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Hypertension  Blood pressure, the force of blood against the walls of arteries, rises and falls during the day. In hypertension, blood pressure stays above normal level over time. Hypertension often has no symptoms. If left untreated, it may cause stroke, heart attack, kidney problems, or blindness. Maintaining a healthy weight, proper diet, and exercise may help prevent hypertension. Treatment may include lifestyle changes and medications.
Hypertension: How high is too high?
Hypertension (hy-per-ten-shun) is the medical name for high blood pressure. Having blood pressure that's too high doesn't mean that you are "tense" or "stressed" or "nervous." Although being tense can raise blood pressure, a person who is very calm and relaxed can still have hypertension. Of the 50 million or more people with high blood pressure (hypertension) living in this country today, more than 35 percent -- 17.5 million -- don't know they have the disease. This is unfortunate, because hypertension can be easily identified, treated and controlled so that patients can lead normal, healthy lives. Do you have high blood pressure? A visit to your health care provider will answer the question.
Hyper-what?
In hypertension, your blood exerts increased pressure as it moves through your body. Your blood flows through miles of tubes, called arteries, like garden hoses running through your body. Blood pressure is the force with which the blood presses on the walls of these hoses. If you block a garden hose with your finger, the pressure in the hose rises because the water has nowhere to flow. This increased pressure strains the hose. Although, in hypertension, there are no "blockages" causing blood to back up, the elevated blood pressure puts a strain on your arteries.
Two factors control the pressure of blood in the arteries. The first is the amount of blood that the heart pumps into the arteries, and the second is the amount of resistance in the arteries and arterioles (smaller hoses). In people without hypertension, these two factors work together to maintain the blood pressure in a "normal" range. In people with hypertension, the regulation of this finely balanced system is disturbed and the blood pressure is consistently high. This damages both the heart and the arteries of the body, leading to the problems associated with high blood pressure: stroke, heart attacks and congestive heart failure.
Causes of High Blood Pressure
Essential or Primary Hypertension
Hypertension is referred to as essential, or primary, when the physician is unable to identify a specific cause. This is by far the most common type of high blood pressure, occurring in up to 95 percent of patients. Genetic factors appear to play a major role in essential hypertension. Several genetic factors, however are probably involved that regulate important physiologic processes and interact with environmental influences to produce essential high blood pressure. Experts appear to have located the chromosomes (13 and 18) that house the genes responsible for blood pressure regulation, although pinning down the range of specific genes involved in hypertension is more difficult.
Abnormalities in the Angiotensin-Renin-Aldosterone System
Genes under intense study are those that regulate a group of hormones known collectively as the angiotensin-renin-aldosterone system. This system influences all aspects of blood pressure control, including blood vessel contraction, sodium and water balance, and cell development in the heart. Experts believed that it evolved millions of years ago to protect early humans by retaining salt and water and narrowing blood vessels to ensure adequate blood flow and repair injured tissue. Over time, however, this system has become obsolete and instead of protecting people it wreaks havoc on modern humans. Of particular importance in these harmful responses are the hormone aldosterone and a peptide called angiotensin II.
Inherited Abnormalities in the Sympathetic Nervous System: Studies suggest that some people with essential hypertension may inherit abnormalities of the sympathetic nervous system, which is the part of the autonomic nervous system that controls heart rate, blood pressure, and the diameter of the blood vessels.
Insulin, Obesity, and Diabetes Type 2: Hypertension is the health problem most commonly associated with obesity, which in turn is strongly associated with type 2 diabetes. People with this form of diabetes generally have normal or high levels of insulin, a critical hormone in the metabolism of sugar. However, they are unable to use the insulin, a condition called insulin resistance.
Some research indicates that insulin resistance stimulates parts of the sympathetic nervous system and may cause sodium retention, a contributor to high blood pressure. Not all people with insulin resistance have hypertension, however, and not all those with high blood pressure have this problem, so any causal relationship is uncertain. Some research indicates that obesity is the only common element between insulin, diabetes type 2, and high blood pressure.
Obesity has a number of possible effects that could lead to hypertension. It may blunt certain actions of insulin that open blood vessels, cause structural changes in the kidney and abnormal handling of sodium, and is associated with alterations in the systems that regulate blood flow.
Low Levels of Nitric Oxide: Nitric oxide affects the smooth muscles cells that line blood vessels; it helps keep them relaxed, flexible, and may also help prevent blood clotting. Low levels of nitric oxide have been observed in people with high blood pressure (particularly in African Americans) and may be an important factor in essential hypertension.
