Misinformation surrounding sodium reduction for blood pressure: content analysis of Japanese posts on X

This content analysis aimed to assess misinformation themes regarding sodium reduction and blood pressure on X with the goal of providing strategies to address and debunk such misinformation. A total of 531 posts were manually coded into sodium-related misinformation themes, with inclusion criteria for posts asserting no association between sodium reduction and hypertension or claiming consuming sodium is beneficial for health. Numbers and post frequencies per misinformation theme were calculated. Post characteristics, including information sources, advertisements and narratives, were coded, and a correlation analysis was conducted to assess their association with each misinformation theme. Fourteen sodium-related misinformation themes were identified and consistently disseminated on X. The predominant theme, 'Natural Salt', accounted for 37.7% (n = 200), reaching 1.6 million followers, followed by 'Reducing salt could be bad for my health' theme, comprising 28.6% (n = 152) and reaching 1.5 million followers. There was a statistical correlation between the natural salt misinformation theme and advertisements. Many of the most frequent misinformation themes identified in this study have not been systematically debunked by organizations such as the World Health Organization and the American Heart Association. This study underscores the importance of continuous monitoring and analysis of sodium-related misinformation on social media platforms and their underlying commercial interests. Such monitoring has the potential to identify prevalent misinformation themes that may pose harm to the public and to inform public health organizations, enabling them to proactively address potential issues through debunking.

Screening for hypertension in adults: protocol for evidence reviews to inform a Canadian Task Force on Preventive Health Care guideline update

PURPOSE

To inform updated recommendations by the Canadian Task Force on Preventive Health Care on screening in a primary care setting for hypertension in adults aged 18 years and older. This protocol outlines the scope and methods for a series of systematic reviews and one overview of reviews.

METHODS

To evaluate the benefits and harms of screening for hypertension, the Task Force will rely on the relevant key questions from the 2021 United States Preventive Services Task Force systematic review. In addition, a series of reviews will be conducted to identify, appraise, and synthesize the evidence on (1) the association of blood pressure measurement methods and future cardiovascular (CVD)-related outcomes, (2) thresholds for discussions of treatment initiation, and (3) patient acceptability of hypertension screening methods. For the review of blood pressure measurement methods and future CVD-related outcomes, we will perform a de novo review and search MEDLINE, Embase, CENTRAL, and APA PsycInfo for randomized controlled trials, prospective or retrospective cohort studies, nested case-control studies, and within-arm analyses of intervention studies. For the thresholds for discussions of treatment initiation review, we will perform an overview of reviews and update results from a relevant 2019 UK NICE review. We will search MEDLINE, Embase, APA PsycInfo, and Epistemonikos for systematic reviews. For the acceptability review, we will perform a de novo systematic review and search MEDLINE, Embase, and APA PsycInfo for randomized controlled trials, controlled clinical trials, and observational studies with comparison groups. Websites of relevant organizations, gray literature sources, and the reference lists of included studies and reviews will be hand-searched. Title and abstract screening will be completed by two independent reviewers. Full-text screening, data extraction, risk-of-bias assessment, and GRADE (Grading of Recommendations Assessment, Development and Evaluation) will be completed independently by two reviewers. Results from included studies will be synthesized narratively and pooled via meta-analysis when appropriate. The GRADE approach will be used to assess the certainty of evidence for outcomes.

DISCUSSION

The results of the evidence reviews will be used to inform Canadian recommendations on screening for hypertension in adults aged 18 years and older.

SYSTEMATIC REVIEW REGISTRATION

This protocol is registered on PROSPERO and is available on the Open Science Framework (osf.io/8w4tz).

A candidate locus in the renalase gene and susceptibility to blood pressure responses to the dietary salt

BACKGROUND

High dietary salt confers a risk of elevating blood pressure (BP) and the development of hypertension. BP to salt intake may be determined in part by individual genetic predisposition. Identifying these genetic underpinnings will enhance our understanding of the biological mechanisms of BP regulation. This study aims to assess the genetic association with salt sensitivity of BP (SSBP) within two well-phenotyped multinational cohorts.

METHODS

A total of 720 white participants from the HyperPATH consortium program were selected and genotyped using a multiethnic genotyping array. Individuals consumed two study diets containing high (>200 mEq/day) and low (<10 mEq/day) sodium content, after which SSBP, aldosterone, and plasma renin activity (PRA) were assessed in a controlled inpatient research setting.

RESULTS

A top signal (rs10887801; beta = 4.57, P  = 5.03E - 07) at the renalase gene ( RNLS ) region was significantly associated with SSBP. We also identified seven single nucleotide variants with linkage disequilibrium to the top signal at this region that comprised a significant haplotype (TCTTAGTT, P  = 0.00081). Homozygous carriers of the T-risk allele of the key single nucleotide variant had higher SSBP ( P  ≤ 0.00001) and lower PRA ( P  = 0.0076) compared with the nonrisk allele.

