Namyi Gu

Estimation of 24-Hour Urinary Sodium Excretion Using Spot Urine Samples

The present study evaluated the reliability of equations using spot urine (SU) samples in the estimation of 24-hour urine sodium excretion (24-HUNa). Equations estimating 24-HUNa from SU samples were derived from first-morning SU of 101 participants (52.4 ± 11.1 years, range 24–70 years). Equations developed by us and other investigators were validated with SU samples from a separate group of participants (n = 224, 51.0 ± 10.9 years, range 24–70 years). Linear, quadratic, and cubic equations were derived from first-morning SU samples because these samples had a sodium/creatinine ratio having the highest correlation coefficient for 24-HUNa/creatinine ratio (r = 0.728, p < 0.001). In the validation group, the estimated 24-HUNa showed significant correlations with measured 24-HUNa values. The estimated 24-HUNa by the linear, quadratic, and cubic equations developed from our study were not significantly different from measured 24-HUNa, while estimated 24-HUNa by previously developed equations were significantly different from measured 24-HUNa values. The limits of agreement between measured and estimated 24-HUNa by six equations exceeded 100 mmol/24-hour in the Bland-Altman analysis. All equations showed a tendency of under- or over-estimation of 24-HUNa, depending on the level of measured 24-HUNa. Estimation of 24-HUNa from single SU by equations as tested in the present study was found to be inadequate for the estimation of an individual’s 24-HUNa.

Effect of sodium intake on renin level: Analysis of general population and meta-analysis of randomized controlled trials

BACKGROUND We evaluated the association between sodium intake and plasma renin levels in the cross sectional study and meta-analysis of randomized controlled trials, whether there is a persistent elevation of plasma renin by longer-term sodium intake restriction. METHODS Plasma renin activity (PRA) and 24-h urine sodium (24HUNa) excretion were measured from individuals randomly selected from a community. Simple and multiple linear regression analyses adjusted for age, 24-h systolic blood pressure, 24-h average heart rate, fasting blood glucose and gender were performed. For meta-analysis, 74 studies published from 1975 to mid-2014 were identified in a systematic literature search using EMBASE, CINAHL, and MEDLINE. Random effects meta-analyses and a meta-regression analysis were performed. RESULTS Among the 496 participants recruited, 210 normotensive and 87 untreated hypertensive subjects were included in the analysis. There was no significant association between PRA and 24HUNa in the total population, or hypertensive and normotensive individuals. In the meta-analysis, the standard mean difference (SMD) of renin level by sodium intake reduction was 1.26 (95% CI: 1.08 to 1.44, Z=12.80, P<0.001, I(2)=87%). In the meta-regression analysis, an increase in a day of intervention was associated with a fall in SMD by -0.04 (95% CI: -0.05 to -0.02, Z=-5.27, P<0.001, I(2)=86%), indicating that longer duration of reduced sodium intake would lead to lesser SMD of renin level. CONCLUSIONS The present population based cross-sectional study and meta-analysis suggests that prolonged reduction in sodium intake is very unlikely associated with elevation of plasma renin levels.

Elevation of heart-femoral pulse wave velocity by short-term low sodium diet followed by high sodium diet in hypertensive patients with sodium sensitivity.

