High blood pressure (HBP) or hypertension means high pressure (tension) in the arteries. Arteries are vessels that carry blood from the pumping heart to all the tissues and organs of the body. High blood pressure does not mean excessive emotional tension, although emotional tension and stress can temporarily increase blood pressure. Normal blood pressure is below 120/80; blood pressure between 120/80 and 139/89 is called "pre-hypertension", and a blood pressure of 140/90 or above is considered high.
The top number, the systolic blood pressure, corresponds to the pressure in the arteries as the heart contracts and pumps blood forward into the arteries. The bottom number, the diastolic pressure, represents the pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure reflects the lowest pressure to which the arteries are exposed.
An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart (cardiac) disease, kidney (renal) disease, hardening of the arteries (atherosclerosis or arteriosclerosis), eye damage, and stroke (brain damage). These complications of hypertension are often referred to as end-organ damage because damage to these organs is the end result of chronic (long duration) high blood pressure. For that reason, the diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
It was previously thought that rises in diastolic blood pressure were a more important risk factor than systolic elevations, but it is now known that in people 50 years or older systolic hypertension represents a greater risk.
The American Heart Association estimates high blood pressure affects approximately one in three adults in the United States -- 73 million people. High blood pressure is also estimated to affect about two million American teens and children, and the Journal of the American Medical Associationreports that many are underdiagnosed. Hypertension is clearly a major public health problem.
The top number, the systolic blood pressure, corresponds to the pressure in the arteries as the heart contracts and pumps blood forward into the arteries. The bottom number, the diastolic pressure, represents the pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure reflects the lowest pressure to which the arteries are exposed.
An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart (cardiac) disease, kidney (renal) disease, hardening of the arteries (atherosclerosis or arteriosclerosis), eye damage, and stroke (brain damage). These complications of hypertension are often referred to as end-organ damage because damage to these organs is the end result of chronic (long duration) high blood pressure. For that reason, the diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
It was previously thought that rises in diastolic blood pressure were a more important risk factor than systolic elevations, but it is now known that in people 50 years or older systolic hypertension represents a greater risk.
The American Heart Association estimates high blood pressure affects approximately one in three adults in the United States -- 73 million people. High blood pressure is also estimated to affect about two million American teens and children, and the Journal of the American Medical Associationreports that many are underdiagnosed. Hypertension is clearly a major public health problem.
What causes it
Two forms of high blood pressure have been described -- essential (or primary) hypertension and secondary hypertension. Essential hypertension is a far more common condition and accounts for 95% of hypertension. The cause of essential hypertension is multifactorial, that is, there are several factors whose combined effects produce hypertension. In secondary hypertension, which accounts for 5% of hypertension, the high blood pressure is secondary to (caused by) a specific abnormality in one of the organs or systems of the body. (Secondary hypertension is discussed further in a separate section later.)Essential hypertension affects approximately 72 million Americans, yet its basic causes or underlying defects are not always known. Nevertheless, certain associations have been recognized in people with essential hypertension. For example, essential hypertension develops only in groups or societies that have a fairly high intake of salt, exceeding 5.8 grams daily. Salt intake may be a particularly important factor in relation to essential hypertension in several situations, and excess salt may be involved in the hypertension that is associated with advancing age, African American background, obesity, hereditary (genetic) susceptibility, and kidney failure (renal insufficiency). The Institute of Medicine of the National Academies recommends healthy 19 to 50-year-old adults consume only 3.8 grams of salt to replace the average amount lost daily through perspiration and to achieve a diet that provides sufficient amounts of other essential nutrients.
Genetic factors are thought to play a prominent role in the development of essential hypertension. However, the genes for hypertension have not yet been identified. (Genes are tiny portions of chromosomes that produce the proteins that determine the characteristics of individuals.) The current research in this area is focused on the genetic factors that affect the renin-angiotensin-aldosterone system. This system helps to regulate blood pressure by controlling salt balance and the tone (state of elasticity) of the arteries.
Approximately 30% of cases of essential hypertension are attributable to genetic factors. For example, in the United States, the incidence of high blood pressure is greater among African Americans than among Caucasians or Asians. Also, in individuals who have one or two parents with hypertension, high blood pressure is twice as common as in the general population. Rarely, certain unusual genetic disorders affecting the hormones of the adrenal glands may lead to hypertension. (These identified genetic disorders are considered secondary hypertension.)
The vast majority of patients with essential hypertension have in common a particular abnormality of the arteries: an increased resistance (stiffness or lack of elasticity) in the tiny arteries that are most distant from the heart (peripheral arteries or arterioles). The arterioles supply oxygen-containing blood and nutrients to all of the tissues of the body. The arterioles are connected by capillaries in the tissues to the veins (the venous system), which returns the blood to the heart and lungs. Just what makes the peripheral arteries become stiff is not known. Yet, this increased peripheral arteriolar stiffness is present in those individuals whose essential hypertension is associated with genetic factors, obesity, lack of exercise, overuse of salt, and aging. Inflammation also may play a role in hypertension since a predictor of the development of hypertension is the presence of an elevated C reactive protein level (a blood test marker of inflammation) in some individuals.
Treatment
Research has shown that following a healthy eating plan can both reduce the risk of developing high blood pressure and lower an already elevated blood pressure.
For an overall eating plan, consider the DASH eating plan. "DASH" stands for "Dietary Approaches to Stop Hypertension," a clinical study that tested the effects of nutrients in food on blood pressure. Study results indicated that elevated blood pressures were reduced by an eating plan that emphasizes fruits, vegetables, and lowfat dairy foods and is low in saturated fat, total fat, and cholesterol. The DASH eating plan includes whole grains, poultry, fish, and nuts and has reduced amounts of fats, red meats, sweets, and sugared beverages.
A second clinical study, called "DASH-Sodium," looked at the effect of a reduced dietary sodium intake on blood pressure as people followed either the DASH eating plan or a typical American diet. Results showed that reducing dietary sodium lowered blood pressure for both the DASH eating plan and the typical American diet. The biggest blood pressure-lowering benefits were for those eating the DASH eating plan at the lowest sodium level (1,500 milligrams per day).
The DASH-Sodium study shows the importance of lowering sodium intake whatever your diet. But for a true winning combination, follow the DASH eating plan and lower your intake of salt and sodium.
For an overall eating plan, consider the DASH eating plan. "DASH" stands for "Dietary Approaches to Stop Hypertension," a clinical study that tested the effects of nutrients in food on blood pressure. Study results indicated that elevated blood pressures were reduced by an eating plan that emphasizes fruits, vegetables, and lowfat dairy foods and is low in saturated fat, total fat, and cholesterol. The DASH eating plan includes whole grains, poultry, fish, and nuts and has reduced amounts of fats, red meats, sweets, and sugared beverages.
A second clinical study, called "DASH-Sodium," looked at the effect of a reduced dietary sodium intake on blood pressure as people followed either the DASH eating plan or a typical American diet. Results showed that reducing dietary sodium lowered blood pressure for both the DASH eating plan and the typical American diet. The biggest blood pressure-lowering benefits were for those eating the DASH eating plan at the lowest sodium level (1,500 milligrams per day).
The DASH-Sodium study shows the importance of lowering sodium intake whatever your diet. But for a true winning combination, follow the DASH eating plan and lower your intake of salt and sodium.
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