CONCLUSION

We identified significant associations between genetic variants of the RNLS gene and BP responses to dietary salt intervention and PRA that suggest susceptibility to volume-driven hypertension. These findings may contribute to a better understanding of the genetic mechanisms underlying BP regulation, support the role of RNLS in the pathogenesis of SSBP, and identify individuals who may be at risk from excess dietary salt intake.

The interaction effects of secondhand smoke exposure and overweight on the prevalence of hypertension in Chinese coke oven workers and NHANES participants (2013-2016)

BACKGROUND

The prevalence of hypertension may be affected by environmental pollution and personal behavior.

OBJECTIVES

We aimed to evaluate the interaction effects of secondhand smoke exposure and overweight on hypertension.

METHODS

In this cross-sectional study, a total of 627 workers from a coking plant in China and 1011 individuals from the NHANES database in the United States from 2013 to 2016 were selected as the research participants. The concentrations of 11 urinary polycyclic aromatic hydrocarbons (PAHs) metabolites and 3 tobacco metabolites were measured. An interaction effect was tested in the modified Poisson regression models.

RESULTS

For smokers among Chinese coke oven workers, the only statistically significant positive association was with hypertension in the highest tertile of nicotine metabolized ratio (NMR) (PR: 1.539, 95% CI: 1.013-2.337). Nonsmoking Chinese workers with 3rd tertile urinary nicotine levels were associated with a 114.8% significantly increased prevalence of hypertension (PR: 2.148, 95% CI: 1.025-4.500) compared to nonsmokers 1st tertile with nicotine levels. Association between tobacco exposure and hypertension is possibly modified by PAHs exposure (PR: 2.335, 95% CI: 0.933-5.841). Nonsmokers in the NHANES database with high urinary nicotine levels were associated with a 17.3% significantly increased prevalence of hypertension (PR: 1.173, 95% CI: 1.028-1.338) compared to those with low nicotine levels. We observed that overweight people with high nicotine levels had a significantly higher likelihood of hypertension than no overweight people with low nicotine levels among nonsmoking Chinese coke oven workers and NHANES participants (PR = 4.686, 95% CI: 1.488-14.754; PR = 1.251, 95% CI: 1.039-1.506).

CONCLUSIONS

Tobacco exposure and overweight are important risk factors for hypertension, and secondhand smoke exposure and overweight have an interactive effect on the incidence of hypertension in nonsmoking Chinese coke oven workers and NHANES participants.

Cold Pressor Test in Primary Hypertension: A Cross-Sectional Study

Objectives

To investigate the characteristics of patients with primary hypertension who had positive responses to the cold pressor test (CPT).

Methods

This cross-sectional study was conducted between November 2018 to November 2019, and the CPT was performed in patients with primary hypertension in 48 hospitals. The demographic characteristics and complications were collected through a questionnaire and physical examinations. A 12-month follow-up was conducted to identify the occurrence of the following events: a) all-cause mortality; b) myocardial infarction; c) stroke; d) hospitalized for heart failure.

Results

The CPT was positive in 30.7% of the patients. Compared with the negative CPT group, the positive CPT group was associated with a lower rate of blood pressure control, and was more likely to have a high salt diet, diabetes, hyperuricemia, left ventricular wall thickening, carotid plaques, coronary heart disease and heart failure. A high-salt diet (OR = 1.228, 95%CI: 1.037–1.456) was found to be correlated with the positive result of CPT. Among patients in the positive CPT group, those using diuretics had a significantly higher rate of blood pressure control than those not using diuretics (54.6 vs.42.6%, x² = 6.756, P = 0.009). After a 12-month follow-up, the incidence of heart failure in the positive CPT group was significantly higher than that in the negative CPT group (7.35 vs.5.01%, x² = 3.945, P = 0.047).

Conclusions

Patients with positive responses to the CPT had lower rates of BP control and a high risk of heart failure, which may be related to their preference for a high-salt diet. The use of diuretics helps to better control blood pressure in those patients.

Salt: The paradoxical philosopher's stone of autonomic medicine

Sodium chloride, or common table salt, for millennia has played a prominent role in human affairs. Salt is also a key molecule for regulating intravascular fluid volume in patients with orthostatic disorders. In this first article of a special issue of the journal focusing on salt and the autonomic nervous system, the historical and physiologic significance of salt is reviewed, highlighting its importance to society and to medicine. The relevance of salt both for civilization and for autonomic physiology penetrates into nearly every aspect of life and health. Replacing salt that has been depleted or administering salt to expand intravascular volume is considered standard treatment for patients with orthostatic hypotension and syndromes of orthostatic intolerance. The potential longterm effects of added salt, including effects unrelated to intravascular volume, have been insufficiently studied in patients with autonomic disorders. A salient concern is the potential increased risk of developing hypertension. Underappreciated aspects of salt include its ability to increase anxiety and through nonosmotic mechanisms to contribute to local tissue inflammation. Salt may be either salubrious or detrimental, or possibly both at the same time, depending on the clinical conditions. Reconciling these opposite effects in clinical practice requires weighing benefits against potential risks, assessing what is known alongside what is uncertain, and titrating treatment decisions to the particular needs of each individual patient.

