Hypertension is arbitrarily defined as a level of blood pressure at which a person has an increased risk of developing a morbid cardiovascular event or will clearly benefit from medical therapy. Hypertension is defined clinically as an elevation in arterial blood pressure equal to or exceeding a systolic blood pressure of 140 mmHg and/or a diastolic blood pressure of 90 mmHg.
Hypertension is one of the most prevalent forms of cardiovascular disease affecting approximately 1 billion individuals worldwide( ).
Untreated hypertension leads to premature death, the most common cause being heart disease, followed by stroke and renal failure. Hypertension damages the endothelium (a thin layer that lines the inner surface of blood vessels), which predisposes the individual to atherosclerosis (disease in which deposits of cholesterol and other lipids are formed within arteries) and other vascular pathologies.
In the presence of hyperlipidemia (elevated lipid levels in the blood) and a damaged endothelium, atherosclerotic plaque develops, whereas in its absence, the intima (inner layer of blood vessels) thickens. Arteries throughout the body harden faster, especially those in the heart, brain and kidneys, which can cause a heart attack, stroke or kidney failure( ). High blood pressure also affects the brain. People with elevated blood pressure in middle age are more likely to suffer 25 years later from loss of cognitive abilities- memory, problem solving, concentration and judgement( ). This loss further translates into a diminished capacity to function independently in old age.
Hypertension and Weight Loss
The association between obesity and hypertension is well established. Being overweight results in a two-to sixfold increase in the risk of developing hypertension, with the risk climbing in a stepwise manner with increasing body weight. Risk estimates from the Framingham Heart Study suggest that approximately 75% and 65% of the cases of hypertension in men and women, respectively, are directly attributable to overweight and obesity( ).
A review of randomized controlled trials of over 6 months duration analyzing the effect of weight reduction in reducing BP found a decrease of 5.2/5.2 mmHg and 2.8/2.3 mmHg in hypertensive and normotensive participants, respectively( ). Weight reduction enhances the effects of antihypertensive medications and positively affects other cardiovascular risk factors, such as diabetes and dyslipidemia (elevated lipid levels in the blood).
Hypertension and Age
In the United States and most other Western societies, the large majority of residents experience a progressive age-related rise in blood pressure. As a result, the incidence and prevalence of hypertension rise steadily with each additional decade of life. Two million new hypertensives are added each year to the pool of patients in the United States, so that by old age, about two thirds of Americans have this disease.
The fact that the prevalence of hypertension increases so dramatically with age suggests that high blood pressure is an inevitable consequence of aging. This is not the case, however, and there are reports from several groups around the world demonstrating that blood pressure does not always increase with age. One such group are the Kung Bushmen of Northern Botswana. This is an isolated group who live as hunter-gatherers all year round. In contrast to the situation in developed countries, systolic and diastolic blood pressure remain low throughout life in male and female Kung Bushmen. Several factors may explain the low blood pressure values of the Kung Bushmen including a low salt intake, freedom from the stresses of civilization and high levels of physical activity which are characteristics of a hunter-gather lifestyle.
In societies where salt and alcohol intakes are high, potassium intake is low, and physical inactivity and obesity are the norm, incidence of hypertension is high( ).
Hypertension and Exercise
Exercise training has been recommended as one of the important lifestyle modifications for the prevention and management of hypertension( ). In general, sedentary and unfit normotensive individuals have a 20-50% increased risk of developing hypertension during follow up when compared with their more active and fit peers( ).
Recent meta-analysis( ) from over 54 randomized clinical trials, involving more than 2600 subjects indicate that aerobic exercise training will elicit average reductions of 3 to 4mmHg and 2 to 3mmHg for systolic and diastolic pressure, respectively. However, the reductions subsequent to aerobic training appear to be more pronounced in hypertensive subjects (i.e., -7.4 and -5.8mmHg for systolic and diastolic pressure)( ).With respect to training protocols, changes in blood pressure following aerobic training appear to be similar with training intensities between 40% and 70% of VO2max, for training frequencies 3 to 5 days per week, and for training durations of 30 to 60 minutes( ).
Reductions in blood pressure following aerobic exercise training appear to be independent of both baseline obesity status and weight loss during training( ).
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