Urinary electrolyte excretion, alcohol consumption, and blood pressure in the Scottish heart health study

Sodium Intake and Health: What Should We Recommend Based on the Current Evidence?

Several health organizations recommend low sodium intake (below 2.3 g/day, 5.8 g/day of salt) for entire populations, on the premise that lowering of sodium intake, irrespective of its level of intake, will lower blood pressure and, in turn, will result in a lower incidence of cardiovascular disease. These guidelines were developed without effective interventions to achieve long term sodium intakes at low levels in free-living individuals and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with average levels of intake). In this review, we examine whether advice to consume low amounts of sodium is supported by robust evidence. We contend that current evidence indicates that most people around the world consume a moderate range of dietary sodium (3 to 5 g/day), that this level of intake is associated with the lowest risk of cardiovascular disease and mortality, and that the risk of adverse health outcomes increases when sodium intakes exceeds 5 g/day or is below 3 g/day. While the current evidence has limitations, it is reasonable, based upon prospective cohort studies, to suggest a mean target of below 5 g/day in populations, while awaiting the results of large randomized controlled trials of sodium reduction on cardiovascular disease and death.

Metabolites and Hypertension: Insights into Hypertension as a Metabolic Disorder: 2019 Harriet Dustan Award

For over 100 years, essential hypertension has been researched from different perspectives ranging from genetics, physiology, and immunology to more recent ones encompassing microbiology (microbiota) as a previously underappreciated field of study contributing to the cause of hypertension. Each field of study in isolation has uniquely contributed to a variety of underlying mechanisms of blood pressure regulation. Even so, clinical management of essential hypertension has remained somewhat static. We, therefore, asked if there are any converging lines of evidence from these individual fields that could be amenable for a better clinical prognosis. Accordingly, here we present converging evidence which support the view that metabolic dysfunction underlies essential hypertension.

Increased Aortic Characteristic Impedance Explains Relations Between Urinary Na + /K + and Pulse or Systolic Blood Pressure

Alterations in sodium (Na + ) relative to potassium (K + ) intake increase systolic blood pressure, effects in-part attributed to enhanced pulsatile loads (pulse pressure) beyond steady-state pressures (mean arterial pressure). Whether this effect is through reversible changes (increases in blood volume and hence aortic flow [Q] or wave reflection [Pb]), or potentially irreversible structural changes in the proximal aorta, is unknown. In 581 black South Africans, we determined 24-hour urinary Na + and K + excretion and aortic function from central aortic pressure (radial pulse wave analysis [SphygmoCor software]), velocity, and diameter measurements. Proximal aortic function was assessed from characteristic impedance (Zc). Beyond mean arterial pressure and additional confounders, urinary Na + /K + was independently associated with Zc ( P <0.005) but not peak aortic Q ( P =0.30) or alternative aspects of Q or ejection volume. Although age was strongly associated with proximal aortic diameter, no independent relations between urinary Na + /K + and aortic diameter were noted ( P =0.17). Relations between urinary Na + /K + and Zc translated into independent relations with early systolic compression wave pressures (QxZc [P QxZc ]) and aortic forward wave pressures but not Pb. Moreover, neither reflected wave magnitude ( P =0.92) nor aortic pulse wave velocity were independently associated with urinary Na + /K + . In product of coefficient mediation analysis, the independent relations between urinary Na + /K + and peak aortic or brachial pulse pressure or systolic blood pressure were accounted for by Zc and P QxZc . In conclusion, abnormalities in Na + /K + intake determine pulse pressure or systolic blood pressure beyond mean arterial pressure mainly through potentially irreversible impacts on proximal aortic impedance rather than readily modifiable increases in aortic flow (blood volume) or wave reflection.

Increased urinary sodium excretion is associated with systolic blood pressure in first degree relatives of hypertensive patients in Ibadan, Southwestern Nigeria

INTRODUCTION

Understanding the risk factors of hypertension has led to a better understanding of the pathogenesis, prevention and reduction in morbidity of hypertension. It is well known that offsprings of hypertensive parents have an increased risk of developing hypertension. It is therefore necessary to explore the physiological differences between normotensive patients with and without a positive family history of hypertension with respect to their urinary excretion of sodium.

METHODS

This study was carried out at the University College Hospital, Ibadan Nigeria, to determine if normotensive patients with a positive family history of hypertension are different with respect to their urinary excretion of electrolytes and blood pressure. It examined the relationship between 24-hour urinary excretion of sodium, chloride and potassium, urea and creatinine and blood pressure in subjects with and without family history of hypertension. It was a case-control study of sixty-two subjects: normotensive patients' first degree relatives of primary hypertensive patients and normotensive patients without positive family history.

RESULTS

The mean (SD) systolic blood pressures for subjects with and without family history of hypertension were significantly different: 120.0(22.25) and 105.0(17.50) respectively, (p=0.001). The mean arterial blood pressures were significantly different: 86.4(10.2) mmHg and 80.1(8.1) mmHg respectively (p=0.010). The mean (SD) 24-hour urinary excretion of sodium for normotensive patients with and without positive family history of hypertension were 180.5 (45.50) mEq/L, and 156.0(36.25) mEq/L respectively. Systolic blood pressure and 24-hour urinary excretion of sodium was also higher in normotensive subjects with a positive family history of hypertension.

CONCLUSION

Systolic blood pressure and twenty-four hour urinary excretion of sodium were higher in normotensive subjects with a positive family history of hypertension than in those without a family history of hypertension.