BACKGROUND/OBJECTIVES We compared changes in heart-femoral pulse wave velocity (hfPWV) in response to low sodium and high sodium diet between individuals with sodium sensitivity (SS) and resistance (SR) to evaluate the influence of sodium intake on arterial stiffness. SUBJECTS/METHODS Thirty-one hypertensive and 70 normotensive individuals were given 7 days of low sodium dietary approach to stop hypertension (DASH) diet (LSD, 100 mmol NaCl/day) followed by 7 days of high sodium DASH diet (HSD, 300 mmol NaCl/day) during 2 weeks of hospitalization. The hfPWV was measured and compared after the LSD and HSD. RESULTS The hfPWV was significantly elevated from LSD to HSD in individuals with SS (P = 0.001) independently of changes in mean arterial pressure (P = 0.037). Conversely, there was no significant elevation of hfPWV from LSD to HSD in individuals with SR. The percent change in hfPWV from the LSD to the HSD in individuals with SS was higher than that in individuals with SR. Subgroup analysis revealed that individuals with both SS and hypertension showed significant elevation of hfPWV from LSD to HSD upon adjusted analysis using changes of the means arterial pressure (P = 0.040). However, there was no significant elevation of hfPWV in individuals with SS and normotension. CONCLUSION High sodium intake elevated hfPWV in hypertensive individuals with SS, suggesting that high sodium intake increases aortic stiffness, and may contribute to enhanced cardiovascular risk in hypertensive individuals with SS.

Prevalence of Masked Hypertension: a Population-Based Survey in a Large City by Using 24-Hour Ambulatory Blood Pressure Monitoring

Background and Objectives We estimated the prevalence of hypertension and hypertension subtypes in a large semi-urban city in Korea, using 24-hour ambulatory blood pressure monitoring (ABPM) in a randomly selected sample population. Subjects and Methods A random sample (aged 20-65 years) from a city with an adult population of approximately 600000 was selected by using a list-assisted random digit dialing method. The 24-hour ABPM and conventional blood pressure measurement (CBPM) of these individuals were obtained. Results Among the 496 participants, valid 24-hour ABPM and CBPM were obtained from 462 (93%) individuals. The estimated prevalence of hypertension in Goyang was 17.54% by CBPM and 32.70% by 24-hour ABPM (p<0.01). In the age stratified analysis, both CBPM and 24-hour ABPM showed increased prevalence of hypertension with age. The estimated prevalence of masked hypertension was 16.22% and that of white-coat hypertension was 1.08%. Men had a higher prevalence of masked hypertension than women (20.79% vs. 11.86%, p=0.0295). The estimated prevalence of masked hypertension was 17.5%, 20.58%, 24.34%, and 13.29% in the age categories of 30s, 40s, 50s, and 60s, respectively. The estimated prevalence of masked uncontrolled hypertension was 26.79% in patients with hypertension who were taking antihypertensive medications. Conclusion The estimated prevalence of hypertension by 24-hour ABPM was higher than that by CBPM, revealing high prevalence of masked hypertension. The high prevalence of masked hypertension supports the adoption of ABPM in the national population survey and clinical practice to improve public health and reduce health care costs.

Relationship between 24-h urine sodium/potassium ratio and central aortic systolic blood pressure in hypertensive patients

Studies evaluating the relationship between measured 24-h urine sodium (24HUNa), potassium (24HUK) and aortic blood pressure (BP) are rare, and no such study has been performed with an Asian population. We evaluated the relationship between 24HUNa, 24HUK, casual BP, 24-h ambulatory BP and aortic BP by analyzing data from 524 participants with valid 24-h urine collection, 24-h ambulatory BP and central BP measurements (mean age 48.1±9.8 years, 193 men). Hypertension was defined as a 24-h ambulatory BP ⩾130/80 mm Hg or current treatment for hypertension (n=219). The participants with hypertension and high 24HUNa (mean 210.5±52.0 mmol  per day, range 151.0–432.0) showed higher 24-h systolic (P=0.037) and diastolic BP (P=0.037) and aortic systolic BP (AoSBP, P=0.038) than the participants with hypertension and low 24HUNa (mean 115.7±25.0 mmol per day, range 45.6–150.0), adjusted for confounders. The participants with hypertension and a high ratio of 24HUNa and 24HUK (24HUNa/24HUK, mean 4.03±1.00, range 2.93–7.96) had higher AoSBP than the participants with hypertension and a low 24HUNa/24HUK ratio (mean 2.13±0.54, range 0.53–2.91), adjusted for confounders (P=0.026). The participants with hypertension demonstrated a significant linear relationship between AoSBP and 24HUNa/24HUK ratio that was independent of 24HUNa, according to the multiple regression analysis (P=0.047). In hypertensive patients, 24HUNa/24HUK was positively and more strongly related to AoSBP compared with 24HUNa alone. The result indicates that high sodium and low potassium intake may increase the subsequent risk of cardiovascular disease by elevating AoSBP.

