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

Epidemiology of risk factors for hypertension: implications for prevention and therapy

We review the present knowledge of risk factors for arterial hypertension. Both genetic and environmental factors as well as their interaction and biological plausibility are reviewed. Recent data confirm that the interaction of genetics with multiple environmental risk factors explains the high prevalence of hypertension in the industrialised countries. The most important modifiable environmental risk factors are high salt intake, alcohol intake, obesity and low physical activity. The role of stress in the aetiology of high blood pressure is still under investigation, but recent clinical experimental and epidemiological data have shed light on how stress could be related to hypertension. The implications for prevention and treatment are discussed both at the population and individual levels. The population approach involves a public health policy aiming at modification of the major risk factors. The individual approach involves nonpharmacological measures to prevent the development of hypertension and to treat high normal blood pressure and mild hypertension with no additional cardiovascular risk factors. Pharmacological treatment of hypertension in most individuals should use agents that have been proven to be effective in randomised controlled trials with 'hard' endpoints such as cardiovascular and cerebrovascular morbidity and mortality.

What is the role of dietary sodium and potassium in hypertension and target organ injury?

There is substantial evidence from both observational epidemiology studies and randomized controlled trials that dietary intake of sodium and potassium is important in the etiology of hypertension. However, the direct evidence for a direct link between dietary sodium and potassium and risk of cardiovascular and renovascular events is limited. Epidemiological studies should be designed to examine the relationship between dietary intake of sodium and potassium and risk of stroke, coronary heart disease, left ventricular hypertrophy, and renal disease in a prospective manner. In these studies, dietary intake of sodium and potassium should be estimated using multiple 24-hour urine collections. These studies should be focused on African Americans because they are at a disproportionately high risk of developing hypertension and blood pressure-related vascular disease. Moreover, this group has been underrepresented in most previous epidemiological studies.

Salt sensitivity: concept and pathogenesis

Almost two decades ago, the existence of a subset of essential hypertensive patients, who were sensitive (according to the increase in blood pressure levels) to the intake of a diet with a high salt content, was described. These patients are characterized by an increase in blood pressure and in body weight when switched from a low to a high sodium intake. The increase in body weight is due to the incapacity of the kidneys to excrete the whole intake of sodium until renal perfusion pressure (mean blood pressure) attains a level that is able to restore pressure-natriuresis relationship to values that enable the kidney to excrete the salt ingested or administered intravenously. Salt sensitivity does not seem to depend on the existence of an intrinsic renal defect to handle sodium, but on the existence of subtle abnormalities in the regulation of the sympathetic nervous system, the renin-angiotensin system or endothelial function. It is also relevant that organ damage secondary to arterial hypertension, has been shown in animal models and in hypertensive humans sensitive to a high salt intake to be significantly higher when compared with that of salt-resistant animals or humans. Interestingly, in humans, salt sensitivity has been shown to correlate with microalbuminuria, an important predictor of cardiovascular morbidity and mortality, which correlates with most of the cardiovascular risk factors commonly associated with arterial hypertension. One of these factors is insulin resistance, that usually accompanies high blood pressure in overweight and obese hypertensives. Insulin resistance and hyperinsulinism are present in a significant percentage of hypertensive patients developing cardiovascular symptoms or death. For these reasons, therapy of arterial hypertension must be directed, not only to facilitate the lowering of BP level, but also, to halt the mechanisms underlying the increase in BP, when salt intake is increased. Furthermore, therapy must preferably improve the diminished insulin sensitivity present in salt-sensitive subjects that contribute independently to increased cardiovascular risk.

Short-term effects of dietary sodium intake on bone metabolism in postmenopausal women measured using urinary deoxypyridinoline excretion

The influence of Na load on bone metabolism was investigated in postmenopausal women using urinary deoxypyridinoline (DPD) as a marker of bone resorption. In a cross-over study, fourteen postmenopausal women were divided into two groups of seven. A fixed diet providing 816 mg Ca/d with either 60 or 170 mmol Na/d was consumed. At the end of an 8 d period the groups switched diets for a further 8 d period. Urine was collected daily for the last 4 d of each period. There was no significant difference in DPD excretion between high-Na and low-Na diets (129 nmol/d v. 132 nmol/d; P = 0.18). There was, however, a significant relationship (P = 0.02) between the changes in DPD excretion and urinary Ca. Plasma Mg fell from 0.83 to 0.81 mmol/l on the high Na intake (P < 0.001), but there was no significant effect on plasma Ca or intact parathyroid hormone levels. It is concluded that varying dietary Na intake may affect Ca and Mg metabolism, but we were unable to demonstrate an effect on bone resorption at the levels of intake used.