The Ongoing Sodium Controversy - Between PURE and NutriCode 1

The impact of sodium intake on cardiovascular health has long been a subject of controversial debates. On the one hand, the World Health Organization (WHO) and the American Heart Association (AHA) have argued for a target of 1500-2000 mg of sodium per day (4-5 g sodium chloride daily). On the other hand, this recommendation has been accompanied by a growing body of criticism. Recently, the results of the PURE and the NutriCode study have flared up the "salt controversy". Actually, the results of the PURE study seem to strengthen the position of those who have called into question the AHA and WHO guidelines for daily sodium intake whereas those who recommend a considerable salt reduction believe that the NutriCode study confirm their conviction. In this paper, the results of the PURE and NutriCode study will be discussed and evaluated with regard to practical consequences.

Advanced method used for hypertension's risk factors stratification: support vector machines and gravitational search algorithm

BACKGROUND

The aim of this study is to present an objective method based on support vector machines (SVMs) and gravitational search algorithm (GSA) which is initially utilized for recognition the pattern among risk factors and hypertension (HTN) to stratify and analysis HTN's risk factors in an Iranian urban population.

METHODS

This community-based and cross-sectional research has been designed based on the probabilistic sample of residents of Isfahan, Iran, aged 19 years or over from 2001 to 2007. One of the household members was randomly selected from different age groups. Selected individuals were invited to a predefined health center to be educated on how to collect 24-hour urine sample as well as learning about topographic parameters and blood pressure measurement. The data from both the estimated and measured blood pressure [for both systolic blood pressure (SBP) and diastolic blood pressure (DBP)] demonstrated that optimized SVMs have a highest estimation potential.

RESULTS

This result was particularly more evident when SVMs performance is evaluated with regression and generalized linear modeling (GLM) as common methods. Blood pressure risk factors impact analysis shows that age has the highest impact level on SBP while it falls second on the impact level ranking on DBP. The results also showed that body mass index (BMI) falls first on the impact level ranking on DBP while have a lower impact on SBP.

CONCLUSION

Our analysis suggests that salt intake could efficiently influence both DBP and SBP with greater impact level on SBP. Therefore, controlling salt intake may lead to not only control of HTN but also its prevention.

Reducing salt intake for prevention of cardiovascular disease--times are changing

The evidence relating blood pressure to salt intake in humans originates from population studies and randomized clinical trials of interventions on dietary salt intake. Estimates from meta-analyses of trials in normotensive subjects generally are similar to estimates derived from prospective population studies (+1.7 mm Hg increase in systolic blood pressure per 100-mmol increment in 24-hour urinary sodium). This estimate, however, does not translate into an increased risk of incident hypertension in subjects consuming a high salt diet. Prospective studies relating health outcomes to 24-hour urinary sodium excretion produced inconsistent results. Taken together, available evidence does not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level, although the blood pressure-lowering effect of dietary sodium restriction might be of value in hypertensive patients.

Association of urinary sodium and potassium excretion with blood pressure

BACKGROUND

Higher levels of sodium intake are reported to be associated with higher blood pressure. Whether this relationship varies according to levels of sodium or potassium intake and in different populations is unknown.

METHODS

We studied 102,216 adults from 18 countries. Estimates of 24-hour sodium and potassium excretion were made from a single fasting morning urine specimen and were used as surrogates for intake. We assessed the relationship between electrolyte excretion and blood pressure, as measured with an automated device.

RESULTS

Regression analyses showed increments of 2.11 mm Hg in systolic blood pressure and 0.78 mm Hg in diastolic blood pressure for each 1-g increment in estimated sodium excretion. The slope of this association was steeper with higher sodium intake (an increment of 2.58 mm Hg in systolic blood pressure per gram for sodium excretion >5 g per day, 1.74 mm Hg per gram for 3 to 5 g per day, and 0.74 mm Hg per gram for <3 g per day; P<0.001 for interaction). The slope of association was steeper for persons with hypertension (2.49 mm Hg per gram) than for those without hypertension (1.30 mm Hg per gram, P<0.001 for interaction) and was steeper with increased age (2.97 mm Hg per gram at >55 years of age, 2.43 mm Hg per gram at 45 to 55 years of age, and 1.96 mm Hg per gram at <45 years of age; P<0.001 for interaction). Potassium excretion was inversely associated with systolic blood pressure, with a steeper slope of association for persons with hypertension than for those without it (P<0.001) and a steeper slope with increased age (P<0.001).

CONCLUSIONS

In this study, the association of estimated intake of sodium and potassium, as determined from measurements of excretion of these cations, with blood pressure was nonlinear and was most pronounced in persons consuming high-sodium diets, persons with hypertension, and older persons. (Funded by the Heart and Stroke Foundation of Ontario and others.).

The population risks of dietary salt excess are exaggerated

Policy positions on salt consumption (based largely on the association of sodium and blood pressure [BP]) has remained unchanged since the 1970s, until recently. However, this is beginning to change as new evidence emerges. The evidence supports a strong association of sodium with BP and cardiovascular disease events in hypertensive individuals, the elderly, and those who consume > 6 g/d of sodium. However, there is no association of sodium with clinical events at 3 to 6 g/day and a paradoxical higher rate of events at < 3 g/day. Therefore, until new evidence emerges, the optimal range of sodium consumption should be considered to be between 3 and 6 g/d. Population-wide sodium reduction is not justified in countries such as Canada.

Salt and public health: contested science and the challenge of evidence-based decision making

For more than four decades, starting in the late 1960s, a sometimes furious battle has raged among scientists over the extent to which elevated salt consumption has adverse implications for population health and contributes to deaths from stroke and cardiovascular disease. Various studies and trials have produced conflicting results. Despite this scientific controversy over the quality of the evidence implicating dietary salt in disease, public health leaders at local, national, and international levels have pressed the case for salt reduction at the population level. This article explores the development of this controversy. It concludes that the concealment of scientific uncertainty in this case has been a mistake that has served neither the ends of science nor good policy. The article poses questions that arise from this debate and frames the challenges of formulating evidence-based public health practice and policy, particularly when the evidence is contested.

