Can dietary changes reduce blood pressure in the long term?

Miura K, Nakagawa H.

Department of Epidemiology and Public Health, Kanazawa Medical University, Ishikawa, Japan.

PURPOSE OF REVIEW: Recent dietary guidelines for the prevention and treatment of hypertension emphasized a healthy eating pattern called the Dietary Approaches to Stop Hypertension (DASH) diet, in addition to avoidance of obesity, high salt intake, and excessive alcohol intake. Our new challenge is to examine the long-term efficacy and effectiveness of dietary change, including the DASH diet, on blood pressure in the general population, or in a high-risk population. We reviewed recent short-term and long-term studies, both observational and interventional, which investigated whether dietary change can reduce blood pressure. RECENT FINDINGS: The efficacy of several nutrients has been investigated in short-term trials (e.g. polyunsaturated fatty acids, including omega-3 fatty acids, and trans fatty acids), but no substantial effect of these nutrients on blood pressure has been proved, except for dietary fiber. The PREMIER trial showed the effectiveness of implementing the DASH diet for 6 months in addition to the established recommendations on lifestyle modification, but other long-term trials of dietary modification did not show sufficient blood pressure reduction. However, long-term observational studies have shown that a higher intake of fruit and vegetables and a lower intake of red meat (except fish) can prevent higher blood pressure increase with age. SUMMARY: More effective programs of dietary modification are needed to achieve greater reduction of blood pressure. Long-term studies of population-wide dietary interventions to decrease the blood pressure level of a whole population are also needed.

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Early life determinants of adult blood pressure.

Lawlor DA, Smith GD.

Department of Social Medicine, University of Bristol, Bristol, UK.

PURPOSE OF REVIEW: While treating high blood pressure in middle age is beneficial in terms of reducing the occurrence of cardiovascular disease, treated and well controlled hypertensive adults still have a substantial excess mortality and reduced survival compared with normotensives. Therefore, identification of the means of preventing hypertension in earlier life is an important objective. There is increasing evidence that adult blood pressure is determined by a range of characteristics from the intrauterine period, through infancy and childhood. The purpose of this review is to provide a summary of the current evidence concerning the early life determinants of adult blood pressure. RECENT FINDINGS: Children from poorer socioeconomic positions, those whose mothers experience pregnancy-induced hypertension, those whose mothers smoke throughout pregnancy, those with low birthweight, who are not breast-fed, who have high sodium diets in infancy and who are obese in childhood or adolescence tend to have higher blood pressure in adulthood. However, the mechanisms linking these early life factors to later blood pressure and the most appropriate means of preventing adult hypertension by intervening in early life are unclear. SUMMARY: There is clear evidence that early life factors are important determinants of adult blood pressure. However, there is a need for randomized trials with sufficient resources for long-term follow-up to assess the effects that interventions such as preventing pregnancy-induced hypertension, reducing maternal smoking, increasing breast-feeding, reducing salt consumption in infancy and preventing childhood obesity have on adult blood pressure and cardiovascular disease.

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Blood pressure variability: its measurement and significance in hypertension.

Parati G.

Department of Clinical Medicine, Prevention and Applied Biotechnology, University of Milano-Bicocca, Cardiology II, S. Luca Hospital, IRCCS, Istituto Auxologico Italiano, and Centro Interuniversitario di Fisiologia Clinica e Ipertensione, Milan, Italy.

The occurrence of blood pressure fluctuations over time has been documented since the 18th century, but the clinical importance of this phenomenon is only now being recognized. The introduction of ambulatory blood pressure monitoring in the late 1960s represented a major step forward in the study of blood pressure behaviour and helped to characterize the relationship between blood pressure variability and cardiovascular disease. In hypertension, blood pressure variability increases with increasing blood pressure and correlates closely with target-organ damage, independently of absolute blood pressure values. This has important consequences for treatment, which in the past has focused on reducing mean blood pressure values as the main goal. Experimental evidence suggests that drugs capable of buffering or reducing blood pressure variability may confer additional benefits on target-organ protection. Effective target-organ protection could best be afforded by antihypertensive agents that provide efficient 24-h blood pressure control and also stabilize blood pressure variability. Mathematical indices, such as the trough:peak ratio and the smoothness index, provide useful measures of the homogeneity of the antihypertensive effect over 24 h; optimum control is provided by drugs with a trough:peak ratio close to 1 and a smoothness index > 1, as is observed with long-acting drugs such as telmisartan or amlodipine. Recently, a direct relationship was demonstrated between homogeneous blood pressure control and treatment-induced regression of left ventricular hypertrophy, emphasizing the importance of smooth 24-h blood pressure control. In conclusion, the goals of antihypertensive treatment should consider the reduction of both 24-h mean blood pressure and its variability. Long-lasting drugs or drug combinations are preferable to ensure a homogeneous and smooth 24-h blood pressure profile.