Socio-demographic factors in relation to habitual sodium and potassium intakes among adults in Trinidad and Tobago

BACKGROUND

Approximately one-third of adults in Trinidad and Tobago have high blood pressure (hypertension). Excessive consumption of sodium (Na⁺) is a known risk factor for hypertension.

AIM

We investigated Na⁺ and potassium (K⁺) intakes and their correlates in a multi-ethnic Caribbean population.

METHOD

Volunteers completed a self-administered questionnaire comprising socio-demographic items, physical activity (PA) and a semiquantitative food frequency questionnaire. Foods eaten were classified by level of processing using the NOVA classification system and analysed for Na⁺ and K⁺ levels using appropriate dietary analysis software. The study was approved by the University of the West Indies at Saint Augustine Ethics Committee.

RESULTS

11,783 adults participated in the study. Approximately 83.2% of total calories, 79% of Na⁺ and 40% of K⁺ was derived from the consumption of highly processed foods. Median daily Na⁺ and K⁺ intakes were 2759 mg and 2853 mg, respectively. Na⁺ intakes showed significant nonlinear increases with age (p < 0.001) and body mass index (BMI) (p < 0.001), and non-linear decreases with educational attainment (p < 0.001). K⁺ intakes showed significant nonlinear decreases with age (p < 0.001) and BMI (p < 0.001), and linear increases with educational attainment (p < 0.001). Males had higher intakes of Na⁺ and K⁺ than females. Na⁺: K⁺ was lower among persons participating in moderate to high intensity PA ≥ 150 minutes/week compared to those participating in such activities < 150 minutes/week.

CONCLUSION

Socio-demographic factors were significantly correlated with Na⁺ and K⁺ intakes among participants and must be considered in strategies aimed at achieving healthy intakes of these nutrients.

Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake

Several blood pressure guidelines recommend low sodium intake (<2.3 g/day, 100 mmol, 5.8 g/day of salt) for the entire population, on the premise that reductions in sodium intake, irrespective of the levels, will lower blood pressure, and, in turn, reduce cardiovascular disease occurrence. These guidelines have been developed without effective interventions to achieve sustained low sodium intake in free-living individuals, without a feasible method to estimate sodium intake reliably in individuals, and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with moderate intake). In this review, we examine whether the recommendation for low sodium intake, reached by current guideline panels, is supported by robust evidence. Our review provides a counterpoint to the current recommendation for low sodium intake and suggests that a specific low sodium intake target (e.g. <2.3 g/day) for individuals may be unfeasible, of uncertain effect on other dietary factors and of unproven effectiveness in reducing cardiovascular disease. We contend that current evidence, despite methodological limitations, suggests that most of the world's population consume a moderate range of dietary sodium (2.3-4.6g/day; 1-2 teaspoons of salt) that is not associated with increased cardiovascular risk, and that the risk of cardiovascular disease increases when sodium intakes exceed 5 g/day. While current evidence has limitations, and there are differences of opinion in interpretation of existing evidence, it is reasonable, based upon observational studies, to suggest a population-level mean target of <5 g/day in populations with mean sodium intake of >5 g/day, while awaiting the results of large randomized controlled trials of sodium reduction on incidence of cardiovascular events and mortality.

The global epidemiology of hypertension

Hypertension is the leading cause of cardiovascular disease and premature death worldwide. Owing to the widespread use of antihypertensive medications, global mean blood pressure (BP) has remained constant or has decreased slightly over the past four decades. By contrast, the prevalence of hypertension has increased, especially in low- and middle-income countries (LMICs). Estimates suggest that 31.1% of adults (1.39 billion) worldwide had hypertension in 2010. The prevalence of hypertension among adults was higher in LMICs (31.5%, 1.04 billion people) than in high-income countries (28.5%, 349 million people). Variations in the levels of risk factors for hypertension, such as high sodium intake, low potassium intake, obesity, alcohol consumption, physical inactivity and unhealthy diet, may explain some of the regional heterogeneity in hypertension prevalence. Despite the increasing prevalence, the proportions of hypertension awareness, treatment and BP control are low, particularly in LMICs, and few comprehensive assessments of the economic impact of hypertension exist. Future studies are warranted to test implementation strategies for hypertension prevention and control, especially in low-income populations, and to accurately assess the prevalence and financial burden of hypertension worldwide.

Dose-response association of dietary sodium intake with all-cause and cardiovascular mortality: a systematic review and meta-analysis of prospective studies

OBJECTIVE

High Na intake has been associated with different health problems. However, serious controversies exist over studies investigating associations of Na intake with mortality from all-causes and CVD. The present systematic review and meta-analysis was done to investigate, for the first time, the dose-response association of dietary Na intake with all-cause and CVD mortality among prospective studies.

