What Is Blood Pressure?

Blood pressure is the force of blood against the walls of arteries. Blood pressure is recorded as two numbers—the systolic pressure (as the heart beats) over the diastolic pressure (as the heart relaxes between beats). The measurement is written one above or before the other, with the systolic number on top and the diastolic number on the bottom. For example, a blood pressure measurement of 120/80 mmHg (millimeters of mercury) is expressed verbally as "120 over 80."  Normal blood pressure is less than 120 mmHg systolic and less than 80 mmHg diastolic.

Blood Pressure Level (mmHg)

(Ages 18 Years and Older)

Normal Systolic < 120
Normal Diastolic < 80

High Systolic 140–159
High Diastolic 90–99

Stage 2 Hypertension Systolic>160
Stage 2 Hypertension Diastolic >100

When systolic and diastolic blood pressures fall into different categories, the higher category should be used to classify blood pressure level. For example, 160/80 mmHg would be Stage 2-Hypertension (high blood pressure).

High blood pressure increases your chance (or risk) for getting heart disease and/or kidney disease, and for having a stroke. It is especially dangerous because it often has no warning signs or symptoms. Regardless of race, age, or gender, anyone can develop high blood pressure. It is estimated that one in every four American adults has high blood pressure. Once high blood pressure develops, it usually lasts a lifetime. You can prevent and control high blood pressure by taking action.

What Are High Blood Pressure and Pre-hypertension?

Blood pressure is the force of blood against the walls of arteries. Blood pressure rises and falls during the day. When blood pressure stays elevated over time, it is called high blood pressure.  The medical term for high blood pressure is hypertension. High blood pressure is dangerous because it makes the heart work too hard and contributes to arteriosclerosis (hardening of the arteries). It increases the risk of heart disease and stroke, which are the first- and third-leading causes of death among Americans. High blood pressure also can result in other conditions, such as congestive heart failure, kidney disease, and blindness.

 A blood pressure level of 140/90 mmHg or higher is considered high. About two-thirds of people over age 65 have high blood pressure. If your blood pressure is between 120/80 mmHg and 139/89 mmHg, then you have pre-hypertension. This means that you don't have high blood pressure now but are likely to develop it in the future. You can take steps to prevent high blood pressure by adopting a healthy lifestyle.

Those who do not have high blood pressure at age 55 face a 90 percent chance of developing it during their lifetimes. So high blood pressure is a condition that most people have at some point in their lives.  Both numbers in a blood pressure test are important, but for people who are 50 or older, systolic pressure gives the most accurate diagnosis of high blood pressure. Systolic pressure is the top number in a blood pressure reading. It is high if it is 140 mmHg or above.

What is systolic blood pressure?

Systolic pressure is the force of blood in the arteries as the heart beats. It is shown as the top number in a blood pressure reading. High blood pressure is 140 and higher for systolic pressure. Diastolic pressure does not need to be high for you to have high blood pressure. When that happens, the condition is called "isolated systolic hypertension," or ISH.

Is isolated systolic high blood pressure common?

Yes. It is the most common form of high blood pressure for older Americans. For most Americans, systolic blood pressure increases with age, while diastolic increases until about age 55 and then declines. About 65 percent of hypertensives over age 60 have ISH. You may have ISH and feel fine. As with other types of high blood pressure, ISH often causes no symptoms. To find out if you have ISH — or any type of high blood pressure — see your doctor and have a blood pressure test. The test is quick and painless.

Is isolated systolic high blood pressure dangerous?

Any form of high blood pressure is dangerous if not properly treated. Both numbers in a blood pressure test are important, but, for some, the systolic is especially meaningful. That's because, for those persons middle aged and older, systolic pressure gives a better diagnosis of high blood pressure.  If left uncontrolled, high systolic pressure can lead to stroke, heart attack, congestive heart failure, kidney damage, blindness, or other conditions.  While it cannot be cured once it has developed, ISH can be controlled. Clinical studies have proven that treating a high systolic pressure saves lives, greatly reduces illness, and improves the quality of life. Yet, most Americans do not have their high systolic pressure under control.

Does it require special treatment?

Treatment options for ISH are the same as for other types of high blood pressure, in which both systolic and diastolic pressures are high. ISH is treated with lifestyle changes and/or medications. The key for any high blood pressure treatment is to bring the condition under proper control. Blood pressure should be controlled to less than 140/90 mmHg. If yours is not, then ask your doctor why. You may just need a lifestyle or drug change, such as reducing salt in your diet or adding a second medication. 

What is diastolic blood pressure?