Low Birth Weight: Low birth weight has been associated with high blood pressure in both childhood and adulthood. Whether this relationship is due to malnutrition in the mother or abnormalities in the placenta is not clear.
Secondary Hypertension
Secondary hypertension has recognizable causes, which are usually treatable or reversible.
Medical Conditions: Kidney disease is the most common cause of secondary hypertension, particularly in older people. Sleep apnea, a disorder in which breathing halts briefly but repeatedly during sleep, is associated with hypertension and increased sympathetic nerve activity. Patients with this disorder also have a poorer response to anti-hypertensive medications. Treatment with a device known as nasal continuous positive airway pressure may help lower blood pressure in some of these patients. Other medical conditions that contribute to temporary hypertension are pregnancy, cirrhosis, and Cushing's disease.
Medications: Certain prescription and over-the-counter drugs can cause temporary high blood pressure. Some prescription medications include cortisone, prednisone, estrogen, and indomethacin. Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) may injure the kidney and is an important cause of secondary hypertension in the elderly population. Such drugs include aspirin, ibuprofen (Advil, Motrin, Rufen), naproxen (Anaprox, Naprosyn, Aleve), and many others. Of these drugs, aspirin appears to have the least detrimental effect on blood pressure. Cold medicines containing pseudoephedrine have also been found to increase blood pressure in hypertensive people, although they appear to pose no danger for those with normal blood pressure. High blood pressure is known to be an uncommon side effect in a few women taking oral contraceptives (the Pill). Stopping the Pill nearly always reduces blood pressure, although a recent study suggests that oral contraceptives may produce a small but significant increase in diastolic pressure that persists in some older women who have been off the Pill for years.
Alcohol, Caffeine, Smoking, and Drugs: An estimated 10 percent of hypertension cases are caused by alcohol abuse, three alcoholic drinks a day or more, with heavier drinkers having higher pressure. In one study, binge-drinkers had even higher blood pressure than people who drank regularly. Although moderate drinking (one or two drinks a day) appears to have benefits for the heart and may even protect against some types of stroke, it is critical for heavy drinkers to abstain from alcohol.
Caffeine causes a temporary increase in blood pressure, which has been thought to be harmless in people with normal blood pressure. Studies are suggesting, however, that regular, heavy coffee drinking (an average of 5 cups per day) can boost blood pressure, and in one study, this was sufficient to increase the risk for heart disease in healthy men. The study was small, but there is growing evidence that a high intake of coffee may be harmful in people with hypertension and may even increase their risk for stroke. Drinking coffee also increases excretion of calcium, which also may affect blood pressure. (Anyone who drinks coffee should maintain an adequate calcium intake.)
The potential risk of caffeine, however, pale next to the dangers of smoking. One study reported that smokers have blood pressures up to 10 points higher than nonsmokers. Although cigar smoking does not appear to cause coronary artery disease, it can double the risk of death from cardiomyopathy and hypertension. Cocaine is known to cause acute episodes of hypertension.
Other Causes of Secondary High Blood Pressure
Temporary high blood pressure can result from stress, exercise, and long-term consumption of large amounts of licorice. Exposure to even low lead levels also appears to cause hypertension in adults. More studies are needed to clarify this relationship.
A 1999 study reported an association between exposure to mercury in the womb followed by higher blood pressure during childhood in a population living in the Faroe Islands. (The diet of such inhabitants includes whale meat, which increases the risk for mercury exposure.) High blood pressure associated with mercury exposure may persist long after the mercury has been removed. The findings of this study may be of concern for people who have diets that are high in fish protein. One small study showed that mobile phone use triggers a temporary rise in blood pressure, which may be harmful in people with existing hypertension.
Choosing Appropriate Treatments For High Blood Pressure
Aggressive drug treatment of long-term high blood pressure can significantly reduce the incidence of mental decline and death from heart disease and other serious physical effects of hypertension. In people with diabetes, controlling both blood pressure and blood glucose levels prevents serious complications of that disease. However, despite widespread access to medical care, there has been a reduction in awareness, treatment, and control of high blood pressure over the past decade. In a 1999 study of white Minnesotan adults, researchers reported that although over half of subjects had hypertension, 39 percent were unaware of their hypertensive status. Only 16.6 percent were treating and controlling their hypertension, and nearly 28 percent were being treated but their blood pressure was not under control. These results were significantly worse than those of a 1986 study of the same population. According to the American Heart Association, only one in four of 50 million people with high blood pressure are adequately treated.