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Lowering blood pressure for cardiovascular risk reduction.

McInnes GT.

Division of Cardiovascular and Medical Sciences, Gardiner Institute, Western Infirmary, University of Glasgow, Glasgow, UK.

The association between blood pressure and cardiovascular risk is continuous, with no known lower threshold; epidemiologically, the lower the blood pressure, the better. In reality, the relationship must be J- or U-shaped, as a blood pressure of zero is associated with 100% mortality. However, the level of blood pressure control below which risk increases is well below that achieved in clinical practice, and reducing blood pressure is a cornerstone of strategies to reduce cardiovascular risk. Even relatively small reductions in blood pressure (systolic blood pressure 10-12 mmHg, diastolic blood pressure 5-6 mmHg) substantially reduce cardiovascular risk. Optimal cardiovascular protection is achievable through early and aggressive blood pressure control, but precisely which agents confer the greatest benefits for cardiovascular protection remains widely debated. Angiotensin II receptor blockers (ARBs) appear to be unique in providing additional protection beyond blood pressure control, whereas similar claims for other agents do not withstand close scrutiny. Nearly all patients with hypertension require several antihypertensive treatments to reach their target blood pressure, and it is important to choose treatments that are well tolerated and have complementary modes of action. For this reason, ARBs such as telmisartan emerge as logical choices for combination therapy, particularly when combined with a diuretic, as they fulfil all the essential requirements for combination therapy and are effective in a wide range of different types of patient. Regrettably, a rigorous approach to blood pressure control using multiple agents is still rare in general practice, partly because of a lack of understanding and partly because of 'professional non-compliance'. Prescribing habits must change, and soon, if we are to avoid an upsurge in cardiovascular complications.

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Relevance of blood pressure variation in the circadian onset of cardiovascular events.

Giles T.

Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA.

Ambulatory blood pressure monitoring enables the recording of the circadian rhythm of blood pressure under everyday circumstances, with the majority of individuals displaying diurnal variations in both systolic and diastolic blood pressures. During sleep, blood pressure in most people is between 10% and 20% lower than the mean daytime value. On arousal and the start of day-to-day activities, there is a surge in blood pressure that may last for between 4 and 6 h. Extensive evidence shows that ambulatory blood pressure is superior to office values in predicting cardiovascular risk. Cardiovascular events, such as myocardial infarction, ischaemia and stroke are more frequent in the morning hours, soon after waking, than at other times of day. Circadian variations in biochemical and physiological parameters help to explain the link between acute cardiovascular events and the early morning blood pressure surge. Recent observations in elderly Japanese individuals demonstrate that greater early morning blood pressure surges are related to an increased incidence of overt cerebrovascular disease; individuals with the greatest increases in blood pressure on awakening also had the greatest prevalence of silent ischaemic events and were more likely to experience multiple infarcts. Antihypertensive drugs that provide blood pressure control at the time of the early morning surge should provide greater protection against target-organ damage and enhance patient prognosis. Ambulatory blood pressure monitoring may be particularly helpful in assessing the circadian pharmacodynamics of such antihypertensive drugs. The technique has demonstrated, for example, a significantly greater reduction in blood pressure for the last 6 h of the 24-h dosing interval with telmisartan compared with valsartan.

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Endothelial Damage and Hemostatic Markers in Patients with Uncomplicated Mild-to-Moderate Hypertension and Relationship with Risk Factors.

Arikan E, Sen S.

Department of Endocrinology, Trakya University, Medical Faculty Edirne, Turkey. earikan trakya.edu.tr.

SUMMARY: Endothelial damage, high fibrinogen levels, and platelet activity are the important accelerating factors for the development of hypertension (HT). von Willebrand factor (vWF; endothelial damage marker), fibrinogen levels, and platelet aggregability were compared between patients with uncomplicated, mild-to-moderate hypertension and healthy subjects. The relationship between traditional cardiovascular risk factors and endothelial damage and prothrombotic state was evaluated. One hundred sixty-nine (54 males, 115 females) patients with untreated and uncomplicated mild-to-moderate HT, and age, gender, and body mass index-matched 124 (58 males, 83 females) healthy subjects were enrolled in this study. Plasma vWF, fibrinogen levels, adenosine diphosphate-induced platelet aggregability, insulin, glucose, serum lipids, and uric acid were measured. Patients with HT had significantly increased fibrinogen, vWF, platelet number and aggregability induced by adenosine diphosphate, triglycerides, total/HDL-C, glucose, uric acid levels, and insulin resistance than control group. vWF and hemostatic markers were comparable between smoker and nonsmoker subjects. Platelet aggregability was positively related to systolic and diastolic blood pressure, and vWF. Fibrinogen was positively associated with body mass index (BMI), systolic and diastolic blood pressure, total cholesterol (TC), uric acid, vWF, and insulin resistance. vWF was significantly related to age, systolic blood pressure, TC, LDL-C, and total/HDL-C. Systolic blood pressure was independently related to vWF. vWF and diastolic blood pressure were significant predictors for adenosine diphosphate-induced platelet aggregability. Systolic blood pressure and vWF were independent predictors for fibrinogen levels. Uncomplicated mild-to-moderate HT had endothelial damage and is associated with a prothrombotic state. Traditional cardiovascular risk factors such as age, BMI, dyslipidemia, and insulin resistance are important contributors to the development of endothelial damage and a prothrombotic state. Therefore, it is important to control these cardiovascular risk factors along with proper treatment of HT for preventing target organ damage in mild-to-moderate HT.