Diastolic pressure is the force of blood in the arteries as the heart relaxes between beats. It's shown as the bottom number in a blood pressure reading.  The diastolic blood pressure has been and remains, especially for younger people, an important hypertension number. The higher the diastolic blood pressure the greater the risk for heart attacks, strokes and kidney failure. As people become older, the diastolic pressure will begin to decrease and the systolic blood pressure begins to rise and becomes more important. A rise in systolic blood pressure will also increase the chance for heart attacks, strokes, and kidney failure. Your physician will use both the systolic and the diastolic blood pressure to determine your blood pressure category and appropriate prevention and treatment activities.

Why Is High Blood Pressure Important?

High blood pressure is dangerous because it makes the heart work too hard. It also makes the walls of the arteries hard. High blood pressure increases the risk for heart disease and stroke, the first- and third-leading causes of death for Americans. High blood pressure can also cause other problems, such as heart failure, kidney disease, and blindness.

Risk Factors for Heart Disease and Stroke

Risk factors are behaviors or conditions that can increase your chances of developing a disease. For instance, high blood pressure is a risk factor for heart disease and stroke.  There are other risk factors for heart disease and stroke. Most can be modified, though some cannot. The more risk factors you have, the greater your chances of developing disease. So it is important to take steps to prevent or control these risk factors.

Heart disease and stroke risk factors that can be controlled are:
- High blood pressure (hypertension)
- Abnormal cholesterol
- Tobacco use
- Diabetes
- Overweight
- Physical inactivity


Risk factors beyond your control are:
- Age (55 years and older for men and 65 years or older for women)
- Family history of early heart disease (having a mother or sister who has been diagnosed with heart disease before age 65, or a father or brother diagnosed before age 55) or family history of stroke

Effect of High Blood Pressure on Your Body

Stroke
High blood pressure is the most important risk factor for stroke. Very high pressure can cause a break in a weakened blood vessel, which then bleeds in the brain. This can cause a stroke. If a blood clot blocks one of the narrowed arteries, it can also cause a stroke.

Impaired Vision
High blood pressure can eventually cause blood vessels in the eye to burst or bleed. Vision may become blurred or otherwise impaired and can result in blindness.

Arteries
As people get older, arteries throughout the body "harden," especially those in the heart, brain, and kidneys. High blood pressure is associated with these "stiffer" arteries. This, in turn, causes the heart and kidneys to work harder.

Kidney Damage
The kidneys act as filters to rid the body of wastes. Over time, high blood pressure can narrow and thicken the blood vessels of the kidneys. The kidneys filter less fluid, and waste builds up in the blood. The kidneys may fail altogether. When this happens, medical treatment (dialysis) or a kidney transplant may be needed.

Heart Attack
High blood pressure is a major risk factor for heart attack. The arteries bring oxygen-carrying blood to the heart muscle. If the heart cannot get enough oxygen, chest pain, also known as "angina," can occur. If the flow of blood is blocked, a heart attack results.

Congestive Heart Failure
High blood pressure is the number one risk factor for congestive heart failure (CHF). CHF is a serious condition in which the heart is unable to pump enough blood to supply the body's needs.

What Causes High Blood Pressure?

The causes of high blood pressure vary. Causes may include narrowing of the arteries, a greater than normal volume of blood, or the heart beating faster or more forcefully than it should. Any of these conditions will cause increased pressure against the artery walls. High blood pressure might also be caused by another medical problem. Most of the time, the cause is not known. Although high blood pressure usually cannot be cured, in most cases it can be prevented and controlled.

Who Can Develop High Blood Pressure?

High blood pressure is common. About 65 million American adults — nearly 1 in 3 — have high blood pressure. It is very common in African Americans, who may get it earlier in life and more often than whites. Many Americans tend to develop high blood pressure as they get older, but this is not a part of healthy aging. Middle-aged Americans face a 90% chance of developing high blood pressure during their lives. Others at risk for developing high blood pressure are the overweight, those with a family history of high blood pressure, and those with pre-hypertension (120–139/80–89 mmHg). 

African Americans

High blood pressure occurs more often among African Americans than whites. It begins at an earlier age and is usually more severe. Further, African Americans have a higher death rate from stroke and kidney disease than whites. The good news is, treatment can control high blood pressure. In addition, lifestyle changes can prevent and control high blood pressure. These include losing weight if overweight (losing 10 lbs can help), increasing physical activity (walking 30 minutes per day can help), following a healthy eating plan, that emphasizes fruits, vegetables, and low-fat dairy foods, choosing and preparing foods with less salt and sodium, and if you drink alcoholic beverages, drinking in moderation. If lifestyle changes alone are not effective in keeping your blood pressure controlled, there are many blood pressure medications to help you.