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Pathogenetic studies have demonstrated that the interdependency of sodium and potassium affects blood pressure. Emerging evidences on the sodium-to-potassium ratio show benefits for a reduction in sodium and an increase in potassium compared to sodium and potassium separately. As presently there is no known review, this article examined the practical use of the sodium-to-potassium ratio in daily practice. Epidemiological studies suggest that the urinary sodium-to-potassium ratio may be a superior metric as compared to separate sodium and potassium values for determining the relation to blood pressure and cardiovascular disease risks. Higher correlations and better agreements are seen for the casual urine sodium-to-potassium ratio than for casual urine sodium or potassium alone when compared with the 24-h urine values. Repeated measurements of the casual urine provide reliable estimates of the 7-day 24-h urine value with less bias for the sodium-to-potassium ratio as compared to the common formulas used for estimating the single 24-h urine from the casual urine for sodium and potassium separately. Self-monitoring devices for the urinary sodium-to-potassium ratio measurement makes it possible to provide prompt onsite feedback. Although these devices have been evaluated with a view to support an individual approach for sodium reduction and potassium increase, there has yet to be an accepted recommended guideline for the sodium-to-potassium ratio. This review concludes with a look at the practical use of the sodium-to-potassium ratio for assistance in practical sodium reduction and potassium increase.

The Na/K ratio may be more strongly related to blood pressure and cardiovascular disease than sodium or potassium. The casual urine Na/K ratio can provide prompt on-site feedback, and with repeated measurements, may provide useful individual estimates of the 24-h ratio. The World Health Organization has published guidelines for sodium and potassium intake, but no generally accepted guideline prevails for the Na/K ratio. We used standardized data on 24 h and casual urinary electrolyte excretion obtained from the INTERSALT Study for 10,065 individuals aged 20-59 years from 32 countries (52 populations). Associations between the casual urinary Na/K ratio and the 24-h sodium and potassium excretion of individuals were assessed by correlation and stratification analyses. The mean 24-h sodium and potassium excretions were 156.0 mmol/24 h and 55.2 mmol/24 h, respectively; the mean 24-h urinary Na/K molar ratio was 3.24. Pearson's correlation coefficients (r) for the casual urinary Na/K ratio with 24-h sodium and potassium excretions were 0.42 and -0.34, respectively, and these were 0.57 and -0.48 for the 24-h ratio. The urinary Na/K ratio predicted a 24-h urine Na excretion of <85 mmol/day (the WHO recommended guidelines) with a sensitivity of 99.7% and 94.0%, specificity of 39.5% and 48.0%, and positive predictive value of 96.3% and 61.1% at the cutoff point of 1 in 24 h and casual urine Na/K ratios, respectively. A urinary Na/K molar ratio <1 may be a useful indicator for adherence to the WHO recommended levels of sodium and, to a lesser extent, the potassium intake across different populations; however, cutoff points for Na/K ratio may be tuned for localization.

Among individuals with hypertension, the prevalence of secondary hypertension has been reported to be ≈10%. More than half of individuals with secondary hypertension have associated hyperaldosteronism. However, given the current clinical environment, these patients often remain undiagnosed. We hypothesized that the urinary sodium/potassium ratio (Na/K) could be used as a simple, low-cost method of screening for hyperaldosteronism among individuals with hypertension in primary care and health examination settings. We recruited hypertensive individuals aged 30–69 years old who were not taking any antihypertensive medications from among participants in health examinations. Urinary Na and K were measured using second morning urine samples, and the plasma aldosterone concentration (PAC) was also measured. We evaluated the association of the second morning urine Na/K ratio (SMU Na/K) with a high PAC, defined as ≥90th percentile (24.3 ng/dL), using receiver operating characteristic (ROC) curves. Overall, 160 participants (108 men and 52 women) with a mean age of 54.3 years were eligible for this study. The area under the ROC curve for the relationship between SMU Na/K and high PAC was 0.77 (95% confidence interval [CI]: 0.59–0.95) in men and 0.64 (95% CI: 0.36–0.93) in women. In men, SMU Na/K values <1.0 could detect hyperaldosteronism with a sensitivity of 45.5%, a specificity of 97.9%, a positive predictive value of 71.4%, and a negative predictive value of 94.1%. The use of the urinary Na/K ratio may be appropriate as a method of screening for hyperaldosteronism in hypertensive men.

