High Blood Pressure

About High Blood Pressure

The following information is provided by the Centers for Disease Control. For more information, visit www.cdc.gov.

What is High Blood Pressure?

Blood pressure is the force of blood against the artery walls. It is often written or stated as two numbers. The first or top number represents the pressure when the heart contracts. This is called systolic pressure. The second or bottom number represents the pressure when the heart rests between beats. This is called diastolic pressure.

Blood pressure is traditionally measured with a device called a sphygmomanometer. It measures blood pressure in millimeters of mercury (mmHg). An inflatable cuff is wrapped around the arm and is inflated to squeeze the blood vessels in the arm. The health care provider uses a stethoscope to listen to the pulse as the pressure is released in order to determine the systolic and diastolic pressure. Some blood pressure testing devices are now electronic and provide digital readouts of the blood pressure measurement and pulse rate.

Blood pressure normally rises and falls throughout the day. When it consistently stays too high for too long, it is called hypertension. The Seventh Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure notes these levels for defining normal and high blood pressure in adults:

* High blood pressure or hypertension for adults is defined as a systolic blood pressure of 140 mmHg or higher or a diastolic blood pressure of 90 mmHg or higher.

* Normal blood pressure is a systolic blood pressure of less than 120 mmHg and a diastolic blood pressure of less than 80 mmHg.

* Prehypertension is defined as a systolic blood pressure of 120–139 mmHg or a diastolic blood pressure of 80–89 mmHg. Persons with prehypertension are at increased risk to progress to hypertension.

If the systolic and diastolic blood pressure levels are in different categories, blood pressure status is defined according to the higher category. For example, a person with a high systolic pressure but a normal diastolic pressure will be considered to have high blood pressure (sometimes referred to as systolic hypertension). A person with a high diastolic pressure but a normal systolic pressure will be considered to have high blood pressure also (sometimes referred to as diastolic hypertension).

High blood pressure for adults will usually be measured on at least two different doctor visits before a diagnosis of high blood pressure is made.

For children, high blood pressure is determined by comparing the child’s blood pressure with the distribution of blood pressure for children of similar sex, age and height. A child whose blood pressure is greater than or equal to 95% of children of similar sex, age, and height (at or above the 95th percentile) would be considered to have high blood pressure. Prehypertension in children is classified as a blood pressure of 120/80 mmHg or higher but below the 95th percentile. A diagnosis of high blood pressure should be based on blood pressure readings on at least three different visits. The correct–size blood pressure cuff must be used.

More importantly, high blood pressure can be prevented or controlled through lifestyle changes and with medications when needed.

Types of High Blood Pressure

Essential hypertension—in most cases, high blood pressure does not have a specific treatable cause. This form is called essential hypertension.

Secondary hypertension—in a few cases, the cause of hypertension is some other underlying condition. This is called secondary hypertension. This may be due to kidney disorders, congenital abnormalities, or other conditions. Blood pressure usually returns to normal when the problem is corrected.

Pregnancy–related hypertension—existing high blood pressure can predispose some women to develop problems when they become pregnant. This is called pre-existing chronic hypertension. Also, some women first develop hypertension when they are pregnant. There are several types of this pregnancy–induced hypertension, sometimes called gestational hypertension. Either type of high blood pressure can harm the mother's kidneys and other organs, and it can cause low birth weight and early delivery. Preeclampsia is a serious condition of pregnancy and is related to increased blood pressure and protein in the mother's urine (as a result of kidney problems). Preeclampsia affects the placenta, and it can affect the mother's kidney, liver, and brain. When preeclampsia progresses and seizures develop, the condition is known as eclampsia—the second leading cause of maternal death in the United States. Preeclampsia is also a leading cause of fetal complications, which include low birth weight, premature birth, and stillbirth. Most women who develop signs of preeclampsia are closely monitored to lessen or to avoid related problems. Treatment is focused on reducing water retention and lowering blood pressure to normal limits.

Treatment of High Blood Pressure

High blood pressure can be treated with both lifestyle modifications, usually as the first step, and, if needed, with medications. Lifestyle factors to treat high blood pressure include weight control, exercise, healthy diet, limiting alcohol use, and other lifestyle modifications. See our prevention page for more on these lifestyle factors.

There are several types of medications that are used to treat high blood pressure. Frequently, more than one type will be used. It is important to take these as prescribed. High blood pressure medicines fall into one of these types:

* Diuretics work in the kidney and flush excess water and sodium from the body. They are sometimes called "water pills."

* Beta–blockers reduce nerve impulses to the heart and blood vessels that make the heart beat slower and with less force.

* Angiotensin–converting enzyme (ACE) inhibitors cause the blood vessels to relax. ACE inhibitors prevent the formation of a hormone called angiotensin II, which normally causes the blood vessels to narrow.

* Angiotensin antagonists shield the blood vessels from angiotensin II. As a result, the vessels become wider.

* Calcium channel blockers prevent calcium from entering the muscle cells of the heart and blood vessels. This causes the blood vessels to relax.

* Alpha–blockers reduce nerve impulses to the blood vessels, which allows the blood to pass more easily.

* Alpha–beta–blockers work the same way as alpha-blockers but also slow the heartbeat, as beta–blockers do. As a result, less blood is pumped through the vessels.

* Nervous system inhibitors relax blood vessels by controlling nerve impulses. This causes the blood vessels to become wider.

* Vasodilators directly open the blood vessels by relaxing the muscle in the vessel walls.