Visual Fatigue Induced by Viewing a Tablet Computer with a High-resolution Display

Purpose In the present study, the visual discomfort induced by smart mobile devices was assessed in normal and healthy adults. Methods Fifty-nine volunteers (age, 38.16 ± 10.23 years; male : female = 19 : 40) were exposed to tablet computer screen stimuli (iPad Air, Apple Inc.) for 1 hour. Participants watched a movie or played a computer game on the tablet computer. Visual fatigue and discomfort were assessed using an asthenopia questionnaire, tear film break-up time, and total ocular wavefront aberration before and after viewing smart mobile devices. Results Based on the questionnaire, viewing smart mobile devices for 1 hour significantly increased mean total asthenopia score from 19.59 ± 8.58 to 22.68 ± 9.39 (p < 0.001). Specifically, the scores for five items (tired eyes, sore/aching eyes, irritated eyes, watery eyes, and hot/burning eye) were significantly increased by viewing smart mobile devices. Tear film break-up time significantly decreased from 5.09 ± 1.52 seconds to 4.63 ± 1.34 seconds (p = 0.003). However, total ocular wavefront aberration was unchanged. Conclusions Visual fatigue and discomfort were significantly induced by viewing smart mobile devices, even though the devices were equipped with state-of-the-art display technology.

Estimating 24-Hour Urine Sodium From Multiple Spot Urine Samples.

The authors developed an equation to estimate 24‐hour urine sodium (24HUNa) using the average of three spot urine (SU) samples (morning‐first, morning, and evening) from 74 individuals and validated this equation using the average of three SU samples (morning‐first, daytime, and evening) from 174 additional individuals. Compared with previously published equations using a single SU sample, the currently developed equation using the average of three SU samples showed much lower bias from measured 24HUNa (−2.9 vs >10 mmol/24 h). The intraclass and concordance correlation coefficients of the proposed equation using the average of three SU samples were 0.909 and 0.832, respectively. The limits of agreement were −64.1–58.3 mmol/24 h and approximately 100 mmol/24 h for the currently developed and previously published equations, respectively. All equations showed a tendency to overestimate or underestimate 24HUNa in a manner dependent on the level of 24HUNa but irrespective of the number of SU samples considered. Nonetheless, among the currently tested equations, our equation using the average of three SU samples provided the best estimation of 24HUNa at a population level.

Survey on the undergraduate curriculum in clinical pharmacology and interns' prescribing ability in South Korea

Appropriate prescription writing is one of the critical medical processes affecting the quality of public health care. However, this is a complex task for newly qualified intern doctors because of its complex characteristics requiring sufficient knowledge of medications and principles of clinical pharmacology, skills of diagnosis and communication, and critical judgment. This study aims to gather data on the current status of undergraduate prescribing education in South Korea. Two surveys were administered in this study: survey A to 26 medical schools in South Korea to gather information on the status of undergraduate education in clinical pharmacology; and survey B to 244 intern doctors in large hospitals to gather their opinions regarding prescribing education and ability. In survey A, half of the responding institutions provided prescribing education via various formats of classes over two curriculums including lecture, applied practice, group discussions, computer-utilized training, and workshops. In survey B, we found that intern doctors have the least confidence when prescribing drugs for special patient populations, especially pregnant women. These intern doctors believed that a case-based practical training or group discussion class would be an effective approach to supplement their prescribing education concurrently or after the clerkship in medical schools or right before starting intern training with a core drug list. The results of the present study may help instructors in charge of prescribing education when communicating and cooperating with each other to improve undergraduate prescribing education and the quality of national medical care.