Insulin resistance and the relationship between urinary Na(+)/K(+) and ambulatory blood pressure in a community of African ancestry

BACKGROUND

Although groups of African descent are particularly sensitive to blood pressure (BP) effects of salt intake, the role of obesity and insulin resistance in mediating this effect is uncertain. We determined whether obesity or insulin resistance is independently associated with urinary Na(+)/K(+)-BP relationships in a community sample of African ancestry.

METHODS

We measured 24-hour urinary Na(+)/K(+), homeostasis model assessment of insulin resistance (HOMA-IR), and nurse-derived conventional and 24-hour ambulatory BP in 331 participants from a South African community sample of black African descent not receiving treatment for hypertension.

RESULTS

With adjustments for diabetes mellitus and the individual terms, an interaction between waist circumference and urinary Na(+)/K(+) was associated with day diastolic BP (P < 0.05) and an interaction between log HOMA-IR and urinary Na(+)/K(+) was associated with 24-hour and day systolic (P < 0.05) and 24-hour, day, and night diastolic (P < 0.002; P < 0.001) BP. The multivariable-adjusted relationship between urinary Na(+)/K(+) and night diastolic BP increased across tertiles of HOMA-IR (tertile 1: β-coefficient = -0.79 ± 0.47; tertile 2: β-coefficient = 0.65 ± 0.35; tertile 3: β-coefficient = 1.03 ± 0.46; P < 0.05 tertiles 3 and 2 vs. 1). The partial correlation coefficients for relationships between urinary Na(+)/K(+) and 24-hour (partial r = 0.19; P < 0.02), day (partial r = 0.17; P < 0.05), and night (partial r = 0.18; P < 0.02) diastolic BP in participants with log HOMA-IR greater than or equal to the median were greater than those for relationships between urinary Na(+)/K(+) and 24-hour (partial r = -0.08; P = 0.29), day (partial r = -0.10; P < 0.22), and night (partial r = -0.06; P = 0.40) diastolic BP in participants with log HOMA-IR less than the median (comparisons of r values: P < 0.05).

CONCLUSIONS

Insulin resistance may modify the relationship between salt intake, indexed by urinary Na(+)/K(+), and ambulatory BP in groups of African descent.

[Prevalence of hypertension in El-Menia oasis, Algeria, and metabolic characteristics in population]

INTRODUCTION

El-Menia is an oasis located in the middle of Algerian Sahara. The drinking water in this oasis has low sodium content. The objectives of this study were to estimate the prevalence of hypertension, to describe the metabolic characteristics of population study and to assess the factors associated with blood pressure levels.

METHODS

A cross sectional study was conducted in 2010. Subjects (n=722) were selected from individuals aged 40 years or older by random cluster sampling. Blood pressure measurements, combined with a clinical questionnaire, and standard blood samples for the detection of dyslipidemia and diabetes mellitus, were collected.

RESULTS

Sixty-seven percent of subjects were females and 18% were black. The mean age was 58.5 ± 13.2 years. The prevalence of hypertension was 50.2%: 49.7% in females and 51.3% in males. The factors associated with presence of hypertension following a logistic multivariate regression were age, skin colour, waist circumference, and plasma glucose. The treatment and control of hypertension were 41% and 20% respectively.

CONCLUSIONS

The prevalence oh hypertension was high in this oasis and the rate of treatment control was low. Our findings suggest that appropriate healthcare should be given to hypertensive subjects, including a better information on hypertension.

ADCYAP1R1 and asthma in Puerto Rican children

RATIONALE

Epigenetic and/or genetic variation in the gene encoding the receptor for adenylate-cyclase activating polypeptide 1 (ADCYAP1R1) has been linked to post-traumatic stress disorder in adults and anxiety in children. Psychosocial stress has been linked to asthma morbidity in Puerto Rican children.

OBJECTIVES

To examine whether epigenetic or genetic variation in ADCYAP1R1 is associated with childhood asthma in Puerto Ricans.

METHODS

We conducted a case-control study of 516 children ages 6-14 years living in San Juan, Puerto Rico. We assessed methylation at a CpG site in the promoter of ADCYAP1R1 (cg11218385) using a pyrosequencing assay in DNA from white blood cells. We tested whether cg11218385 methylation (range, 0.4-6.1%) is associated with asthma using logistic regression. We also examined whether exposure to violence (assessed by the Exposure to Violence [ETV] Scale in children 9 yr and older) is associated with cg11218385 methylation (using linear regression) or asthma (using logistic regression). Logistic regression was used to test for association between a single nucleotide polymorphism in ADCYAP1R1 (rs2267735) and asthma under an additive model. All multivariate models were adjusted for age, sex, household income, and principal components.

MEASUREMENTS AND MAIN RESULTS

EACH 1% increment in cg11218385 methylation was associated with increased odds of asthma (adjusted odds ratio, 1.3; 95% confidence interval, 1.0-1.6; P = 0.03). Among children 9 years and older, exposure to violence was associated with cg11218385 methylation. The C allele of single nucleotide polymorphism rs2267735 was significantly associated with increased odds of asthma (adjusted odds ratio, 1.3; 95% confidence interval, 1.02-1.67; P = 0.03).

CONCLUSIONS

Epigenetic and genetic variants in ADCYAP1R1 are associated with asthma in Puerto Rican children.

African ancestry and lung function in Puerto Rican children

BACKGROUND

Puerto Rican and African American subjects share a significant proportion of African ancestry. Recent findings suggest that African ancestry influences lung function in African American adults.

OBJECTIVE

We sought to examine whether a greater proportion of African ancestry is associated with lower FEV(1) and forced vital capacity (FVC) in Puerto Rican children independently of socioeconomic status, health care access, or key environmental/lifestyle factors.