DESIGN

Relevant papers published up to August 2017 were searched in MEDLINE, EMBASE and Google Scholar databases. Prospective cohort studies on the association of dietary Na intake with all-cause or/and CVD mortality were included. Linear and non-linear dose-response associations between Na intake and CVD and all-cause mortality were examined.

RESULTS

Overall, twenty publications met inclusion criteria. A significant non-linear association (P&lt;0·001) was found between Na intake and CVD mortality risk among studies assessing urinary Na excretion, with a relatively steep slope at Na intakes above 2400mg/d. However, the association was not significant in studies using dietary Na intake (P=0·61). Additionally, the non-linear association of Na intake with all-cause mortality was also non-significant. No linear association (effect size; 95 % CI; I 2) was seen between 100mg/d increment in Na intake and CVD mortality (1·01; 0·97, 1·05; 98·4 %) or all-cause mortality (1·01; 1·00, 1·02; 89·2 %). Following subgroup analyses, the association between Na intake and CVD mortality was observed only among studies conducted in the USA (0·99; 0·99, 1·00; 20·0 %).

CONCLUSIONS

The study showed a direct association between urinary Na excretion and CVD mortality which was more considerable at intakes above 2400mg/d. In contrast, no significant association was found between Na intake and all-cause mortality. Further long-term prospective studies on different populations are required to confirm these findings.

The technical report on sodium intake and cardiovascular disease in low- and middle-income countries by the joint working group of the World Heart Federation, the European Society of Hypertension and the European Public Health Association

Ingestion of sodium is essential to health, but excess sodium intake is a risk factor for hypertension and cardiovascular disease. Defining an optimal range of sodium intake in populations has been challenging and controversial. Clinical trials evaluating the effect of sodium reduction on blood pressure have shown blood pressure lowering effects down to sodium intake of less than 1.5 g/day. Findings from these blood pressure trials form the basis for current guideline recommendations to reduce sodium intake to less than 2.3 g/day. However, these clinical trials employed interventions that are not feasible for population-wide implementation (i.e. feeding studies or intensive behavioural interventions), particularly in low and middle-income countries. Prospective cohort studies have identified the optimal range of sodium intake to reside in the moderate range (3-5 g/day), where the risk of cardiovascular disease and death is lowest. Therefore, there is consistent evidence from clinical trials and observational studies to support reducing sodium intake to less than 5 g/day in populations, but inconsistent evidence for further reductions below a moderate intake range (3-5 g/day). Unfortunately, there are no large randomized controlled trials comparing low sodium intake (< 3 g/day) to moderate sodium intake (3-5 g/day) in general populations to determine the net clinical effects of low sodium intake. Until such trials are completed, it is likely that controversy about optimal sodium intake range will continue. This working group calls for the completion of large definitive clinical trials to clarify the range of sodium intake for optimal cardiovascular health within the moderate to low intake range. We support interventions to reduce sodium intake in populations who consume high sodium intake (> 5 g/day), which should be embedded within an overall healthy dietary pattern.

Reduced dietary salt for the prevention of cardiovascular disease

BACKGROUND

This is an update of a Cochrane review that was first published in 2011 of the effects of reducing dietary salt intake, through advice to reduce salt intake or low-sodium salt substitution, on mortality and cardiovascular events.

OBJECTIVES

1. To assess the long-term effects of advice and salt substitution, aimed at reducing dietary salt, on mortality and cardiovascular morbidity.2. To investigate whether a reduction in blood pressure is an explanatory factor in the effect of such dietary interventions on mortality and cardiovascular outcomes.

SEARCH METHODS

We updated the searches of CENTRAL (2013, Issue 4), MEDLINE (OVID, 1946 to April week 3 2013), EMBASE (OVID, 1947 to 30 April 2013) and CINAHL (EBSCO, inception to 1 April 2013) and last ran these on 1 May 2013. We also checked the references of included studies and reviews. We applied no language restrictions.

SELECTION CRITERIA

Trials fulfilled the following criteria: (1) randomised, with follow-up of at least six months, (2) the intervention was reduced dietary salt (through advice to reduce salt intake or low-sodium salt substitution), (3) participants were adults and (4) mortality or cardiovascular morbidity data were available. Two review authors independently assessed whether studies met these criteria.

DATA COLLECTION AND ANALYSIS

A single author extracted data and assessed study validity, and a second author checked this. We contacted trial authors where possible to obtain missing information. We extracted events and calculated risk ratios (RRs) and 95% confidence intervals (CIs).