ISOLATED NOCTURNAL HYPERTENSION HAD HIGHER 24-HOUR URINE SODIUM/POTASSIUM RATIO THAN NORMOTENSION

Objective: Only few studies showed the association of salt intake with nocturnal blood pressure (BP). However, little is known about salt intake in patients with isolated nocturnal hypertension. Design and method: Among the 1128 participants, 740 participants who had complete 24-hour urine collection and valid 24-h ambulatory BP monitoring were analyzed. Participants were grouped in 4 groups: normotension (NT, n = 371), isolated daytime hypertension (IDHT, n = 26), isolated nocturnal hypertension (INHT, n = 177), and both-hypertension having both daytime and nocturnal hypertension (both-HT, n = 166). Results: The 24-hour urine sodium (24HUNa) was 155.4 ± 62.9, 164.1 ± 65.5, 169.8 ± 65.8 and 180.0 ± 72.2 mmol/24 hour, respectively. The 24-hour urine potassium (24HUK) was 56.6 ± 19.7, 51.3 ± 14.7, 60.1 ± 25.4 and 60.1 ± 21.4 mmol/24-hour and the 24-hour urine sodium/potassium ratio (24HUNa/24HUK) were 2.9 ± 1.2, 3.3 ± 1.0, 3.3 ± 3.2 and 3.2 ± 1.3, respectively. Compared to NT group, INHT had higher 24HUNa (p = 0.014), and both-HT had higher 24HUNa and 24HUNa/24HUK (p < 0.001 and 0.016, respectively). There was no difference in 24HUNa, 24HUNK and 24HUNa/24HUK between INHT and both-HT. In multivariate analysis controlled with age, gender, body mass index, estimated glomerular filtration rate, and use of diuretics, INHT showed significantly higher 24HUNa/24HUK than NT (p = 0.038). The difference of 24HUNa and 24HUNa/24HUK between NT and both-HT was not persistent in multivariate analysis. Conclusions: The result of present study suggests that high ratio of sodium/potassium intake may be a risk of isolated nocturnal hypertension.

[PP.15.01] ESTIMATION OF 24-H URINE SODIUM FROM SPOT URINE: A TENDENCY OF MOVING ESTIMATED MEAN TOWARD TO MEAN OF POPULATION FROM WHICH REGRESSION MODEL WAS ESTABLISHED

Objective: Most equations estimating 24-h urine sodium (e24HUNa) from single spot urine have developed by using regression model of sample population. Those equations have been challenged its tendency of under- and over estimation of e24HUNa depending on the amount of sodium intake. We hypothesized that the mean of e24HUNa from single spot urine depends on the mean of measured 24-h urine sodium (m24HUNa) of population from which regression model was established. Design and method: A population (n = 791) was divided into (1) septiles and (2) quintiles with the level of m24HUNa. In each septile, e24HUNa was calculated by using previously suggested equations (Kawasaki, Tanaka, and Danish equations), and compared to m24HUNa. In each quintile, e24HUNa was calculated by estimating equations developed from remainders of population by using regression model, and compared to m24HUNa. Results: Mean e24HUNa calculated by tested equations was higher than m24HUNa in septiles with lower m24HUNa compared to mean m24HUNa of development population from which regression equation was developed, but lower in septiles with higher m24HUNa, showing a tendency of moving e24HUNa toward to the mean of development population, from which regression equations were developed. Regression equations, developed from population excluding each quartile, showed overestimation in quartiles of low m24HUNa and overestimation in quartiles of high m24HUNa. Conclusions: Estimation of mean sodium intake at population level from single spot urine by using regression equations showed a tendency of moving the calculated mean toward to the mean of population, from which regression model was established. This phenomenon suggests that estimation of sodium intake at the population by using single spot urine should be reappraised.