Life style as a blood pressure determinant

In Belgium, an affluent Western European country, participation in sports, alcohol intake, and living in a working class area were identified as the life style factors with the closest associations with the blood pressure level. Obesity was another important blood pressure correlate. Sodium intake, determined from the 24 h urinary output, and smoking were not associated with blood pressure. Controlled intervention studies have proven that weight reduction, endurance training and alcohol abstinence effectively reduce blood pressure. In the light of these intervention studies, the Belgian findings and the published work highlight the potential of preventive strategies aimed at these major life style factors.

Role of angiotensinogen in the genetics of essential hypertension

Although essential hypertension has long been recognized to involve a strong genetic predisposition, the genes that increase susceptibility remain virtually unknown. With recent advances in molecular biology and statistical methods, it has become feasible to study candidate genes which may contribute to the pathogenesis of essential hypertension in humans. Recently, the angiotensinogen (AGT) locus was demonstrated to exhibit genetic linkage and association to essential hypertension and to preeclampsia. While the statistical evidence that mutations of the AGT gene or a neighboring gene contribute to the development of hypertension is strong, the exact mechanism(s) by which these mutations affect the regulation of blood pressure (BP) is unknown. Increasing attention is now being focused on elucidating this mechanism(s).

Risk factors for spontaneous intracerebral hemorrhage

BACKGROUND AND PURPOSE

Spontaneous intracerebral hemorrhage has remained a serious disease despite recent improvements in medical treatment. This study was designed to identify modifiable risk factors for intracerebral hemorrhage.

METHODS

Health habits, previous diseases, and medication of 156 consecutive patients with intracerebral hemorrhage aged 16 to 60 years (96 men and 60 women) were compared with those of 332 hospitalized control patients (192 men and 140 women) who did not differ from case subjects in respect to age, day of onset of symptoms, or acuteness of disease onset.

RESULTS

After adjustment for sex, age, hypertension, body mass index, smoking status, and alcohol consumption during the last week, patients who had consumed 1 to 40, 41 to 120, or > 120 g of alcohol within the 24 hours preceding the onset of illness had a relative risk (95% confidence interval) of hemorrhage of 0.3 (0.2 to 0.7), 4.6 (2.2 to 9.4), and 11.3 (3.0 to 42.8), respectively, compared with those who had consumed 0 g. In addition, alcohol intake within 1 week before the onset of illness, excluding use within the last 24 hours, increased the risk of hemorrhage; adjusted risks were 2.0 (1.1 to 3.5) for 1 to 150 g, 4.3 (1.6 to 11.7) for 151 to 300 g, and 6.5 (2.4 to 17.7) for > 300 g compared with 0 g. The adjusted risk of hypertension for hemorrhage was 6.6 (3.9 to 11.3). Previous heavy alcohol consumption and current cigarette smoking were not independent risk factors for hemorrhage, but anticoagulant treatment was (P < .01). Erythrocyte mean corpuscular volume and gamma-glutamyl transferase values were also higher in patients with intracerebral hemorrhage than in control subjects.

CONCLUSIONS

Recent moderate and heavy alcohol intake as well as hypertension and likely also anticoagulant treatment seem to be independent risk factors for intracerebral hemorrhage.

Reduction of salt intake during converting enzyme inhibitor treatment compared with addition of a thiazide

A moderate reduction in salt intake lowers blood pressure in individuals with hypertension and improves blood pressure control in those taking a converting enzyme inhibitor. However, it is unclear how effective reduction of salt intake is compared with addition of other drugs, in particular, thiazide diuretics. We directly compared the separate effects on blood pressure of reducing sodium intake or adding a thiazide diuretic in the pressure of a converting enzyme inhibitor in a double-blind, randomized, crossover study. We studied 11 subjects with essential hypertension who had been taking 25 mg captopril twice daily for at least 1 month. In the double-blind study, after 1 month of captopril alone, supine blood pressure was 151 +/- 5/95 +/- 4 (SEM) mm Hg. With the addition of 25 mg hydrochlorothiazide once daily for 1 month, blood pressure fell to 137 +/- 5/87 +/- 3 mm Hg. When a moderate reduction in salt intake (from 206 +/- 26 to 109 +/- 20 mmol urinary sodium/24 h) was added to captopril for 1 month, blood pressure was reduced by a similar amount (to 137 +/- 4/90 +/- 3 mm Hg). Plasma potassium fell during the diuretic treatment (3.9 +/- 0.1 to 3.7 +/- 0.1 mmol/L, P < .05) but increased nonsignificantly during salt reduction (3.9 +/- 0.1 to 4.1 +/- 0.2 mmol/L). These results clearly demonstrate that moderate salt reduction, which can be easily achieved, is as effective as a thiazide diuretic in lowering blood pressure in the presence of a converting enzyme inhibitor and has the particular advantage that plasma potassium does not decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertension, coronary artery disease and insulin resistance--linked disorders with an impact on treatment