METHODS

We performed a cross-sectional case-control study of 943 Puerto Rican children aged 6 to 14 years with (n= 520) and without (n= 423) asthma (defined as physician-diagnosed asthma and wheeze in the prior year) living in Hartford, Connecticut (n= 383), and San Juan, Puerto Rico (n= 560). We estimated the percentage of African racial ancestry in study participants using genome-wide genotypic data. We tested whether African ancestry is associated with FEV(1) and FVC using linear regression. Multivariate models were adjusted for indicators of socioeconomic status and health care and selected environmental/lifestyle exposures.

RESULTS

After adjustment for household income and other covariates, each 20% increment in African ancestry was significantly associated with lower prebronchodilator FEV(1) (-105 mL; 95% CI, -159 to -51 mL; P< .001) and FVC (-133 mL; 95% CI, -197 to -69 mL; P< .001) and postbronchodilator FEV(1) (-152 mL; 95% CI, -210 to -94 mL; P< .001) and FVC (-145 mL; 95% CI, -211 to -79 mL; P< .001) in children with asthma. Similar but weaker associations were found for prebronchodilator and postbronchodilator FEV(1) (change for each 20% increment in African ancestry, -78 mL; 95% CI, -131 to -25 mL; P= .004) and for postbronchodilator FVC among children without asthma.

CONCLUSIONS

Genetic factors, environmental/lifestyle factors, or both correlated with African ancestry might influence childhood lung function in Puerto Rican subjects.

Aldosterone-to-renin ratio and the relationship between urinary salt excretion and blood pressure in a community of African ancestry

BACKGROUND

Although aldosterone influences the effect of salt intake on blood pressure (BP), the extent to which this occurs at a population level is uncertain. We therefore aimed to determine, at a community level in a group of African descent, whether in the absence of primary aldosteronism, the relationship between salt intake and BP is modified by circulating aldosterone, and the extent to which this occurs.

METHODS

In 575 participants of African ancestry (age >16 years), we assessed whether aldosterone-to-renin ratio (ARR) is associated with the relationship between urinary sodium (Na(+))-to-potassium (K(+)) ratio (urinary Na(+)/K(+)) (from 24-h urine samples), an index of salt intake, and BP.

RESULTS

With adjustments for confounders, interactions between ARR and urinary Na(+)/K(+) were independently associated with systolic BP (SBP) (P < 0.0001), an effect that was accounted for by interactions between serum aldosterone concentrations and urinary Na(+)/K(+) (P < 0.0001), but not between plasma renin concentrations and urinary Na(+)/K(+) (P = 0.52). The interaction between ARR and urinary Na(+)/K(+) translated into a marked difference in the relationship between urinary Na(+)/K(+) and SBP in participants above compared to below the median for ARR (effect of 1 s.d. increase in urinary Na(+)/K(+) on SBP: ARR > median = 4.2 ± 0.6 mm Hg; ARR < median = 1.2 ± 0.4 mm Hg, P < 0.0001). In addition, participants with urinary Na(+)/K(+) above the median had higher multivariate-adjusted SBP (P < 0.001) only if ARR was also above the median.

CONCLUSIONS

In groups of African descent, in the absence of primary aldosteronism, an increased aldosterone concentration relative to renin modifies a substantial proportion of the relationship between urinary Na(+)/K(+) and BP at a community level.

Relationship Between Urinary Salt Excretion and Pulse Pressure and Central Aortic Hemodynamics Independent of Steady State Pressure in the General Population

Although central pulse pressure (PPc) is strongly related to central mean arterial pressure (MAPc), PPc predicts cardiovascular outcomes beyond MAPc. Whether modifiable risk factors for hypertension contribute to PPc and its determinants, independent of MAPc, is uncertain. In 635 randomly recruited participants, we assessed the independent relationship between 24-hour urinary sodium (Na + ) or potassium (K + ) excretion and brachial artery PP (in office or 24-hour; n=487), PPc, the forward (P1) and augmented (Paug) pressure wave components of PPc, central augmentation index, and determinants of central pressure waves, including aortic pulse wave velocity, effective reflecting distance, and reflective wave transit time. Central dynamics were determined using applanation tonometry of the carotid, femoral, and radial arteries. With adjustments for potential confounders, urinary Na + /K + was independently associated with in-office, central, and 24-hour PP, as well as Paug, P1, and central augmentation index ( P <0.05 to P <0.005). With further adjustments for MAPc (or diastolic BP), urinary Na + /K + was independently associated with PPc, 24-hour PP, Paug, P1, and central augmentation index ( P <0.05 to P =0.005) but not with in-office PP, pulse wave velocity, effective reflecting distance, or reflective wave transit time. In conclusion, in a population of African ancestry, urinary salt excretion is independently related to central and 24-hour PP independent of MAPc or diastolic BP, effects that are attributed to increases in both P1 and Paug but not to pulse wave velocity. Hence, modifying salt intake could influence cardiovascular risk through effects on 24-hour and central PPs, as well as P1 and Paug, independent of steady-state pressure (MAP or diastolic BP) or pulse wave velocity.

Salt and Blood Pressure

Current evidence does not support the view that the claimed association between salt intake and blood pressure is causal. In intercultural studies it is impossible to distinguish between a genuinely causal relationship and a relationship due to the role of salt intake as a marker for different life-styles. Physiological studies suggest that the Western intake of salt corresponds to a physiological set point selected when free choice is offered as the mid-point between harmful physiological extremes. When flawed intervention studies are excluded there is no evidence that a moderate reduction in salt intake would produce a significant blood pressure fall in healthy individuals although blood pressure falls can be produced in some hypertensive subjects.