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Effect of flaxseed consumption on blood pressure, serum lipids, hemopoietic system and liver and kidney enzymes in healthy humans.

Stuglin C, Prasad K.

Departments of Physiology and Cardiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.

BACKGROUND: Effects of flaxseed on serum lipids have been studied in humans, but the results are variable. Flaxseed is ineffective in lowering blood pressure in rats. Its effect on blood pressure in humans is not known. It is also not known if long-term use of flaxseed in humans has deleterious effects on the hemopoietic system, serum glucose, and renal and kidney function. We investigated the effect of short-term use of flaxseed in humans on arterial pressure and serum lipids (triglycerides, total cholesterol; high-, low-, and very-low-density-lipoprotein cholesterol [HDL-C, LDL-C, VLDL-C], hemopoietic system (red blood cells, neutrophils, hemoglobin) and the various biochemical parameters, such as serum protein, albumin, total bilirubin, aspartate aminotransferase, alkaline phosphatase, creatinine, urea, related to hepatic and renal function, and serum glucose. METHODS: Fifteen healthy men, aged 22 to 47 years, consumed three muffins daily containing 32.7 g of total flaxseed for 4 weeks, in addition to their normal daily diet. Blood pressure and blood samples for various biochemical measurements were collected before and after 4 weeks of flaxseed diet. RESULTS: Blood pressures, heart rate, hemoglobin, and counts of red blood cells, white blood cells, and neutrophils remained unaltered after flaxseed diet. Serum total cholesterol, HDL-C, LDL-C, and VLDL-C remained unchanged, but serum triglycerides levels were elevated. Serum total bilirubin, aspartate aminotransferase, alkaline phosphatase, protein, albumin, glucose, and urea remained unaltered, but serum levels of creatinine decreased. CONCLUSION: These results suggest that 4 weeks use of flaxseed does not have deleterious effects on the hemopoietic system or renal and hepatic function and does not lower blood pressure and serum lipids. However, the level of serum triglyceride level was elevated.

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Acute effects of automated continuous positive airway pressure on blood pressure in patients with sleep apnea and hypertension.

Dursunoglu N, Dursunoglu D, Cuhadaroglu C, Kilicaslan Z.

Department of Chest Disease, Pamukkale University Medical Faculty, Denizli, Turkey. naydemir yahoo.com

BACKGROUND: The obstructive sleep apnea-hypopnea syndrome (OSAHS) is characterized by repetitive upper airway obstructions during sleep, and it might cause cardiovascular complications such as myocardial infarction, arrhythmias, and systemic and pulmonary hypertension. Objectives: We investigated the acute effects of automatic continuous positive airway pressure (automated CPAP) on blood pressure in patients with OSAHS and hypertension. METHODS: Polysomnography was used and ambulatory blood pressure measurements were done in 12 patients with OSAHS. Blood pressure and heart rate were measured at night (10 p.m. to 6 a.m.) and during the day (6 a.m. to 10 p.m.). During these periods systolic, diastolic and mean blood pressure and heart rate of the patients on the diagnostic day were compared with those on the treatment day. RESULTS: Patients had moderate or severe OSAHS; their mean age was 52.8+/-4.2 years. Systolic, diastolic and mean blood pressure and heart rate between the diagnostic and treatment day were not significantly different. Standard deviations of all these parameters during the night of the treatment day (9.1+/-4.5, 7.5+/-3.3, 8.0+/-3.0 mm Hg, and 4.8+/-1.5 beats/min, respectively) were significantly lower than during the night of the diagnostic day (12.6+/-4.9 mm Hg, p=0.023, 10.8+/-3.5 mm Hg, p=0.004, 11.6+/-4.4 mm Hg, p=0.006 and 6.9+/-1.6 beats/min, p=0.003, respectively). We did not find similar results during daytime periods. CONCLUSIONS: Automated CPAP therapy in patients with sleep apnea and hypertension did not decrease systolic and diastolic blood pressures and heart rates acutely. However, it might reduce the variability of these parameters during sleep in patients, but not during the day. It might be suggested that automated CPAP reduces cardiovascular morbidity of OSAHS via stabilizing heart rate and blood pressure during sleep. Copyright (c) 2005 S. Karger AG, Basel.

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