Coronary artery disease is a very common disorder for which hypertension is a well-recognized risk factor. However many trials of antihypertensive therapy have failed to demonstrate a reduction in the incidence of coronary events. One explanation is that hypertension is a disorder associated with hyperinsulinaemia, obesity and non-insulin dependent diabetes. Furthermore certain antihypertensive drugs, notably thiazide diuretics, increase the hyperinsulinaemia and thereby increase one of the other coronary risk factors. In this review the links between hypertension and hyperinsulinaemia are explored and the mechanisms whereby an increased plasma insulin can lead to the more rapid development of coronary artery disease are explained. These observations may influence the choice of drugs used to treat hypertension.

Alcohol and hypertension

The relationship between regular alcohol consumption and blood pressure elevation is now firmly established. Outstanding issues which will be discussed relate to the nature of the dose response curve, interactions between alcohol and other dietary and behavioural factors, mechanisms involved and the question of any protective influence of alcohol on atherosclerotic and ischaemic cardiovascular disease associated with hypertension. Alcohol is an important contributory to the prevalence of hypertension, and resistance to drug therapy in drinking communities. Heavy drinking and binge drinking increases the risk of stroke.

Minerals and blood pressure

The mineral elements sodium, potassium, calcium and magnesium play a central role in the normal regulation of blood pressure. In particular, these mineral elements have important interrelationships in the control of arterial resistance. These elements, especially sodium and potassium, also regulate the fluid balance of the body and, hence, influence the cardiac output. Evidence shows that the present levels of intake of mineral elements are not optimum for maintaining normal blood pressure but predispose to the development of arterial hypertension. Research results suggest that without sodium chloride (common salt) and other sodium compounds being added to the diet arterial hypertension would be virtually non existent. Moreover, blood pressure would not rise with age. In communities with a high consumption of added sodium, a high intake of potassium and, possibly, magnesium seem to protect against the development of arterial hypertension and the rise of blood pressure with age. A marked reduction of sodium intake is effective in treating even severe hypertension. A moderate restriction of sodium intake or an increase in potassium intake exert remarkable antihypertensive effects, at least in some hypertensive patients. Magnesium and possibly also calcium supplements may be effective in reducing blood pressure in some hypertensives. In hypertensive patients treated with drugs sodium restriction and potassium and magnesium supplementation enhance the therapeutic effect, reduce the number and dosage, and lessen the adverse effects of prescribed antihypertensive drugs. Hence, a fall in sodium consumption and increases in potassium and magnesium consumption are useful in preventing and treating arterial hypertension.

Sodium restriction in hypertensive patients treated with a converting enzyme inhibitor and a thiazide

When the function of the renin system is inhibited, blood pressure becomes more dependent on changes in sodium and water balance. Diuretics alone and sodium restriction alone are additive to converting enzyme inhibitor therapy. However, it is not known if these two ways of reducing sodium balance are additive in the presence of established converting enzyme inhibition. We therefore performed a double-blind crossover study of the effects of moderate sodium restriction in 21 patients with essential hypertension who were already being treated with the combination of a converting enzyme inhibitor and a diuretic. After 1 month of captopril (50 mg twice daily) and hydrochlorothiazide (25 mg once daily) therapy, with their usual sodium intake, average supine blood pressure was 147/96 +/- 5/3 (SEM) mm Hg 2 hours after treatment. Patients then reduced their sodium intake to around 80-100 mmol/day for the remainder of the study. After 2 weeks of sodium restriction, they entered a double-blind, randomized, crossover study of Slow Sodium (100 mmol sodium/day) compared with Slow Sodium placebo, while continuing sodium restriction and the above treatment. During the double-blind study, after 1 month of treatment with captopril (50 mg twice daily), hydrochlorothiazide (25 mg once daily), and Slow Sodium placebo, supine blood pressure 2 hours after treatment was 138/88 +/- 4/2 mm Hg (24-hour urinary sodium 104 +/- 11 mmol). After 1 month of captopril (50 mg twice daily), hydrochlorothiazide (25 mg once daily), and Slow Sodium tablets, supine blood pressure 2 hours after treatment was 147/91 +/- 5/2 mm Hg (p less than 0.05; 24-hour urinary sodium 195 +/- 14 mmol).(ABSTRACT TRUNCATED AT 250 WORDS)

