0001). CONCLUSIONS Spot urinary measurements of sodium give a very poor understanding of the natriuresis occurring over the same 24-hour period. The Kawasaki and Tanaka estimations of the 24-hour sodium excretion showed a much lower correlation than previously reported.

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Is the urinary iodine/Creatinine ratio applicable to assess individual iodine status in Chinese adults? Comparison of iodine estimates from 24-hour urine and timed-spot urine samples in different periods of the day

10.21203/rs.3.rs-940158/v1 ◽

2021 ◽

Author(s):

Zhuan Liu ◽

Yixuan Lin ◽

Jiani Wu ◽

Diqun Chen ◽

Xiaoyan Wu ◽

...

Keyword(s):

Urinary Iodine ◽

Iodine Concentration ◽

Urinary Iodine Excretion ◽

Urinary Iodine Concentration ◽

Prediction Equations ◽

Chinese Adults ◽

Iodine Status ◽

Spot Urine ◽

Individual Level ◽

The Individual

Abstract Background: Urinary iodine concentration (UIC) is routinely used to evaluate the population iodine status while the uniform method for the individual level assessment is uncertain. Objectives : To explore the 24-hour urinary iodine excretion (UIE) in five different periods of the day and the corresponding prediction equations respect by the use of creatinine-corrected UIC. Methods: We collected 24-hour, spot and fasting urine in five periods of the day to estimate 24-hour UIE by the six different prediction equations. We compared the estimated creatinine-corrected UIC to the collected 24-hour UIE and identified the most suitable equations in each period of the day. Results: Among the six different prediction equations, the equation of Kawasaki T was the best to estimate the 24-hour UIE by fasting urine among Chinese adults. Among the five periods of time, the equation of Knudsen N was the best to estimate the 24-hour UIE except the morning period. Conclusion: Urinary iodine status at the individual level could be estimated by different creatinine-based equations at different periods of the day.

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Abstract P362: Validation of a Simple Method to Estimate Populational 24-h Urinary Sodium Excretion Based on a Casual Urine Specimen in an Adult Danish Population

Circulation ◽

10.1161/circ.125.suppl_10.ap362 ◽

2012 ◽

Vol 125 (suppl_10) ◽

Author(s):

Ulla Toft ◽

Charlotte Cerquira ◽

Torben Jørgensen

Keyword(s):

Sodium Excretion ◽

Sodium Intake ◽

Prediction Method ◽

Urinary Sodium Excretion ◽

Urinary Sodium ◽

Urine Specimen ◽

Urine Collection ◽

Danish Population ◽

Simple Method ◽

Spot Urine

Background: Tanaka et al (J Hum Hypert 2002; 16: 97-103) developed a simple method to estimate populational 24-h urinary sodium excretion using a casual urine specimen. However, this method was developed and validated in a Japanese population and thus this method might not be valid in populations that differ markedly from this population. Hypothesis: We assessed the hypothesis that the 24 hour urinary sodium excretion can be estimated from a casual spot urine using the Tanaka prediction method in a Danish general population. Methods: Overall 473 Danish individuals provided both a 24h urine collection and a spot urine sample. Data were collected in the Danthyr study (248 women aged 25-30 years and 60-65 years) and the Inter99 study (102 men and 113 women aged 30-60 years), respectively. Only participants with complete 24h urine collection (validated by the PABA method) were included. We compared the estimated daily sodium excretion through 24h urine (the gold standard) with the predicted 24 h sodium excretion from a causal urine specimen, using the Tanaka prediction method. Results: The predicted median 24 h sodium excretion (median [5 and 95 percentile]) was 8.6 gram [3.7;17.5] compared with a median measured 24 h sodium excretion of 8.9 [5.4; 13:1]. The mean (sd) residual (measured minus predicted 24 h sodium excretion) was 0.08 (3.7). The correlation (Spearman) between predicted and measured 24 h sodium excretion was 0.39 and the R 2 was 0.17. The proportion of individuals classified in the same or adjacent quintiles was 67%. Gross misclassification was found for 3% of the individuals. However, a Bland-Altman plot indicated a tendency of underestimation the sodium excretion for individuals with a high level of sodium excretion (>14 g per day). Conclusion: The Tanaka prediction model gives a reasonable estimate of sodium intake in a Danish population using casual spot urines. However, the validation study showed a tendency of underestimation of the sodium intake for individuals with a high sodium excretion (>14 g per day).

