ABSTRACT
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.
Subject(s)
Population Surveillance , Randomized Controlled Trials as Topic , Renin/blood , Sodium Chloride, Dietary/administration & dosage , Sodium/urine , Blood Pressure/drug effects , Blood Pressure/physiology , Cross-Sectional Studies , Humans , Hypertension/blood , Hypertension/diagnosis , Hypertension/urine , Population Surveillance/methods , Randomized Controlled Trials as Topic/methodsABSTRACT
OBJECTIVES: Accurate estimation of sodium intake by a precise and reproducible method is crucial in sodium intake reduction policy. This study tested the feasibility of 24-h urine (24HU) collection method and estimated sodium intake of a major city population from a representative adult sample. SUBJECTS/METHODS: A representative population (aged 20-65 years) was selected by list-assisted random-digit dialing method from a city with a population of one million. Sodium and potassium intakes (24HUNa and 24HUK, respectively) were measured with 24HU collection. RESULTS: Of those 496 individuals recruited, 24HU samples from 368 participants were determined to be properly collected and analyzed. The weighted mean of 24HUNa was 166.4 ± 68.1 mmol per day, much lower than 208.2 mmol of 24HUNa measured in Pusan (Korea; 1988 INTERSALT). The 24HUNa was highest in population aged 40-49 years, with a decrease after 50 years. Men had higher 24HUNa than women (182.0 ± 77.6 vs 151.4 ± 55.0 mmol per day). The sodium intake is higher than that found in survey conducted in the United Kingdom/Scotland and Finland, similar to that of Spain and lower than that of Portugal, Slovenia and Turkey. In contrast to 24HUNa, 24HUK increased continuously as age increased. CONCLUSIONS: This study enables us to compare sodium intake with the results of other surveys even from other countries, and reinforce the recommended introduction of the 24HU collection method in Korea. Sodium intake of the studied population was higher than the World Health Organization recommendation, suggesting the needs for further efforts to reduce sodium intake.