By how much does dietary salt reduction lower blood pressure? II--Analysis of observational data within populations

OBJECTIVE

To determine whether the estimates of the size of the association between blood pressure and sodium intake derived from studies of individuals within populations can be quantitatively reconciled with our estimates derived from comparisons of the average blood pressure and sodium intake between different populations.

DESIGN

Examination of data from 14 published studies that correlated blood pressure recordings in individuals against measurements of their 24 hour sodium intake (within population studies).

MAIN OUTCOME MEASURE

Comparison of observed differences in blood pressure per 100 mmol/24 h difference in sodium intake in each within population study with predicted differences calculated from the between population data, after allowing for the underestimation of the true association of blood pressure with sodium intake caused by the large day to day variation in 24 hour sodium intake within individuals.

RESULTS

The underestimation bias inherent in the within populations studies reduced the regression slope of blood pressure on single measures of 24 hour sodium intake to between a half and a quarter of the true value (for example, in one study from 6.0 to 2.4 mm Hg/100 mmol/24 h). Estimates from between population comparisons of the regression slope of blood pressure on sodium intake, after adjustment to take this underestimation bias into account, were similar to the values actually observed in the within population studies.

CONCLUSION

The within population studies confirm our estimates from between population comparisons of the magnitude of the association between blood pressure and sodium intake.

Nutrition and blood pressure among elderly men and women (Dutch Nutrition Surveillance System)

Associations between blood pressure and nutrition-related variables (body mass index, dietary intake, and 24-hr excretion of sodium, potassium, magnesium, and calcium in the urine) were investigated in men (n = 138) and women (n = 117) 65-79 years old not using drugs known to affect blood pressure and not on a diet. Among men, body mass index was positively and creatinine clearance was inversely associated with systolic blood pressure, whereas body mass index and urinary sodium:potassium ratio were positively associated with diastolic blood pressure. Among women, both age and urinary calcium:creatinine ratio were positively associated with systolic as well as diastolic blood pressure. Coffee consumption was positively correlated with blood pressure and urinary calcium:creatinine ratio among the women. From the results it appears that, besides "normal" weight, increased potassium intake and urinary excretion may exert a protective effect among elderly men against hypertension when sodium exposure is relatively high. The positive association between urinary calcium:creatinine ratio and blood pressure among the women may be partly due to coffee consumption.

Two-way factorial study of alcohol and salt restriction in treated hypertensive men

The aim of this study was to determine whether moderate restriction of dietary salt intake leads to an additional fall in blood pressure in treated hypertensive men who are asked to simultaneously reduce their usual alcohol intake. Sixty-three subjects entered an initial 2-week familiarization period during which they continued their usual alcohol intake and commenced a "low sodium" diet (less than 60 mmol/day) supplemented with 100 mmol sodium chloride per day as enteric-coated tablets. Subjects were then randomly assigned to either drink a low alcohol beer alone for a 4-week period (reducing their self-reported alcohol consumption from 537 to 57 ml/week) or to continue their usual alcohol intake (543 versus 557 ml/week). Within the low and normal alcohol intake groups, subjects were assigned to either a low or normal sodium intake. The low sodium groups continued the sodium-restricted diet but were switched to placebo sodium chloride tablets for the 4 weeks. This resulted in a fall in the 24-hour urinary sodium excretion from 144 to 69 mmol/day. The normal sodium groups continued the low sodium diet but kept taking 100 mmol/day of the sodium chloride tablets, and their urinary sodium excretion remained unchanged (125 versus 142 mmol/day). Regular antihypertensive therapy was continued throughout. Fifty-nine subjects completed the trial. In those who reduced their alcohol intake there was a fall in both systolic blood pressure (-5.4 mm Hg supine, p less than 0.01) and diastolic blood pressure (-3.2 mm Hg supine, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Blood pressure and relative body weight, alcohol consumption and electrolyte excretion in the FRG and the GDR: the Intersalt Study. The Intersalt Study Group form the FRG and the GDR]

