High Blood Pressure

Nearly 1 in 3 American adults has high blood pressure (hypertension). Once high blood pressure develops, it usually lasts a lifetime. The good news is that it can be treated and controlled.

Definitions

Each time your heart beats, it pumps blood through the blood vessels, or arteries, that run through your body. Blood pressure is the force of the blood pushing against the walls of the arteries. Your blood pressure is at its highest when the heart beats, pumping the blood. This is called systolic pressure. When the heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure.

Blood pressure is always given as these two numbers, the systolic and diastolic pressures. Both are important. Usually they are written one above or before the other, such as 120/80 mmHg (measured in millimeters of mercury, a unit for measuring pressure). When the two measurements are written down, the systolic pressure is the first or top number, and the diastolic pressure is the second or bottom number (for example, 120/80). If your blood pressure is 120/80, you say that it is "120 over 80."

Blood pressure changes during the day. It is lowest as you sleep and rises when you get up. It also can rise when you are excited, nervous, or active.

Still, for most of your waking hours, your blood pressure stays pretty much the same when you are sitting or standing still. That level should be lower than 120/80 mmHg. When the level stays high, 140/90 mmHg or higher, you have high blood pressure. With high blood pressure, the heart works harder, your arteries take a beating, and your chances of a stroke, heart attack, and kidney problems are greater.

A blood pressure reading below 120/80 mmHg is considered normal. In general, lower is better. However, blood pressure lower than 90/60 mmHg can be a cause for concern and should be checked out by a doctor.

Doctors classify blood pressures under 140/90 mmHg as either normal or prehypertension. If your blood pressure is in the prehypertension range, it is more likely that you will end up with high blood pressure unless you take action to prevent it.

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 high blood pressure.

There is an exception to the above definition of high blood pressure. A blood pressure of 130/80 mmHg or higher is considered high blood pressure in people with diabetes and chronic kidney disease.

About two out of every three people over the age of 60 who have high blood pressure have isolated systolic hypertension. This means that only the top number, the systolic pressure, is high (140 mmHg or higher). Isolated systolic hypertension can be as harmful as when both numbers are high.

Symptoms and Diagnosis

High blood pressure is called the silent killer because it usually has no symptoms. Some people may not find out they have it until they have trouble with their heart, brain, or kidneys. When high blood pressure is not found and treated, it can cause:

• The heart to get larger, which may lead to heart failure.
• Small bulges (aneurysms) to form in blood vessels. Common locations are the main artery from the heart (aorta); arteries in the brain, legs, and intestines; and the artery leading to the spleen.
• Blood vessels in the kidney to narrow, which may cause kidney failure.
• Arteries throughout the body to "harden" faster, especially those in the heart, brain, kidneys, and legs. This can cause a heart attack, stroke, kidney failure, or amputation of part of the leg.
• Blood vessels in the eyes to burst or bleed, which may cause vision changes and can result in blindness.

The only way to find out if you have high blood pressure is to have your blood pressure measured. Blood pressure readings are usually taken when you are sitting or lying down and relaxed. Below are things you can do before getting your blood pressure taken:

• Do not drink coffee or smoke cigarettes 30 minutes before having your blood pressure taken.
• Wear short sleeves.
• Go to the bathroom before the reading. Having a full bladder can change your blood pressure reading.
• Sit for 5 minutes before the test.

Some people's blood pressure is high only when they visit the doctor's office. This condition is called white coat hypertension. If your doctor suspects this, you may be asked to check and record your blood pressure at home with a home monitor. Another way to check blood pressure away from the doctor's office is by using an ambulatory blood pressure monitor. This device is worn for 24 hours and can take blood pressure every 30 minutes. 

Causes

Hypertension can be divided into two types: essential (or primary) hypertension and secondary hypertension. If hypertension is caused by other diseases and the high blood pressure is gone after these diseases are cured, then the hypertension is the secondary hypertension. If hypertension is not caused by other diseases, it is the essential hypertension.

The causes of essential hypertension are not well understood. However, it is known that salt, or sodium ions, plays an important role. Higher salt intake will increase the risk of developing hypertension. Many genes that have been found to be associated with hypertension are involved in the processing of sodium ions (more info).

Reference:

National Heart, Lung, and Blood Institute, USA.