MAIN RESULTS

Eight studies met the inclusion criteria: three in normotensives (n = 3518) and five in hypertensives or mixed populations of normo- and hypertensives (n = 3766). End of trial follow-up ranged from six to 36 months and the longest observational follow-up (after trial end) was 12.7 years.The risk ratios (RR) for all-cause mortality in normotensives were imprecise and showed no evidence of reduction (end of trial RR 0.67, 95% confidence interval (CI) 0.40 to 1.12, 60 deaths; longest follow-up RR 0.90, 95% CI 0.58 to 1.40, 79 deaths n=3518) or in hypertensives (end of trial RR 1.00, 95% CI 0.86 to 1.15, 565 deaths; longest follow-up RR 0.99, 95% CI 0.87 to 1.14, 674 deaths n=3085). There was weak evidence of benefit for cardiovascular mortality (hypertensives: end of trial RR 0.67, 95% CI 0.45 to 1.01, 106 events n=2656) and for cardiovascular events (hypertensives: end of trial RR 0.76, 95% CI 0.57 to 1.01, 194 events, four studies, n = 3397; normotensives: at longest follow-up RR 0.71, 95% CI 0.42 to 1.20, 200 events; hypertensives: RR 0.77, 95% CI 0.57 to 1.02, 192 events; pooled analysis of six trials RR 0.77, 95% CI 0.63 to 0.95, n = 5912). These findings were driven by one trial among retirement home residents that reduced salt intake in the kitchens of the homes, thereby not requiring individual behaviour change.Advice to reduce salt showed small reductions in systolic blood pressure (mean difference (MD) -1.15 mmHg, 95% CI -2.32 to 0.02 n=2079) and diastolic blood pressure (MD -0.80 mmHg, 95% CI -1.37 to -0.23 n=2079) in normotensives and greater reductions in systolic blood pressure in hypertensives (MD -4.14 mmHg, 95% CI -5.84 to -2.43 n=675), but no difference in diastolic blood pressure (MD -3.74 mmHg, 95% CI -8.41 to 0.93 n=675).Overall many of the trials failed to report sufficient detail to assess their potential risk of bias. Health-related quality of life was assessed in one trial in normotensives, which reported significant improvements in well-being but no data were presented.

AUTHORS' CONCLUSIONS

Despite collating more event data than previous systematic reviews of randomised controlled trials, there is insufficient power to confirm clinically important effects of dietary advice and salt substitution on cardiovascular mortality in normotensive or hypertensive populations. Our estimates of the clinical benefits from advice to reduce dietary salt are imprecise, but are larger than would be predicted from the small blood pressure reductions achieved. Further well-powered studies would be needed to obtain more precise estimates. Our findings do not support individual dietary advice as a means of restricting salt intake. It is possible that alternative strategies that do not require individual behaviour change may be effective and merit further trials.

High-salt intake induces cardiomyocyte hypertrophy in rats in response to local angiotensin II type 1 receptor activation

Many studies have shown that risk factors that are independent of blood pressure (BP) can contribute to the development of cardiac hypertrophy (CH). Among these factors, high-salt (HS) intake was prominent. Although some studies have attempted to elucidate the role of salt in the development of this disease, the mechanisms by which salt acts are not yet fully understood. Thus, the aim of this study was to better understand the mechanisms of CH and interstitial fibrosis (IF) caused by HS intake. Male Wistar rats were divided into 5 groups according to diet [normal salt (NS; 1.27% NaCl) or HS (8% NaCl)] and treatment [losartan (LOS) (HS+LOS group), hydralazine (HZ) (HS+HZ group), or N-acetylcysteine (NAC) (HS+NAC group)], which was given in the drinking water. Tail-cuff BP, transverse diameter of the cardiomyocyte, IF, angiotensin II type 1 receptor (AT1) gene and protein expression, serum aldosterone, cardiac angiotensin II, cardiac thiobarbituric acid-reactive substances, and binding of conformation-specific anti-AT1 and anti-angiotensin II type 2 receptor (AT2) antibodies in the 2 ventricles were measured. Based on the left ventricle transverse diameter data, the primary finding was the occurrence of significant BP-independent CH in the HS+HZ group (96% of the HS group) and a partial or total prevention of such hypertrophy via treatment with NAC or LOS (81% and 67% of the HS group, respectively). The significant total or partial prevention of IF using all 3 treatments (HS+HZ, 27%; HS+LOS, 27%; and HS+NAC, 58% of the HS group, respectively), and an increase in the AT1 gene and protein expression and activity in groups that developed CH, confirmed that CH occurred via the AT1 in this experimental model. Thus, this study unveiled some relevant previously unknown mechanisms of CH induced by chronic HS intake in Wistar rats. The link of oxidative stress with CH in our experimental model is very interesting and stimulates further evaluation for its full comprehension.

Daily sodium consumption and CVD mortality in the general population: systematic review and meta-analysis of prospective studies

OBJECTIVE

The purpose of the present study was to determine whether elevated dietary Na intake could be associated with CVD mortality.