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Prediction of 24-Hour Urinary Sodium Excretion Using a Single Spot Urine Samples in Moroccan Population

E3S Web of Conferences ◽

10.1051/e3sconf/202131901066 ◽

2021 ◽

Vol 319 ◽

pp. 01066

Author(s):

Mohamed Idrissi ◽

Naima Saeid ◽

Anass Rami ◽

Mohammed El Mzibri ◽

Arthur Assako ◽

...

Keyword(s):

Sodium Excretion ◽

Sodium Intake ◽

Urinary Sodium Excretion ◽

Urinary Sodium ◽

Urine Collection ◽

Validation Data ◽

Data Set ◽

Single Spot ◽

Spot Urine ◽

Moroccan Population

Background: Excessive sodium intake is linked to high blood pressure. Estimating sodium intake is difficult. The 24-h urine collection is currently the recommended method for estimating intake but cumbersome for large population studies. Predictive model to estimate sodium intake based on single spot urine were developed, but showed inconsistency when used in extern populations. This study aims to develop a specific model for estimating sodium excretion over 24 hours for the Moroccan population. Methods: 371 participants in the urinary validation sub-study of the STEP-wise survey-Morocco 2017-2018 provided a valid 24-hour urine collection and spot urine specimens. Participant were randomly assigned to the training (n=183) and the validation data set (n=188). Results: A prediction model for 24-hour sodium excretion was developed. Adjusted R2 was 0.258. In the validation data set, correlation was 0.431 [95%CI; 0.258-0.580], and the adjusted R2 was 0.190. The Bland-Altman plot showed a nonsignificant small mean bias of -18 mg (95%CI, -213 to 177) in predicting 24-h urinary sodium excretion at the group level. At the individual level, limits of agreement were wide. Conclusion: This new model developed from a single spot urine could be used to predict the average 24-h sodium excretion of Moroccan adults.

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Effects of a Novel Contextual Just-In-Time Mobile App Intervention (LowSalt4Life) on Sodium Intake in Adults With Hypertension: Pilot Randomized Controlled Trial

JMIR mhealth and uhealth ◽

10.2196/16696 ◽

2020 ◽

Vol 8 (8) ◽

pp. e16696

Author(s):

Michael P Dorsch ◽

Maria L Cornellier ◽

Armella D Poggi ◽

Feriha Bilgen ◽

Peiyu Chen ◽

...

Keyword(s):

Blood Pressure ◽

Sodium Excretion ◽

Sodium Intake ◽

Urinary Sodium Excretion ◽

Mobile App ◽

Urinary Sodium ◽

Just In Time ◽

Spot Urine ◽

Low Sodium Diet ◽

Low Sodium

Background High dietary sodium intake is a significant public health problem in the United States. High sodium consumption is associated with high blood pressure and high risk of cardiovascular disease. Objective The aim of this study was to evaluate the effect of a just-in-time adaptive mobile app intervention, namely, LowSalt4Life, on reducing sodium intake in adults with hypertension. Methods In this study, 50 participants aged ≥18 years who were under treatment for hypertension were randomized (1:1, stratified by gender) into 2 groups, namely, the App group (LowSalt4Life intervention) and the No App group (usual dietary advice) in a single-center, prospective, open-label randomized controlled trial for 8 weeks. The primary endpoint was the change in the 24-hour urinary sodium excretion estimated from spot urine by using the Kawasaki equation, which was analyzed using unpaired two-sided t tests. Secondary outcomes included the change in the sodium intake measured by the food frequency questionnaire (FFQ), the 24-hour urinary sodium excretion, blood pressure levels, and the self-reported confidence in following a low-sodium diet. Results From baseline to week 8, there was a significant reduction in the Kawasaki-estimated 24-hour urinary sodium excretion calculated from spot urine in the App group compared to that in the No App group (–462 [SD 1220] mg vs 381 [SD 1460] mg, respectively; P=.03). The change in the 24-hour urinary sodium excretion was –637 (SD 1524) mg in the App group and –322 (SD 1485) mg in the No App group (P=.47). The changes in the estimated sodium intake as measured by 24-hour dietary recall and by FFQ in the App group were –1537 (SD 2693) mg and –1553 (SD 1764) mg while those in the No App group were –233 (SD 2150) mg and –515 (SD 1081) mg, respectively (P=.07 and P=.01, respectively). The systolic blood pressure change from baseline to week 8 in the App group was –7.5 mmHg while that in the No App group was –0.7 mmHg (P=.12), but the self-confidence in following a low-sodium diet was not significantly different between the 2 groups. Conclusions This study shows that a contextual just-in-time mobile app intervention resulted in a greater reduction in the dietary sodium intake in adults with hypertension than that in the control group over a 8-week period, as measured by the estimated 24-hour urinary sodium excretion from spot urine and FFQ. The intervention group did not show a significant difference from the control group in the self-confidence in following a low sodium diet and in the 24-hour urinary sodium excretion or dietary intake of sodium as measured by the 24-hour dietary recall. A larger clinical trial is warranted to further elucidate the effects of the LowSalt4Life intervention on sodium intake and blood pressure levels in adults with hypertension. Trial Registration ClinicalTrials.gov NCT03099343; https://clinicaltrials.gov/ct2/show/NCT03099343 International Registered Report Identifier (IRRID) RR2-10.2196/11282