Sodium and asthma: something borrowed, something new?

Some early studies have called attention to the potential contribution of sodium (both dietary and serum levels) in airway-related disease, although the picture was not entirely clear. Two recent developments may now allow a more careful consideration of this: first, the greatly improved understanding of the role of salt in hypertension (particularly the identification of subgroups of salt-sensitive individuals within the general population), and second, the recent discovery of the role of the Na(+)/Ca(2+) exchanger in smooth muscle function. Here, we first review those two developments and then apply them to airway smooth muscle and asthma.

The influence of dietary sodium on blood pressure

The goal of this essay is to examine the evidence relating salt intake to blood pressure in humans. Despite studies involving many thousands of subjects and patients performed in many hundreds of centers the issue remains controversial-indeed far more controversial than seems appropriate. There is little disagreement that in some animal models and in some patients with hypertension salt intake can exert a rather substantial influence. There is more controversy on the responsible mechanisms. The greatest controversy, by far, involves whether or not policy should involve a mandatory reduction in salt intake in all members of the community. The available evidence shows that the influence of salt intake is too inconsistent and generally too small to mandate policy decisions at the community level. At the level of the individual patient and that patient's physician, it is important to recognize that salt intake can make a substantial contribution to hypertension. That contribution is more likely if the patient is old rather than young, obese rather than lean, black rather than white, has diabetes mellitus with hypertension, or has evidence of renal injury. Unfortunately, tools for assessing the sodium and chloride intake in the individual and for assessing its contribution to BP in the individual are inadequate. On the bright side, prognosis is improved substantially by the array of antihypertensive drugs available today.

Hyperglycemia, excess weight, and history of hypertension as risk factors for poor outcome and cerebral infarction after aneurysmal subarachnoid hemorrhage

OBJECT

Stress-induced hyperglycemia has been shown to be associated with poor outcome after aneurysmal subarachnoid hemorrhage (SAH). The authors prospectively tested whether hyperglycemia, independent of other factors, affects patient outcomes and the occurrence of cerebral infarction after SAH.

METHODS

Previous diseases, health habits, medications, clinical condition, and neuroimaging variables were recorded for 175 patients with SAH who were admitted to the hospital within 48 hours after bleeding. The plasma level of glucose was measured at admission and the fasting value of glucose was measured in the morning after aneurysm occlusion. Factors found to be independently predictive of patient outcomes at 3 months after SAH onset and the appearance of cerebral infarction were tested by performing multiple logistic regression. Plasma glucose values at admission were found to be associated with patient age, body mass index (BMI), history of hypertension, clinical condition, amount of subarachnoid or intraventricular blood, shunt-dependent hydrocephalus, outcome variables, and the appearance of cerebral infarction. When considered independently of age, clinical condition, or amount of subarachnoid, intraventricular, or intracerebral blood, the plasma glucose values at admission predicted poor outcome (per millimole/liter the odds ratio [OR] was 1.24 with a 95% confidence interval [CI] of 1.02-1.51). After an adjustment was made for the amount of subarachnoid blood, the clinical condition, and the duration of temporary artery occlusion during surgery, the BMI was found to be a significant predictor (per kilogram/square meter the OR was 1.15 with a 95% CI of 1.02-1.29) for the finding of cerebral infarction on the follow-up computerized tomography scan. Hypertension (OR 3.11, 95% CI 1.11-8.73)--but not plasma glucose (OR 1.06, 95% CI 0.87-1.29)--also predicted the occurrence of infarction when tested instead of the BMI.

CONCLUSIONS

Independent of the severity of bleeding, hyperglycemia at admission seems to impair outcome, and excess weight and hypertension appear to elevate the risk of cerebral infarction after SAH.

Dietary salt restriction accelerates atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

Whether a general reduction in salt intake reduces or actually enhances cardiovascular mortality in man remains an issue of controversy. Low sodium diets may lead to adverse side effects by stimulating the renin-angiotensin and sympathetic nervous systems. The present study was designed to investigate the effects of low dietary salt on atherosclerotic lesion progression in apolipoprotein E deficient (apoE(-/-)) mice.

METHODS AND RESULTS

We fed 7-week-old apoE(-/-) mice on low (0.036% NaCl; n=28) or regular (0.64% NaCl; n=26) salt diets for 16 weeks. At the age of 23 weeks, the cross-section surface area of atherosclerotic plaques was measured in aortic root and thoracic aorta. Serum total cholesterol, triglycerides, plasma angiotensin levels and urinary protein/creatinine concentrations were assessed. Exposure to low salt caused significant increases in atherosclerotic lesion surface area in thoracic aorta, but did not alter lesion area in aortic root. Low-salt mice also had higher serum total cholesterol and higher plasma angiotensin II (ANG-II) concentrations. Atherosclerotic lesion area was correlated with ANG-II levels in low-salt but not in regular-salt animals, and with total cholesterol concentration in all mice. Mean arterial pressure was comparable in both groups.

CONCLUSIONS

Dietary salt restriction accelerated atherosclerotic lesion formation in apoE(-/-) mice through a mechanism that is probably related to ANG-II formation. Whether these findings are relevant to human cardiovascular disease remains to be evaluated.

Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride

BACKGROUND

One of the controversies in preventive medicine is, whether a general reduction in sodium intake can decrease the blood pressure of a population and thereby reduce cardiovascular mortality and morbidity. In recent years the debate has been extended by studies indicating that reducing sodium intake has effects on the hormone and lipid profile.

OBJECTIVES

To estimate the effects of low sodium versus high sodium intake on systolic and diastolic blood pressure (SBP and DBP), plasma or serum levels of renin, aldosterone, catecholamines, cholesterol and triglycerides.

SEARCH STRATEGY

"MEDLINE" and reference lists of relevant articles were searched from 1966 through December 2001.

