High Blood Pressure (Hypertension)

  • Basics

    Hypertension is the medical term for high blood pressure. As blood travels through your body, it presses against the walls of the blood vessels. If your vessels become narrowed, your heart has to pump harder to maintain circulation, thus exerting more pressure against the vessel walls. Eventually, this high pressure will increase your risk of developing heart disease and stroke. Your heart also has to work harder when pushing against a “high-pressure” system. This increased workload makes your heart larger and more inefficient. High blood pressure also can lead to congestive heart failure, kidney damage or kidney failure, dementia, and blindness.

    Hypertension is an extremely common health problem, affecting about one in four adults in the U.S. Unfortunately, hypertension often has no symptoms, and can only be diagnosed through regular blood pressure readings taken by a health care professional. Once detected, hypertension is usually controllable. If you are curious about your blood pressure, ask your caregiver to take a quick reading.

    Blood pressure readings are given with two numbers: one expressing the pressure generated when your heart is beating (systolic pressure), and the other measuring the pressure between beats (diastolic pressure) Figure 01. As your blood pressure increases, your systolic and diastolic blood pressure readings will both increase. However, your systolic blood pressure (the first number in the reading) may be more important in older people than the diastolic level or the combined reading. That is because in industrialized countries, systolic blood pressure increases steeply with age. Diastolic blood pressure, on the other hand, increases until about age 55, and then declines. Many Americans over the age of 60 with hypertension have increased systolic pressure (at or above 140) but normal diastolic pressure (under 90). This condition is known as isolated systolic hypertension (ISH). Since ISH is a significant risk factor for heart attack, heart failure, and stroke, experts recommend that your systolic blood pressure should be under 140.

    Click to enlarge: Systolic and diastolic pressure (animation and audio)

    Figure 01. Systolic and diastolic pressure (animation and audio)

    Controlling your blood pressure becomes more important as you get older. Many people think that as they get older, good blood pressure control becomes less important. In fact, the opposite is true; elderly people actually prevent more bad outcomes such as stroke and heart attacks than do younger patients by controlling their blood pressure.

    There are three stages of hypertension: mild, moderate, and severe. All of the stages require treatment Figure 02.

    Click to enlarge: Blood pressure categories

    Figure 02. Blood pressure categories

    A life-threatening form of hypertension, known as malignant or accelerated hypertension, is extremely rare. Malignant or accelerated hypertension affects less than 1% of hypertensive patients. Unlike the more common form of hypertension that usually develops over a number of years, this condition is marked by a rapid rise in blood pressure, with the diastolic pressure shooting to 130 or higher. Accelerated hypertension is a life-threatening condition, and must be treated immediately.

  • Causes

    About 90% to 95% of hypertension cases, called primary, or essential hypertension, have no known cause. Primary hypertension may be influenced by factors such as genetic makeup, weight, or salt intake. Research is underway to learn more about the role that genes play in hypertension, as well as to explore the association between hypertension and factors such as obesity, low birth weight, and low levels of nitric oxide. Nitric oxide is a molecule that affects the smooth muscle cells that line blood vessels. People with low levels of nitric oxide have been found to have high blood pressure; especially African-Americans with low levels of the molecule.

    Secondary hypertension is hypertension that is caused by an underlying medical condition. Secondary hypertension is the name given to high blood pressure that has a specific cause, such as a thyroid or a kidney problem. The most common cause of secondary hypertension is kidney disease. Secondary hypertension may also occur during pregnancy or in conjunction with sleep apnea, cirrhosis, Cushing's disease (a disorder of the adrenal gland), thyroid dysfunction, and various other medical conditions.

    Secondary hypertension is much less common than essential hypertension (~5%), and tends to develop more rapidly than primary or essential hypertension.

    A variety of prescription and over-the-counter medications can cause temporary high blood pressure or interfere with hypertension therapy. Drugs known to have this effect include cortisone, cyclosporine, prednisone, estrogen (including birth control pills), monoamine oxidase inhibitors, nasal decongestants, and amphetamines. Long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofin, and naproxen can also cause hypertension by damaging the kidneys.

    Alcohol, smoking, drugs, and caffeine can cause secondary hypertension. If you drink heavily, you have an increased risk of developing high blood pressure and associated health problems, such as strokes. One drink of alcohol per day may protect your heart, but more than that can cause damage an increase your risk of developing high blood pressure. Smoking is also a significant contributor to high blood pressure. Smokers may have blood pressure levels up to 10 points higher than nonsmokers. The caffeine in coffee, tea, and colas causes a slight, temporary increase in blood pressure; some studies have suggested that heavy coffee drinking (an average of four or five cups a day) can cause a more lasting and potentially harmful rise in blood pressure. Cocaine can cause acute episodes of hypertension.

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