Blood pressure is the amount of force your blood exerts against the walls of your arteries. Normal blood pressure effectively and harmlessly pushes the blood from your heart to your body's organs and muscles so they can receive the oxygen and nutrients they need.

Blood pressure is variable--it rises and falls during the day. When blood pressure stays elevated over time, however, it is called high blood pressure or hypertension.

According to the most recent estimates, up to 65 million Americans have hypertension, or high blood pressure, and nearly half are women, according to the American Heart Association. High blood pressure killed nearly 50,000 Americans in 2002, and was listed as a primary or contributing factor in 261,000 deaths.

Hypertension can occur in both children and adults, but it is more common in adults, particularly African Americans, overweight people, people who drink heavily (defined as more than two drinks a day for men and one drink a day for women), elderly and middle-aged people and women who are taking oral contraceptives. Additionally, people with diabetes, kidney disease or gout have a higher risk of hypertension. Overall, one in three American adults has hypertension.

More men than women have hypertension, until women reach menopause, when their risk becomes greater than men's. About half of the 65 million Americans with high blood pressure are women About 20 percent of white women and 30 to 40 percent of African-American women have high blood pressure, and the prevalence rises to 80 percent in women over age 70.

 

Blood pressure is typically expressed as two numbers, one over the other, and is measured in millimeters of mercury (noted as mmHg). The first number is the systolic systolic blood pressure, the pressure used when the heart beats. The second number, or diastolic blood pressure, is the pressure that exists in the arteries between heartbeats.

Depending on your activities, your blood pressure may increase or decrease throughout the day. If you are not acutely ill, are over 18 years of age, and are not taking antihypertensive drugs, a blood pressure reading of less than 120 mmHg systolic and less than 80 mmHg diastolic (120/80) is considered normal.

If your blood pressure is between 120/80 mmHg and 139/89 mmHg, you have prehypertension. This means that you don't have high blood pressure now but are more likely to develop it in the future, and you have increased risk factors for cardiovascular disease and other conditions related to hypertension.

A blood pressure level of 140/90 mmHg or higher is considered high.

You may also have hypertension if either your systolic or diastolic is greater than or equal to 140 or 90 mmHg, respectively. That is, you can have isolated systolic or diastolic hypertension. Isolated systolic hypertension (ISH) This is the most common form of high blood pressure in older Americans. The National Heart, Lung and Blood Institute (NHLBI) estimates that 65 percent of people with hypertension over age 60 have ISH.

The cause of approximately 90 to 95 percent of all hypertension isn't known. This type of hypertension is called primary or essential high blood pressure. When the cause is known, it's called secondary hypertension. While there is no cure for hypertension, it is easily detected and is usually controllable.

Still, nearly one third of those who suffer from high blood pressure don't know they have it, and people can have high blood pressure for years without knowing they have it. That's why high blood pressure has been called "the silent killer."

Of those with hypertension, only 34 percent have the problem under control, defined as a level below 140/90 mm/Hg. Left untreated, hypertension can result in permanent damage to the small blood vessels of the body, which can damage vital organs and increase the risk of heart attack and stroke. It can also cause acute or chronic circulatory problems.

Even slightly elevated blood pressure levels can double your risk for coronary heart disease. In fact, recent studies show that in adults ages 40�?9, the risk of death from heart disease and stroke begins to rise at blood pressures as low as 115/75. This risk doubles for each increased increment of 20 mm/Hg in systolic blood pressure or 10 mm/Hg in diastolic blood pressure. Consistent high blood pressure also increases your risk for congestive heart failure, and can lead to other problems such as:

Atherosclerosis: Plaque collects on the walls of hypertension-damaged blood vessels, which can eventually lead to blockages that may result in a stroke or heart attack. Although this plaque builds up for many reasons as you age, high blood pressure hastens the process.

Eye damage: High pressure in blood vessels can cause tiny hemorrhages in the retina, the light-sensitive membrane in the back of your eye on which images are formed. If this happens, you may lose some of your vision.

Heart enlargement or failure: There are two types of heart failure. In the first, the walls of the heart are weak and thin as a result of being stretched by increasing amounts of pooling blood in the heart. In the second, commonly seen in people with hypertension, the heart muscle enlarges in response to the higher pressure and increased workload. It becomes so big it begins to close off the ventricular chamber, decreasing the amount of blood that can fill the heart. This is called diastolic dysfunction , because the heart muscle can't relax normally and allow blood to fill the chamber.

Kidney damage and failure: Hypertension causes arteries going to your kidneys to become constricted, making them less efficient at filtering waste from your body. About 25 percent of people who require kidney dialysis have kidney failure due to hypertension. This is especially true in African Americans. Early treatment of hypertension can help prevent kidney damage.

You should have your blood pressure checked whenever you see a health care professional. Because blood pressure can be variable, it should be checked on several different days before a high blood pressure diagnosis is made. One elevated blood pressure reading doesn't necessarily mean you have high blood pressure, but it does warrant repeated measurement and means you have to watch your blood pressure carefully.

Dietary and lifestyle changes may help you control high blood pressure. If you have mild hypertension, you may be able to lower your blood pressure by reducing the amount of sodium (salt) in your diet, reducing fat intake, eating a diet high in fruits, vegetables and low-fat dairy (the DASH diet), and reducing alcohol consumption. If you are overweight, losing weight may reduce your blood pressure. Increasing your physical activity, even if you don't lose weight, can also reduce blood pressure.

For some people, lifestyle changes aren't enough to lower blood pressure. Luckily, high blood pressure can be treated very successfully with long-term medication.

Commonly prescribed drugs include diuretics, beta-blockers, angiotension inhibitors (ACEIs), calcium angiotensin blockers (AGBs), calcium channel blockers (CCBs). Because there is no cure for most hypertension cases, treatment generally must be carried out for life to prevent blood pressure from rising again.

Many of these drugs are also available to treat isolated systolic hypertension (ISH) to reduce your risk of coronary heart disease and stroke.