The relationships between body mass index (BMI) and age, alcohol consumption, 24-hr urinary electrolyte excretion, and BP were studied in 588 subjects from three German centers participating in Intersalt, a highly standardized, previously reported protocol. Men and women aged 20-59 were sampled in Bernried, FRG; Cottbus, GDR; and Heidelberg, FRG. The subjects from the three centers did not differ in BMI, level of education, physical activity, cigarette- or alcohol-consumption patterns, or urinary Cl excretion. Mean Na excretion was 167, 147, and 172 mmol/24 hr in Bernried, Cottbus, and Heidelberg, while mean K excretion was 72, 55, and 73 mmol/24 hr, respectively. The excretion of these electrolytes was significantly lower in Cottbus than in Bernried or Heidelberg. BMI increased progressively in men with age; in women BMI plateaued until the 5th decade, after which it increased to equal that of men. In individual centers, the excretion of electrolytes was correlated with BMI. Sodium and chloride excretion were highly correlated. The data from each individual center were fitted to a multiple regression model. Age, BMI, sex, and alcohol consumption entered the model.

Effects of non-pharmacologic therapy

Whereas there is no doubt that non-drug treatment of hypertension, and modifications in life-style to prevent an age-associated rise in arterial pressure are attractive concepts, opinions vary as to what advice should be offered to hypertensive patients and to populations at large. No modification in diet or life style has been demonstrated to reduce the complications of hypertension. Review of recent reports suggests that moderate exercise, weight reduction in the obese, and moderation of alcohol intake are usually effective in reducing arterial pressure and are unaccompanied by adverse effects. On the contrary, restriction of dietary sodium, or supplementation with potassium, calcium or magnesium have little or variable antihypertensive effects, are not readily accepted by a high percentage of the population, and could have adverse consequences. Other dietary modifications may reduce blood pressure, but additional research is needed to define the relevant component in the diet.

Concomitants of excess coronary deaths--major risk factor and lifestyle findings from 10,359 men and women in the Scottish Heart Health Study

The Scottish Heart Health Study is a study of lifestyle and coronary heart disease risk factors in 10,359 men and women aged 40-59 years, in 22 districts of Scotland. The study was conducted during 1984-86, when Scotland had the highest national coronary heart disease mortality reported by the World Health Organisation. A self-completed questionnaire, complemented by a 40 minute visit to a survey clinic, staffed by nurses, enabled the classical major risk factors and some more newly described ones to be measured. The study emphasised quality control and representativeness, and incorporated a World Health Organisation protocol for measurement of key items to allow comparisons in place and time, and therefore also to provide a definitive baseline against which interventions can be assessed. This paper describes the overall findings. Current cigarette smokers constitute 39% of men and 38% of women, higher levels than those reported in England but lower than previous Scottish reports. Mean blood pressure levels were 134/84 mmHg for men and 131/81 mmHg in women, lower than in British studies of the 1960s and 1970s. Mean body mass index levels, 26.1 Kg/m2 in men and 25.7 Kg/m2 in women, were not high by international standards. However, mean serum cholesterol levels were 6.4 mmol/l in men and 6.6 mmol/l in women--as high as those in previous British studies and high by international standards. Levels of high density lipoprotein cholesterol, non-fasting triglycerides and fibrinogen are also reported. Physical activity both at work and in leisure time was low.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of changing dietary sodium on the airway response to histamine

The airway response to histamine has been shown to be related to the 24 hour urinary excretion of sodium. To assess whether this relation is likely to represent a direct causal association a randomised double blind crossover trial of slow sodium (80 mmol/day) was compared with placebo in 36 subjects having a low sodium diet. The dose of histamine causing a 20% fall in FEV1 (PD20) was 1.51 doubling doses lower when the men were taking sodium than when they were taking placebo (p less than 0.05). On the basis of PD10 values, the difference in men was 1.66 doubling doses of histamine (p less than 0.05). There was no corresponding effect in women. Regressing PD10 against urinary excretion of electrolytes with data from the two occasions during the trial and the measurements made before the trial showed a significant association with sodium excretion after allowance had been made for any effect associated with potassium or creatinine excretion, the latter being a marker of the completeness of the urine collection. Again there was no corresponding effect among women. These findings are compatible with the differences in regional mortality data for England and Wales, which show a relation between asthma mortality and regional per person purchases of table salt for men but not for women.