Background: Reducing the urinary sodium-to-potassium ratio is important for reducing both blood pressure and risk of cardiovascular disease. Among free-living Japanese individuals, we carried out a randomized trial to clarify the effect of lifestyle modification for lowering urinary sodium-to-potassium ratio using a self-monitoring device. Methods: This was an open, prospective, parallel randomized, controlled trial. Ninety-two individuals were recruited from Japanese volunteers. Participants were randomly allocated into intervention and control groups. A month-long dietary intervention on self-monitoring urinary sodium-to-potassium ratio was carried out using monitors (HEU-001F, OMRON Healthcare Co., Ltd., Kyoto, Japan). All participants had brief dietary education and received a leaflet as usual care. Monitors were handed out to the intervention group, but not to the control group. The intervention group was asked to measure at least one spot urine sodium-to-potassium ratio daily, and advised to lower their sodium-to-potassium ratio toward the target of less than 1. Outcomes included changes in 24-hour urinary sodium-to-potassium ratio, sodium excretion, potassium excretion, blood pressure, and body weight in both groups. Results: Mean measurement frequency of monitoring was 2.8 times/day during the intervention. Changes in urinary sodium-to-potassium ratio were −0.55 in the intervention group and −0.06 in the control group (P = 0.088); respective sodium excretion changes were −18.5 mmol/24 hours and −8.7 mmol/24 hours (P = 0.528); and corresponding potassium excretion was 2.6 mmol/24 hours and −1.5 mmol/24 hours (P = 0.300). No significant reductions were observed in either blood pressure or body weight after the intervention. Conclusions: Providing the device to self-monitor a sodium-to-potassium ratio did not achieve the targeted reduction of the ratio in “pure self-management” settings, indicating further needs to study an effective method to enhance the synergetic effect of dietary programs and self-monitoring practice to achieve the reduction. However, we cannot deny the possibility of reducing sodium-to-potassium ratio using a self-monitoring device.

High sodium-to-potassium ratios are associated with elevated blood pressure levels and an increased risk of cardiovascular diseases. We aimed to determine whether urinary sodium-to-potassium ratios fluctuate diurnally during the day to understand measured values of casual urinary sodium-to-potassium ratios. A total of 13,277 casual urine specimens were collected under free-living conditions from 122 Japanese normotensive and hypertensive individuals. Participants collected all casual urine samples in aliquot tubes, reported urine volumes and the time at each voiding for 10-22 days. Then, specimens were classified into hourly data. Diurnal patterns of urinary sodium-to-potassium ratios and urinary concentrations of sodium and potassium were evaluated. Overall mean values of hourly urinary sodium-to-potassium ratios were highest (4.1-5.0) in the early morning, lower (3.3-3.8) in the daytime and higher (4.0-4.4) toward evening hours. The mean urinary sodium and potassium concentrations were the lowest (90-110 and 24-32 mmol l , respectively) during the early morning and higher (110-140 and 35-43 mmol l , respectively) after mid-morning. Diurnal variability of potassium concentrations was larger than for sodium concentrations. Diurnal variations in urinary sodium-to-potassium ratios were comparable between normotensive and hypertensive individuals, between hypertensive individuals with and without antihypertensive medications, and among age and gender-specific subgroups. Overall mean hourly urinary sodium-to-potassium ratios fluctuated diurnally under free-living conditions and were higher during the morning and evening and lower during the daytime compared with 24-h urinary sodium-to-potassium ratios. Diurnal variation in urinary sodium-to-potassium ratios should be considered to understand actual daily dietary levels and avoid over- and under-estimation in clinical practice.

ObjectivesOur aim was to assess seasonal variation in home blood pressure (BP) among free-living nationwide participants using home BP values accumulated from a web-based healthcare platform established in Japan.SettingsAn observational study. OMRON Healthcare Co., Ltd. has been developing web-based personal healthcare record systems in Japan since November 2010; over two million voluntary participants had joined this platform in September 2015. Nationwide home BP measurements made by oscillometric-type electronic sphygmomanometers from over 110 000 voluntary participants have been transmitted to the system from devices.ParticipantsSeasonal variation in home BP was evaluated among 64 536 (51 335 men, 13 201 women; mean age 52.9 years) free-living nationwide users for whom data were automatically and simultaneously transmitted to the system from devices.Primary outcome measuresMean monthly and weekly home BP.ResultsIn multiple regression analysis, the relationship between BP and temperature was a significant inverse association, independent of age, gender and geological locations. Highest and lowest BP was observed in December and July, respectively. Substantial seasonal differences in the mean values of morning and evening home systolic BP between summer and winter were 6.2 mmHg and 5.5 mmHg in men, and 7.3 mmHg and 6.5 mmHg in women. Seasonal variation was a little greater in older (7.3 mmHg in men, 8.7 mmHg in women) than in younger individuals (5.8 mmHg in men, 6.5 mmHg in women). BP from February to July was approximately 1.5 mmHg lower than the value from August to December.ConclusionsA web-based healthcare platform has enabled easier monitoring of population-wide BP. Tighter BP control is necessary in winter than in summer, and especially in a colder climate toward winter than toward summer. New technologies using web-based self-monitoring systems for health-related indexes are expected to initiate a new phase of cardiovascular disease prevention and public health promotion.