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Effects of a Novel Contextual Just-In-Time Mobile App Intervention (LowSalt4Life) on Sodium Intake in Adults With Hypertension: Pilot Randomized Controlled Trial (Preprint)

10.2196/preprints.16696 ◽

2019 ◽

Author(s):

Michael P Dorsch ◽

Maria L Cornellier ◽

Armella D Poggi ◽

Feriha Bilgen ◽

Peiyu Chen ◽

...

Keyword(s):

Blood Pressure ◽

Sodium Excretion ◽

Sodium Intake ◽

Urinary Sodium Excretion ◽

Mobile App ◽

Urinary Sodium ◽

Just In Time ◽

Spot Urine ◽

Low Sodium Diet ◽

Low Sodium

BACKGROUND High dietary sodium intake is a significant public health problem in the United States. High sodium consumption is associated with high blood pressure and high risk of cardiovascular disease. OBJECTIVE The aim of this study was to evaluate the effect of a just-in-time adaptive mobile app intervention, namely, LowSalt4Life, on reducing sodium intake in adults with hypertension. METHODS In this study, 50 participants aged ≥18 years who were under treatment for hypertension were randomized (1:1, stratified by gender) into 2 groups, namely, the App group (LowSalt4Life intervention) and the No App group (usual dietary advice) in a single-center, prospective, open-label randomized controlled trial for 8 weeks. The primary endpoint was the change in the 24-hour urinary sodium excretion estimated from spot urine by using the Kawasaki equation, which was analyzed using unpaired two-sided t tests. Secondary outcomes included the change in the sodium intake measured by the food frequency questionnaire (FFQ), the 24-hour urinary sodium excretion, blood pressure levels, and the self-reported confidence in following a low-sodium diet. RESULTS From baseline to week 8, there was a significant reduction in the Kawasaki-estimated 24-hour urinary sodium excretion calculated from spot urine in the App group compared to that in the No App group (–462 [SD 1220] mg vs 381 [SD 1460] mg, respectively; P=.03). The change in the 24-hour urinary sodium excretion was –637 (SD 1524) mg in the App group and –322 (SD 1485) mg in the No App group (P=.47). The changes in the estimated sodium intake as measured by 24-hour dietary recall and by FFQ in the App group were –1537 (SD 2693) mg and –1553 (SD 1764) mg while those in the No App group were –233 (SD 2150) mg and –515 (SD 1081) mg, respectively (P=.07 and P=.01, respectively). The systolic blood pressure change from baseline to week 8 in the App group was –7.5 mmHg while that in the No App group was –0.7 mmHg (P=.12), but the self-confidence in following a low-sodium diet was not significantly different between the 2 groups. CONCLUSIONS This study shows that a contextual just-in-time mobile app intervention resulted in a greater reduction in the dietary sodium intake in adults with hypertension than that in the control group over a 8-week period, as measured by the estimated 24-hour urinary sodium excretion from spot urine and FFQ. The intervention group did not show a significant difference from the control group in the self-confidence in following a low sodium diet and in the 24-hour urinary sodium excretion or dietary intake of sodium as measured by the 24-hour dietary recall. A larger clinical trial is warranted to further elucidate the effects of the LowSalt4Life intervention on sodium intake and blood pressure levels in adults with hypertension. CLINICALTRIAL ClinicalTrials.gov NCT03099343; https://clinicaltrials.gov/ct2/show/NCT03099343 INTERNATIONAL REGISTERED REPORT RR2-10.2196/11282

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