DESIGN

We performed a systematic review and meta-analysis of prospective studies representing the general population. The adjusted relative risks and their 95 % confidence intervals were pooled by the inverse variance method using random-effects models. Heterogeneity, publication bias, subgroup and meta-regression analyses were performed. Settings MEDLINE (since 1973), Embase (since 1975), the Cochrane Library (since 1976), ISI Web of Science, Google Scholar (until September 2013) and secondary referencing were searched for inclusion in the study. Subject Eleven prospective studies with 229 785 participants and average follow-up period of 13.37 years (range 5.5-19 years).

RESULTS

Higher Na intake was significantly associated with higher CVD mortality (relative risk=1.12; 95 % CI 1.06, 1.19). In the sensitivity analysis, the exclusion of studies with important relative weights did not significantly affect the results (relative risk=1.08; 95 % CI 1.01, 1.15). The meta-regression analysis showed that for every increase of 10 mmol/d in Na intake, CVD mortality increased significantly by 1 % (P=0.016). Age, hypertensive status and length of follow-up were also associated with increased CVD mortality.

CONCLUSIONS

Higher Na intake was associated with higher CVD mortality in the general population; this result suggests a reduction in Na intake to prevent CVD mortality from any cause.

Common genetic variants in the endothelial system predict blood pressure response to sodium intake: the GenSalt study

BACKGROUND We examined the association between 14 endothelial system genes and salt-sensitivity of blood pressure (BP). METHODS After a 3-day baseline examination, during which time the usual diet was consumed, 1,906 Chinese participants received a 7-day low-sodium diet (51.3 mmol of sodium/day) followed by a 7-day high-sodium diet (307.8 mmol of sodium/day). BP measurements were obtained at baseline and at the end of each intervention using a random-zero sphygmomanometer. RESULTS The DDAH1 rs11161637 variant was associated with reduced BP salt sensitivity, conferring attenuated systolic BP (SBP) and mean arterial pressure (MAP) decreases from baseline to the low-sodium intervention (both P = 2×10(-4)). Examination of genotype-sex interactions revealed that this relation was driven by the strong associations observed in men (P for interactions = 1.10×10(-4) and 0.008, respectively). When switching from the low- to high-sodium intervention, increases in diastolic BP (DBP) and MAP were attenuated by the COL18A1 rs2838944 minor A allele (P = 1.41×10(-4) and 1.55×10(-4), respectively). Conversely, the VWF rs2239153 C variant was associated with increased salt sensitivity, conferring larger DBP and MAP reductions during low-sodium intervention (P = 1.22×10(-4) and 4.44×10(-5), respectively). Ten variants from 3 independent SELE loci displayed significant genotype-sex interactions on DBP and MAP responses to low-sodium (P for interaction = 1.56×10(-3) to 1.00×10(-4)). Among men, minor alleles of 4 correlated markers attenuated BP responses to low-sodium intake, whereas minor alleles of another 4 correlated markers increased BP responses. No associations were observed in women for these variants. Further, qualitative interactions were shown for 2 correlated SELE markers. CONCLUSIONS These data support a role for the endothelial system genes in salt sensitivity.

Spot urine tests in predicting 24-hour urine sodium excretion in Asian patients

OBJECTIVE

The control of hypertension is often suboptimal, and it is frequently due to excessive sodium intake. Monitoring sodium intake is cumbersome and involves 24-hour collection of urine. We hypothesize that a spot urine test can accurately predict 24-hour urine sodium excretion in an Asian population.

DESIGN

This is a prospective, observational study. We used stored urine specimens (n = 333) from the Asian Kidney Disease Study and Singapore Kidney Function Study Phase I. We measured spot urine tests and correlated these variables to the previously measured 24-hour urine sodium measurements.

RESULTS

Age, gender, ethnicity, diastolic blood pressure, height, weight, body mass index, serum creatinine, spot urine sodium, spot urine chloride, and spot urine osmolality were associated with 24-hour urine sodium excretion. The final model for predicting 24-hour urine sodium less than 100 mmol included age, gender, ethnicity, weight, and spot urine sodium.

CONCLUSION

Spot urine sodium can help monitor a patient's sodium intake when used in the derived 5-variable equation.

Analysis of sex hormone genes reveals gender differences in the genetic etiology of blood pressure salt sensitivity: the GenSalt study

BACKGROUND

We examined the association between 799 single-nucleotide polymorphisms in 39 sex hormone genes and blood pressure (BP) responses to a dietary-sodium intervention.

METHODS

A 7-day low-sodium feeding study (51.3 mmol sodium/day) followed by a 7-day high-sodium feeding study (307.8 mmol sodium/day) was conducted among 1,906 Han Chinese participants. Nine BP measurements were obtained at baseline and the end of each intervention period using a random-zero sphygmomanometer.