Introduction: Although several approaches for approximating daily Na intake and the Na/K ratio using casual urine are available, the most useful method remains unclear during daily practice and at home. Methods: Twenty-seven participants measured their casual urinary Na/K ratio repeatedly using a Na/K ratio monitor and also measured overnight urine once daily using a monitoring device which delivers on-site feedback to estimate their salt intake under unrestricted, low-salt (LS) (6 g/day), and high-salt (HS) (12 g/day) diets. Results: The monitoring method utilizing overnight urine to estimate daily Na remained insensitive, resulting in significant overestimation during the LS diet and underestimation during the HS diet periods; estimated salt intake during the LS and HS diet periods plateaued at 7–8 g/day and 9–10 g/day within 3 day; mean estimated salt intake was 11.3 g/day, 7.9 g/day, and 9.8 g/day on the last day of the unrestricted, LS, and HS diets; the coefficient of variation (CV) of the estimated Na intake was 0.23 and 0.17 in the latter half of the low- and high-salt diet periods, respectively. The mean urinary Na/K molar ratio was 5.6, 2.5, and 5.3 on the last day of the unrestricted, LS, and HS diets; the CV of the daily mean Na/K ratio was 0.41 and 0.36 in the latter half of the LS and HS diet periods, respectively. The urinary Na/K ratio during the LS and HS diet periods plateaued within 2 days. The monitoring method based on the daily mean of the casual urinary Na/K ratio reflected the actual change in Na intake, and the estimated value tracked the actual changes in salt intake with smaller difference than the overnight urine estimates when using the estimation coefficient set at 2; estimated salt intake during the LS and HS diet periods plateaued at 5–6 g/day and 10–12 g/day within 2–3 day; mean estimated salt intake was 11.0 g/day, 5.7 g/day, and 10.7 g/day on the last day of the unrestricted, LS, and HS diets, respectively. Discussion/Conclusion: Estimates of daily Na intake derived from overnight urine may remain insensitive during dietary interventions. The urinary Na/K ratio reflects the actual change in Na intake during dietary modification and may serve as a practical marker, particularly during short-term interventions. Conversion from the urinary Na/K ratio to estimated salt intake may be useful, if the coefficient was set appropriate by further investigations.

This study aimed to investigate the incidence rates and predictors of lower limb fractures in a general Japanese population. NIPPON DATA is a nationwide, long-term, prospective cohort study of individuals who participated in the National Cardiovascular Survey Japan and the National Nutrition Survey in 1990. Overall, 3,134 individuals (1,827 women, 1,307 men) who participated in follow-up assessments in 1995, 2000, and/or 2006 were included in the present analysis. The outcomes of this study were lower limb fractures (including proximal femur fractures). The mean age at baseline was 63.8 years in women and 63.1 years in men. The average body mass index (BMI) was 23.3 kg/m2 in women and 22.9 kg/m2 in men. During a mean follow-up of 12.1 years, 271 total lower limb fractures were observed. In women, older age, lower BMI, and less intake of vegetables were associated with increased risks of proximal femur fractures. With regard to the outcome of total lower limb fractures, less intake of vegetables and regular exercise were significant predictors in women. Calcium intake was not significantly associated with proximal femur or total lower limb fractures. There were no significant predictors of proximal femur or total lower limb fractures in men, except for age. Aging was a significant risk factor for proximal femur and total lower limb fractures in both men and women. With regard to modifiable risk factors, low BMI and low intake of vegetables were associated with increased risks of proximal femur and/or total lower limb fractures in the general population of Japanese women.

The Na/K ratio is considered to be a useful index, the monitoring of which allows an effective Na reduction and K increase, because practical methods (self-monitoring devices and reliable individual estimates from spot urine) are available for assessing these levels in individuals. An intervention trial for lowering the Na/K ratio has demonstrated that a reduction of the Na/K ratio mainly involved Na reduction, with only a small change in K. The present study aimed to clarify the relationship between dietary Na intake and the urinary Na/K molar ratio, using standardized low- and high-salt diets, with an equal dietary K intake, to determine the corresponding Na/K ratio. Fourteen healthy young adult volunteers ingested low-salt (3 g salt per day) and high-salt (20 g salt per day) meals for seven days each. Using a portable urinary Na/K meter, participants measured their spot urine at each voiding, and 24-h urine was collected on the last day of each diet period. On the last day of the unrestricted, low-salt, and high-salt diet periods, the group averages of the 24-h urine Na/K ratio were 4.2, 1.0, and 6.9, while the group averages of the daily mean spot urine Na/K ratio were 4.2, 1.1, and 6.6, respectively. The urinary Na/K ratio tracked changes in dietary salt intake, and reached a plateau approximately three days after each change in diet. Frequent monitoring of the spot urine Na/K ratio may help individuals adhere to an appropriate dietary Na intake.