SELECTION CRITERIA

Studies randomising persons to low sodium and high sodium diets were included if they evaluated at least one of the above outcome parameters.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data, which were analysed by means of Review Manager 4.1.

MAIN RESULTS

In 57 trials of mainly Caucasians with normal blood pressure, low sodium intake reduced SBP by -1.27 mm Hg (CI: -1.76; -0.77)(p<0.0001) and DBP by -0.54 mm Hg (CI: -0.94; -0.14) (p = 0.009) as compared to high sodium intake. In 58 trials of mainly Caucasians with elevated blood pressure, low sodium intake reduced SBP by -4.18 mm Hg (CI: -5.08; - 3.27) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -2.46; -1.32) (p < 0.0001) as compared to high sodium intake. The median duration of the intervention was 8 days in the normal blood pressure trials (range 4-1100) and 28 days in the elevated blood pressure trials (range 4-365). Multiple regression analyses showed no independent effect of duration on the effect size. In 8 trials of blacks with normal or elevated blood pressure, low sodium intake reduced SBP by -6.44 mm Hg (CI: -9.13; -3.74) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -4.75; 0.78) (p = 0.16) as compared to high sodium intake. The magnitude of blood pressure reduction was also greater in a single trial in Japanese patients. There was also a significant increase in plasma or serum renin, 304% (p < 0.0001), aldosterone, 322%, (p < 0.0001), noradrenaline, 30% (p < 0.0001), cholesterol, 5.4% (p < 0.0001) and LDL cholesterol, 4.6% (p < 0.004), and a borderline increase in adrenaline, 12% (p = 0.04) and triglyceride, 5.9% (p = 0.03) with low sodium intake as compared with high sodium intake.

REVIEWER'S CONCLUSIONS

The magnitude of the effect in Caucasians with normal blood pressure does not warrant a general recommendation to reduce sodium intake. Reduced sodium intake in Caucasians with elevated blood pressure has a useful effect to reduce blood pressure in the short-term. The results suggest that the effect of low versus high sodium intake on blood pressure was greater in Black and Asian patients than in Caucasians. However, the number of studies in black (8) and Asian patients (1) was insufficient for different recommendations. Additional long-term trials of the effect of reduced dietary sodium intake on blood pressure, metabolic variables, morbidity and mortality are required to establish whether this is a useful prophylactic or treatment strategy.

Dietary salt and hypertension: a scientific issue or a matter of faith?

Many workers have an overly simplistic view of the relationship between salt intake and hypertension. This article attempts a critical evaluation of some of the evidence.

Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride

BACKGROUND

One of the controversies in preventive medicine is, whether a general reduction in sodium intake can decrease the blood pressure of a population and thereby reduce cardiovascular mortality and morbidity. In recent years the debate has been extended by studies indicating that reducing sodium intake has effects on the hormone and lipid profile.

OBJECTIVES

To estimate the effects of low sodium versus high sodium intake on systolic and diastolic blood pressure (SBP and DBP), plasma or serum levels of renin, aldosterone, catecholamines, cholesterol and triglycerides.

SEARCH STRATEGY

"MEDLINE" and reference lists of relevant articles were searched from 1966 through December 2001.

SELECTION CRITERIA

Studies randomising persons to low sodium and high sodium diets were included if they evaluated at least one of the above outcome parameters.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data, which were analysed by means of Review Manager 4.1.

MAIN RESULTS

In 57 trials of mainly Caucasians with normal blood pressure, low sodium intake reduced SBP by -1.27 mm Hg (CI: -1.76; -0.77)(p<0.0001) and DBP by -0.54 mm Hg (CI: -0.94; -0.14) (p = 0.009) as compared to high sodium intake. In 58 trials of mainly Caucasians with elevated blood pressure, low sodium intake reduced SBP by -4.18 mm Hg (CI: -5.08; - 3.27) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -2.46; -1.32) (p < 0.0001) as compared to high sodium intake. The median duration of the intervention was 8 days in the normal blood pressure trials (range 4-1100) and 28 days in the elevated blood pressure trials (range 4-365). Multiple regression analyses showed no independent effect of duration on the effect size. In 8 trials of blacks with normal or elevated blood pressure, low sodium intake reduced SBP by -6.44 mm Hg (CI: -9.13; -3.74) (p < 0.0001) and DBP by -1.98 mm Hg (CI: -4.75; 0.78) (p = 0.16) as compared to high sodium intake. The magnitude of blood pressure reduction was also greater in a single trial in Japanese patients. There was also a significant increase in plasma or serum renin, 304% (p < 0.0001), aldosterone, 322%, (p < 0.0001), noradrenaline, 30% (p < 0.0001), cholesterol, 5.4% (p < 0.0001) and LDL cholesterol, 4.6% (p < 0.004), and a borderline increase in adrenaline, 12% (p = 0.04) and triglyceride, 5.9% (p = 0.03) with low sodium intake as compared with high sodium intake.

REVIEWER'S CONCLUSIONS

The magnitude of the effect in Caucasians with normal blood pressure does not warrant a general recommendation to reduce sodium intake. Reduced sodium intake in Caucasians with elevated blood pressure has a useful effect to reduce blood pressure in the short-term. The results suggest that the effect of low versus high sodium intake on blood pressure was greater in Black and Asian patients than in Caucasians. However, the number of studies in black (8) and Asian patients (1) was insufficient for different recommendations. Additional long-term trials of the effect of reduced dietary sodium intake on blood pressure, metabolic variables, morbidity and mortality are required to establish whether this is a useful prophylactic or treatment strategy.