Outcomes of High Blood Pressure

High blood pressure is often called the ‘silent killer’ because it usually has no noticeable warning signs or symptoms until other serious problems arise. Therefore, many people with high blood pressure do not know that they have it. High blood pressure is a major risk factor for heart disease, the leading cause of death in the United States. It can lead to hardened or stiffened arteries, which causes a decrease of blood flow to the heart muscle and other parts of the body. Reduced blood to the heart muscle can lead to angina (chest pain or damage to the heart muscle due to a lack of blood carrying oxygen to the heart muscle) or to a heart attack (caused by a chronic spasm or blockage of blood and oxygen to the heart).

High blood pressure is a major risk factor for heart failure, a serious condition where the heart cannot pump enough blood for the body’s needs. It is also the major risk factor for stroke, which is the third leading cause of death in the United States. A stroke may be caused by a rupture or blockage of an artery that supplies blood and oxygen to the brain.

In addition, high blood pressure can result in damage to the eyes, including blindness. The blood vessels in the eyes can rupture or burst from high blood pressure leading to impairment of sight.

High blood pressure can also result in kidney disease and kidney failure. The kidneys filter wastes from fluids in the body. High blood pressure can thicken and narrow the blood vessels of the kidneys, resulting in less fluid being filtered and wastes building up in the body. Also, diseases of the kidney can be a cause of high blood pressure.

There are several things that you can do to keep your blood pressure healthy. These actions should become part of your regular lifestyle. You should discuss with your health care provider the best ways for you to address these issues.

Maintain a Healthy Weight

Being overweight or obese can raise your blood pressure, and losing weight can help you lower your blood pressure. Healthy weight status in adults is usually assessed by using weight and height to compute a number called the "body mass index" (BMI). BMI is used because it relates to the amount of body fat for most people. An adult who has a BMI of 30 or higher is considered to be obese. Overweight is a BMI between 25 and 29.9. Normal weight is a BMI of 18 to 24.9. Proper diet and regular physical activity can help to maintain a healthy weight. Other measures of excess body fat may include waist measurements or waist and hip measurements. If you know your weight and height, you can compute your BMI at the CDC's Nutrition and Physical Activity Program Web site.

Be Active

Being physically inactive is related to high blood pressure, and physical activity can help to lower blood pressure. The Surgeon General recommends that adults should engage in moderate–level physical activities for at least 30 minutes on most days of the week. For more information, see the CDC's Nutrition and Physical Activity Program Web site.

Maintain a Healthy Diet

Along with healthy weight and regular physical activity, an overall healthy diet can help to maintain healthy blood pressure levels. This includes eating lots of fresh fruits and vegetables and lowering or cutting out salt or sodium and increasing potassium. High salt and sodium intake and a low potassium intake (due to not eating enough fruits and vegetables) can increase blood pressure. You need to watch the sodium that is already included in processed foods and to avoid adding sodium or salt in cooking or at the table. Low saturated fat and cholesterol are also part of an overall healthy diet. Recent studies such as the Dietary Approaches to Stop Hypertension (DASH) trial show that blood pressure can be significantly lowered through diet. For more information on diet and nutrition, see CDC's Nutrition and Physical Activity Program Web site.

Moderate Alcohol Use

Excessive alcohol consumption is related to increased blood pressure. People who drink alcohol should do so in moderation. Based on current dietary guidelines, moderate drinking for women is defined as an average of one drink or less per day. Moderate drinking for men is defined as an average of two drinks or less per day. More information on alcohol can be found at the CDC's Alcohol and Public Health Web site.

Prevent and Control Diabetes

People with diabetes have a higher risk of high blood pressure, but they can also work to reduce their risk. Recent studies suggest that all people can take steps to reduce their risk of diabetes. These include a healthy diet, weight loss and regular physical activity. For more information about diabetes, see CDC's Diabetes Program Web site.

No Tobacco

Smoking injures blood vessels and speeds up the process of hardening of the arteries. Further, smoking is a major risk for heart disease and stroke. If you don’t smoke, don’t start. Quitting smoking lowers one’s risk of heart attack and stroke. Your doctor can suggest programs to help you quit smoking. For more information about tobacco use and quitting, see CDC's Tobacco Intervention and Prevention Source Web site.

Medications

If you develop high blood pressure, your doctor may prescribe medications, in addition to lifestyle changes, to help bring it under control. Once your blood pressure is controlled continuing your medication and doctor visits is critical to keep your blood pressure in check. The lifestyle changes noted above are just as important as taking your medicines as prescribed.

Genetic Factors

Genes can play a role in high blood pressure. It is also possible that an increased risk of high blood pressure within a family is due to factors such as a common sedentary lifestyle or poor eating habits. Therefore, lifestyle factors should be considered for preventing and controlling high blood pressure. Find out more about genetics and diseases on CDC's Genomics and Disease Prevention Web site.

Related Guidelines and Recommendations

* The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure - From the National Heart, Lung, and Blood Institute Web site.

* Your Guide to Lowering Blood Pressure - From the National Heart, Lung, and Blood Institute Web site.

* Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults - From the National Heart, Lung, and Blood Institute Web site.

* Physical Activity and Health: A Report of the Surgeon General - This report brings together, for the first time, what has been learned about physical activity and health from decades of research.

* Dietary Guidelines for Americans 2005 - Dietary Guidelines for Americans is published jointly every 5 years by the Department of Health and Human Services (HHS) and the Department of Agriculture (USDA).

* The Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents - From the National Heart, Lung, and Blood Institute Web site.

* Surgeon General's Reports Related to Tobacco Use - List of reports concerning smoking and health, including reports on tobacco use among ethnic groups and young people.