RESULTS

Among men, absolute BP responses to sodium interventions decreased with the number of minor alleles of estrogen receptor 1 (ESR1) markers rs9340844, rs9397453, rs9371562, rs9397459, and rs9383951. For example, mean diastolic blood pressure (DBP) responses to low-sodium intervention (95% confidence interval) were -2.67 (-3.13, -2.22) mm Hg among those with the rs9397453 C/C genotype, -1.23 (-1.98, -0.48) mm Hg among those with the C/T genotype, and 0.08 (-2.31, 2.47) mm Hg among those with the T/T genotype (P = 1×10(-4); false discovery rate (FDR)-q = 0.04). Mean DBP responses to high sodium according to the rs9397453 genotypes were 1.46 (1.03, 1.89) mm Hg among those with C/C, 0.19 (-0.54, 0.91) mm Hg among those with C/T, and -1.10 (-2.82, 0.61) mm Hg among those with T/T (P = 2×10(-4); FDR-q = 0.04). Similar trends were noted for the association between these ESR1 variants and SBP responses to the dietary intervention. There were no significant associations between sex hormone gene variants and salt sensitivity in women, with genotype-gender interactions noted for the ESR1 markers that achieved significance in men.

CONCLUSIONS

We identified strong, consistent associations between ESR1 gene variants and salt sensitivity in men. Our results support a gender-specific role for ESR1 in the etiology of this complex trait.

Genomic epidemiology of blood pressure salt sensitivity

High blood pressure (BP) is a complex trait determined by genetic and environmental factors, as well as their interactions. Over the past few decades, there has been substantial progress elucidating the genetic determinants underlying BP response to sodium intake, or BP salt sensitivity. Research of monogenic BP disorders has highlighted the importance of renal salt handling in BP regulation, implicating genes and biological pathways subsequently identified in candidate gene studies of salt sensitivity. Despite these advancements, certain candidate gene findings await replication evidence, and some biological pathways warrant further investigation. Furthermore, results from genome-wide association studies (GWASs) and sequencing work have yet to be reported. GWAS will be valuable for uncovering novel mechanisms underlying salt sensitivity, whereas future sequencing efforts promise the discovery of functional variants related to this complex trait. Delineating the genetic architecture of salt sensitivity will be critical to understanding how genes and dietary sodium interact to influence BP.

Gene-sodium interaction and blood pressure: findings from genomics research of blood pressure salt sensitivity

High blood pressure (BP) is a complex trait determined by both genetic and environmental factors, as well as the interactions between these factors. Over the past few decades, there has been substantial progress in elucidating the genetic determinants underlying the BP response to sodium intake, or BP salt sensitivity. Research of monogenic BP disorders has highlighted the importance of renal salt handling in BP regulation, implicating genes and biological pathways related to salt sensitivity. Candidate gene studies have contributed important information toward understanding the genomic mechanisms underlying the BP response to salt intake, identifying genes in the renin-angiotensin-aldosterone system, renal sodium channels/transporters, and the endothelial system related to this phenotype. Despite these advancements, genome-wide association studies are still needed to uncover novel mechanisms underlying salt sensitivity, while future sequencing efforts promise the discovery of functional variants related to this complex trait. Delineating the genetic architecture of salt sensitivity will be critical to understanding how genes and dietary sodium interact to influence BP.

Reduced dietary salt for the prevention of cardiovascular disease: a meta-analysis of randomized controlled trials (Cochrane review)

BACKGROUND

Although meta-analyses of randomized controlled trials (RCTs) of salt reduction report a reduction in the level of blood pressure (BP), the effect of reduced dietary salt on cardiovascular disease (CVD) events remains unclear.

METHODS

We searched for RCTs with follow-up of at least 6 months that compared dietary salt reduction (restricted salt dietary intervention or advice to reduce salt intake) to control/no intervention in adults, and reported mortality or CVD morbidity data. Outcomes were pooled at end of trial or longest follow-up point.

RESULTS

Seven studies were identified: three in normotensives, two in hypertensives, one in a mixed population of normo- and hypertensives and one in heart failure. Salt reduction was associated with reductions in urinary salt excretion of between 27 and 39 mmol/24 h and reductions in systolic BP between 1 and 4 mm Hg. Relative risks (RRs) for all-cause mortality in normotensives (longest follow-up-RR: 0.90, 95% confidence interval (CI): 0.58-1.40, 79 deaths) and hypertensives (longest follow-up RR 0.96, 0.83-1.11, 565 deaths) showed no strong evidence of any effect of salt reduction CVD morbidity in people with normal BP (longest follow-up: RR 0.71, 0.42-1.20, 200 events) and raised BP at baseline (end of trial: RR 0.84, 0.57-1.23, 93 events) also showed no strong evidence of benefit. Salt restriction increased the risk of all-cause mortality in those with heart failure (end of trial RR 2.59, 1.04-6.44, 21 deaths).We found no information on participant's health-related quality of life.

CONCLUSIONS

Despite collating more event data than previous systematic reviews of RCTs (665 deaths in some 6,250 participants) there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or CVD morbidity. Our estimates of benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small BP reduction achieved.