To help make basic treatment choices for people with high-normal or high blood pressure, The National Heart, Lung and Blood Institute has created categories (denoted as Groups A, B, and C) according to a patient's risk factors for heart disease. Such risk factors include the following: smoking, unhealthy cholesterol and lipid levels, diabetes, being over 60 years old, being a man or postmenopausal woman, and women under 65 and men under 55 with a family history of heart disease. Applying these categories to the severity of hypertension helps determine whether lifestyle changes alone or medications are needed. (Regardless of their risk category, everyone with evidence of abnormal blood pressure should adapt a healthy diet and exercise program.) One study analyzed normal to severely hypertensive patients by risk group category and reported that only 2.4 percent (all women) were in risk group A, 59.3 percent were in group B, and 38.2 percent were in group C. In addition slightly over 60 percent were on or needed medications, according to the criteria.
Guidelines for Drug Therapy
General Recommendations for Specific Antihypertensives: Dozens of antihypertensive drugs are available. They usually fall into the following categories: (1) diuretics, which cause the body to excrete water and salt, (2) ACE inhibitors, which reduce the production of angiotensin, a chemical that causes arteries to constrict, (3) beta-blockers, which block the effects of adrenaline, thus easing the heart's pumping action and widening blood vessels, (4) vasodilators, which expand blood vessels, and (5) calcium-channel blockers, which help decrease the contractions of the heart and widen blood vessels. A single-drug regimen can often control mild to moderate hypertension. More severe hypertension often requires a combination of two or more drugs. Prolonged-release drugs are being developed so that they are most effective during early morning periods, when patients are at highest risk for heart attack or stroke.
As first-line treatment, experts generally recommend beta-blockers, diuretics, or both. They are inexpensive, safe, and effective for most people with hypertension who have no complicating problems. Individuals, however, may have special requirements that call for specific drugs.
Of some concern are studies indicating that beta-blockers used alone may not improve survival rates or reduce the risk for heart attack in hypertensive patients. They also increase the risk for diabetes. One analysis of many studies reported that diuretics were better than beta-blockers on all important points, including reducing heart attacks, strokes, and mortality rates.
In fact, studies that have reported benefits were generally reporting on combinations of diuretics and beta-blockers. One study even suggested that the combination is less effective than diuretics alone in some people. In any case, diuretics continue to be the best choice for most older adults and for many African Americans, who are more likely to be salt-sensitive and so respond well to these drugs.
Drug combinations containing low-dose diuretics along with other antihypertensives may prove to be particularly useful for elderly patients. Isolated high systolic pressure is usually treated with a diuretic; a long-acting calcium channel blocker may be an alternative.
For diabetics and perhaps for other patients with high-risk factors for heart problems, the best drugs are angiotensin-converting enzyme (ACE) inhibitors. This drug class has been shown to delay the onset and progression of kidney disease by 30 percent to 60 percent and to limit progression of other complications. People with heart failure should be given ACE inhibitors and diuretics; specific drugs in these classes may be particularly beneficial for these patients because they reduce left ventricle hypertrophy.
Side Effects and Compliance: All drugs used for hypertension have side effects, some very distressing, and ongoing compliance is difficult. Some physicians have been concerned about the long-term effects of anti-hypertensive drugs on mental processes. One study reported change in brain tissue on scans of people who took calcium-channel blockers or loop diuretic; those who took beta-blockers had no such changes. This is an isolated study, and more research is needed to confirm it. A 1999 study reported, in fact, that diuretics protect against dementia. On an encouraging note, one major study found that people taking blood pressure drugs did not experience any greater decline in the general quality of life or daily functioning over five years than did people who were not on blood pressure medication. In all cases, healthy lifestyle changes must accompany any drug treatment. It is very important, in any case, to rigorously maintain a drug regimen.
Withdrawal From Antihypertensive Medications: Patients whose blood pressure has been well-controlled and who are able to maintain a healthy life style may choose to withdraw from hypertensive medications. They should do so in a step-down manner (gradual reduction) and be monitored regularly. Stopping too quickly can have adverse effects, including serious effects on the heart in some cases. Research is ongoing to determine which patients are more likely to sustain control of their blood pressure after withdraw. Long-term success rates (more than a year after withdrawal) in patients whose blood pressure had been well controlled range from 15 percent to more than 80 percent. The highest success rates are more likely in those who lose weight and reduce sodium intake and who are able to control their blood pressure within five years of an initial diagnosis and treatment with a single agent. Of concern was a 1998 study reporting that patients, particularly smokers and younger adults, who discontinue antihypertensive therapy are at a significantly increased risk for stroke.
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