Proposition of a feasible protocol to evaluate salt sensitivity in a population-based setting

Although a variety of techniques have been devised to assess salt sensitivity, most have proven cumbersome from a methodological perspective. We therefore attempted to develop a 2-week method by which participants could be tested in an outpatient setting without requirement of a strict dietary regimen. In this method, subjects take 140 mEq of an NaCl supplement per day for 1 week and 25 mg of hydrochlorothiazide daily for another week while maintaining their customary diet. In our first trial, 8 healthy volunteers submitted to this method, as well as to a widely-used rapid volume expansion and contraction protocol. Blood pressure measurements, blood sampling and 24-h urine collection were performed before, in the middle of, and after each intervention. There was a fair correlation (r = 0.69) between the two protocols with respect to the changes in mean blood pressure (deltaMBP), a measure of salt sensitivity. In our second trial, we tested the method on 82 Japanese subjects who had never been treated with antihypertensive drugs. DeltaMBP was significantly correlated with plasma renin activity (PRA) during salt loading (r = 0.52, p < 0.0001) and with the changes in atrial natriuretic peptide (deltaANP) (r = -0.34, p = 0.0018). When total subjects were divided into two subgroups by age, a similar tendency of correlation was observed. Age, PRA during salt loading, deltaANP, and delta norepinephrine were proven to be significant predictors of salt sensitivity and accounted for 46% of the deltaMBP variances. Based on these results, the dietary method presented here seems to be applicable for a population-based survey. Our preliminary data also suggest that PRA and ANP would be of predictive value in the salt sensitivity test.

Biobehavioral approaches to the treatment of essential hypertension

Despite recent advances in the medical management of hypertension, chronically elevated blood pressure remains a major health problem in the United States, affecting almost 50 million Americans. It is widely recognized that lifestyle factors contribute to the development and maintenance of elevated blood pressure. This article critically reviews current approaches to the nonpharmacological treatment of high blood pressure and highlights outcome studies of exercise, weight loss and dietary modification, and stress management and relaxation therapies. Methodological issues in the assessment and treatment of hypertension are discussed, along with possible mechanisms by which lifestyle modification may reduce elevated blood pressure.

Nutritional factors in the control of blood pressure and hypertension

Differing hypertension prevalence rates between certain population and age groups are partially due to differences in the intake of certain nutrients. Blood pressure is positively associated with higher sodium, alcohol, and protein intakes; it is inversely associated with potassium, calcium, and magnesium intakes. Salt may lead to an increase in blood pressure in the presence of salt sensitivity, but there is no inexpensive or easy strategy to identify salt-sensitive patients. Other risk factors for hypertension include obesity and lack of regular physical activity. The best strategy appears to be moderate salt restriction (6-7 g/day) in combination with an optimal compliance of the antihypertensive drug therapy, as well as adoption of the combination diet of the DASH study--a diet rich in fruits and vegetables, and thus rich in potassium. Current evidence does not support the increased intake of Ca2+ or Mg2+ for blood-pressure-lowering purposes only; however, calcium and magnesium may represent important components in the combination diet of the DASH study. It seems that it is the combination of these nutrients that is of crucial importance for the achievement of optimal blood-pressure reduction. Also recommended is a decrease in alcohol consumption and an increase in regular physical activity. Instead of a severe intervention with regard to 1 risk factor alone, positive changes in 5 habits combined--high salt intake, high sodium-to-potassium ratio, alcohol intake, calorie imbalance, and a sedentary life--may be the most realistic and effective strategy to counteract the present hypertension epidemic.

Effect of potassium supplementation on blood pressure in Chinese: a randomized, placebo-controlled trial

OBJECTIVE

To examine the effect of potassium supplementation on blood pressure (BP) in a Chinese population who consume a habitual high sodium and low potassium diet.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Community sample from Beijing, China.

PARTICIPANTS

A total of 150 men and women aged 35-64 years with an initial systolic BP 130-159 mmHg and/or diastolic BP 80-94 mmHg.

INTERVENTIONS

Participants were randomly assigned to take 60 mmol potassium chloride supplement or placebo for 12 weeks.

MAIN OUTCOME MEASURE(S)

BP measurements were obtained at baseline, and at 6 weeks and 12 weeks during the trial, using random-zero sphygmomanometers.

RESULTS

The average baseline urinary excretion of sodium and potassium was 182 mmol/24 h and 36 mmol/24 h. Baseline BP and other measured variables were similar between the potassium supplementation and placebo groups. In the active compared to the placebo treatment group, the urinary excretion of potassium was significantly increased by 20.6 mmol/24 h (P< 0.001) during 12 weeks of intervention. Compared to placebo, active treatment was associated with a significant reduction in systolic BP (-5.00 mmHg, 95% CI: -2.13 to -7.88 mmHg, P < 0.001) but not diastolic BP (-0.63 mmHg, 95% CI: -2.49 to1.23 mmHg, P = 0.51) during 12-week intervention.

CONCLUSION

These data indicate that moderate potassium supplementation resulted in a substantial reduction in systolic BP. Our findings suggest that increased potassium intake may play an important role in the prevention and treatment of hypertension in China.

Salt and blood pressure. Conventional wisdom reconsidered

The salt hypothesis is that higher levels of salt in the diet lead to higher levels of blood pressure, increasing the risk of cardiovascular disease. Intersalt, a cross-sectional study of salt levels and blood pressures in 52 populations, is often cited to support the salt hypothesis, but the data are somewhat contradictory. Four of the populations (Kenya, Papua, and 2 Indian tribes in Brazil) do have low levels of salt and blood pressure. Across the other 48 populations, however, blood pressures go down as salt levels go up, contradicting the hypothesis. Experimental evidence suggests that the effect of a large reduction in salt intake on blood pressure is modest, and health consequences remain to be determined. Funding agencies and medical journals have taken a stronger position favoring the salt hypothesis than is warranted, raising questions about the interaction between the policy process and science.