Salt-induced cardiac hypertrophy and interstitial fibrosis are due to a blood pressure-independent mechanism in Wistar rats

High salt intake is a known cardiovascular risk factor and is associated with cardiac alterations. To better understand this effect, male Wistar rats were fed a normal (NSD: 1.3% NaCl), high 4 (HSD4: 4%), or high 8 (HSD8: 8%) salt diet from weaning until 18 wk of age. The HSD8 group was subdivided into HSD8, HSD8+HZ (15 mg . kg(-1) . d(-1) hydralazine in the drinking water), and HSD8+LOS (20 mg . kg(-1) . d(-1) losartan in the drinking water) groups. The cardiomyocyte diameter was greater in the HSD4 and HSD8 groups than in the HSD8+LOS and NSD groups. Interstitial fibrosis was greater in the HSD4 and HSD8 groups than in the HSD8+HZ and NSD groups. Hydralazine prevented high blood pressure (BP) and fibrosis, but not cardiomyocyte hypertrophy. Losartan prevented high BP and cardiomyocyte hypertrophy, but not fibrosis. Angiotensin II type 1 receptor (AT(1)) protein expression in both ventricles was greater in the HSD8 group than in the NSD group. Losartan, but not hydralazine, prevented this effect. Compared with the NSD group, the binding of an AT(1) conformation-specific antibody that recognizes the activated form of the receptor was lower in both ventricles in all other groups. Losartan further lowered the binding of the anti-AT(1) antibody in both ventricles compared with all other experimental groups. Angiotensin II was greater in both ventricles in all groups compared with the NSD group. Myocardial structural alterations in response to HSD are independent of the effect on BP. Salt-induced cardiomyocyte hypertrophy and interstitial fibrosis possibly are due to different mechanisms. Evidence from the present study suggests that salt-induced AT(1) receptor internalization is probably due to angiotensin II binding.

Twelve-year trends and correlates of dietary salt intakes for the general adult population of Geneva, Switzerland

BACKGROUND/OBJECTIVES

Investigate dietary salt intake trends by gender, and their associations with risk factors for cardiovascular diseases in Geneva, Switzerland.

SUBJECTS/METHODS

Continuous surveillance of the Geneva general adult (35-74 years) population for 12 years (1993-2004) using a validated, semi-quantitative food frequency questionnaire (FFQ) in random, cross-sectional, representative samples (6688 men, 6647 women). Dietary salt intake assessment by FFQ excluded discretionary salt, but was calibrated on total salt intake using an independent validation substudy of 100 volunteers who additionally provided 24-h urine collections.

RESULTS

Quartiles (mean) of calibrated dietary salt intake (g per day) were 9.9, 10.5, 11.2 (10.6) in men, and 7.0, 7.8, 8.9 (8.1) in women and were above current recommendations. Quartiles (mean) of salt density (g MJ(-1)) were 0.99, 1.16, 1.39 (1.23) in men, and 0.98, 1.12, 1.30 (1.17) in women. Both measures were stable during the 12-year surveillance period, regardless of hypertension treatment. Salt-density differences between cardiovascular disease risk factor subgroups were moderate. Salt density increased with age and body mass index. The main dietary non-discretionary salt food sources (men/women: 47/48%) were breads (17/17%), cheeses (11/10%), meat and meat products (8/7%), soups (6/9%) and ready-to-eat foods (5/5%).

CONCLUSIONS

Salt intakes from all sources for the Geneva, and perhaps the Swiss adult population are above current recommendations. The quantitative and qualitative data provided in this paper could be used to develop and implement strategies for salt-intake reduction in Switzerland.

Salt and Blood Pressure: Time to Challenge

Hypertension is a worldwide epidemic and its control is costly, but still inadequate. The mechanisms underlying the development of primary hypertension remain elusive. Several observations point to the kidney as a primary actor and sodium as the main culprit for development of hypertension. Over the last few decades, experimental, observational and clinical data have continuously indicated that excess salt intake is positively associated with elevated blood pressure and that blood pressure can be significantly reduced with substantial reductions in dietary sodium. This review highlights the pathophysiological mechanisms linking sodium to elevated blood pressure, synthesizes available evidence for the effect of reducing salt intake in controlling blood pressure. It specifically analyzes 6 recent meta-analyses and dietary approaches to stop hypertension.

Links between dietary salt intake, renal salt handling, blood pressure, and cardiovascular diseases

Epidemiological, migration, intervention, and genetic studies in humans and animals provide very strong evidence of a causal link between high salt intake and high blood pressure. The mechanisms by which dietary salt increases arterial pressure are not fully understood, but they seem related to the inability of the kidneys to excrete large amounts of salt. From an evolutionary viewpoint, the human species is adapted to ingest and excrete <1 g of salt per day, at least 10 times less than the average values currently observed in industrialized and urbanized countries. Independent of the rise in blood pressure, dietary salt also increases cardiac left ventricular mass, arterial thickness and stiffness, the incidence of strokes, and the severity of cardiac failure. Thus chronic exposure to a high-salt diet appears to be a major factor involved in the frequent occurrence of hypertension and cardiovascular diseases in human populations.