Leisure-time physical activity and other factors in relation to blood pressure in Japanese-Americans in Hawaii, USA

To examine physical activity at work and during leisure-time as well as other factors related to blood pressure (BP) in Japanese-Americans living in Hilo, Hawaii, USA, we performed a population-based cross-sectional study with a sample of 238 participants aged 42-64 years old. This survey was carried out between 19 February and 1 March 2000 in Hilo. All participants were invited to Hilo Medical Center for a free physical examination and experimental tests including an examination of blood and urine samples. A self-administered health questionnaire was used that included items related to demographics, smoking, alcohol consumption, and habitual physical activity at work and during leisure-time. A summary score of physical activity (PA) was calculated. BP was measured using an automated BP measurement system (Khi machine, VINE Co., Ltd., Kyoto, Japan). The results showed the following. 1) Mean (SD) PA scores at work (WPA) and during leisure-time (LTPA) were 2.9 (0.5) and 2.5 (0.5) in men, and 3.0 (0.5) and 2.4 (0.3) in women, respectively; 2) Pearson correlation analyses (adjustment for age) indicated that WPA and LTPA in men show significant negative associations with SBP and DBP (p<0.05 and p<0.01), while LTPA shows significant negative associations with SBP and DBP in women (p<0.05 and p<0.01). After further adjustment for education, occupation, smoking, and alcohol consumption status, LTPA continued to show significant and negative associations with both SBP and DBP in men (p<0.01) and with DBP alone in women (p <0.01). 3) Hypertensive subjects had significantly lower mean LTPA scores than normotensive men (2.39 vs. 2.61, p<0.05) and women (2.32 vs. 2.45, p<0.05). 4) Body mass index and the ratio of sodium to potassium excretion showed significant and positive associations with SBP and DBP in multiple linear regression analyses. In conclusion, the results further emphasize that the health benefits of LTPA, control of body weight, and reduction in salt intake should continually receive strong attention in population-based high BP control.

The dietary guideline for sodium: should we shake it up? No

The current US dietary guideline for sodium is a limit of 2.4 g/d or 6 g NaCl/d. This amount of sodium is far in excess of any physiologic need and is likely an essential though not by itself sufficient primary cause of hypertension as well as a contributor to many other cardiovascular and renal abnormalities. The evidence incriminating the current excessive consumption of sodium derives from epidemiologic, experimental, and interventional data, most of which support a threshold of approximately 100 mmol/d for the harmful effects of sodium to be expressed. Although the current recommendation may not be low enough to go below that threshold, it is an appropriate and attainable goal for now.

Dietary salt reduction in hypertension--what is the evidence and why is it still controversial?

The link between sodium intake and hypertension remains controversial because of inconsistency between early epidemiologic studies, which showed a strong positive relationship between salt intake and blood pressure/incidence of hypertension, and more recent studies, which showed only modest decreases in blood pressure with sodium reduction, particularly in the normotensive population. In addition, there is clinical evidence that sodium is related to target organ damage such as left ventricular hypertrophy and renal disease. Although the evidence available linking sodium intake and blood pressure in the general population is weak, sodium reduction has been shown to be useful in hypertensive patients, particularly salt-sensitive patients. Whether dietary sodium reduction should be recommended for the general population remains questionable because of marginal benefit and the suggestion of possible deleterious effects on cardiovascular outcomes independent of blood pressure. This paper will review the definition and methods used in determining salt sensitivity, the evidence linking sodium intake and target organ damage, and modern studies of salt and blood pressure.

Lifestyle modifications to prevent and control hypertension. 6. Recommendations on potassium, magnesium and calcium. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada

OBJECTIVE

To provide updated, evidence-based recommendations on the consumption, through diet, and supplementation of the cations potassium, magnesium and calcium for the prevention and treatment of hypertension in otherwise healthy adults (except pregnant women).

OPTIONS

Dietary supplementation with cations has been suggested as an alternative or adjunctive therapy to antihypertensive medications. Other options include other nonpharmacologic treatments for hypertension.

OUTCOMES

The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

A MEDLINE search was conducted for the period 1966-1996 with the terms hypertension and potassium, magnesium and calcium. Reports of trials, meta-analyses and review articles were obtained. Other relevant evidence was obtained from the reference lists of articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design, and graded according to the level of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS, HARMS AND COSTS

The weight of the evidence from randomized controlled trials indicates that increasing intake of or supplementing the diet with potassium, magnesium or calcium is not associated with prevention of hypertension, nor is it effective in reducing high blood pressure. Potassium supplementation may be effective in reducing blood pressure in patients with hypokalemia during diuretic therapy.

RECOMMENDATIONS

For the prevention of hypertension, the following recommendations are made: (1) The daily dietary intake of potassium should be 60 mmol or more, because this level of intake has been associated with a reduced risk of stroke-related mortality. (2) For normotensive people obtaining on average 60 mmol of potassium daily through dietary intake, potassium supplementation is not recommended as a means of preventing an increase in blood pressure. (3) For normotensive people, magnesium supplementation is not recommended as a means of preventing an increase in blood pressure. (4) For normotensive people, calcium supplementation above the recommended daily intake is not recommended as a means of preventing an increase in blood pressure. For the treatment of hypertension, the following recommendations are made. (5) Potassium supplementation above the recommended daily dietary intake of 60 mmol is not recommended as a treatment for hypertension. (6) Magnesium supplementation is not recommended as a treatment for hypertension. (7) Calcium supplementation above the recommended daily dietary intake is not recommended as a treatment for hypertension.

VALIDATION

These guidelines are consistent with the results of meta-analyses and recommendations made by other organizations. They have not been clinically tested.

SPONSORS

The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.