What Is High Blood Pressure?

by National Institute on Aging

Each time your heart beats, it pumps oxygen-rich 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.

The pressure of blood against the artery walls when your heart beats is called systolic pressure. The pressure between beats when your heart relaxes is called diastolic pressure.

Blood pressure is always given as two numbers, the systolic and diastolic pressures. Both are important. Usually they are written one above or before the other - for example, 120/80 mmHg. The top, or first, number is the systolic and the bottom, or second number, is the diastolic. If your blood pressure is 120/80, you say that it is "120 over 80."

Your blood pressure changes throughout the day. It is lowest when you're asleep, and it rises when you awaken. It also can rise when you are excited, nervous, or active. So it varies throughout the day.

A systolic blood pressure of 140 mmHg or higher, or a diastolic blood pressure of 90 mmHg or higher, is considered high blood pressure, or hypertension. Hypertension is the medical term for high blood pressure.

If you have diabetes or chronic kidney disease, a systolic blood pressure of 130 mmHg or higher, or a diastolic blood pressure of 80 mmHg or higher is considered high blood pressure.

High blood pressure currently affects more than 65 million Americans. That's 1 in every 3 adults.

High blood pressure is often called "the silent killer" because it usually has no symptoms. Some people may not find out they have high blood pressure until they have trouble with their heart, brain, or kidneys. When high blood pressure is not diagnosed and treated, it can lead to other life-threatening conditions, including heart attack, stroke, and kidney failure.

High blood pressure can cause

Your heart to work too hard and become larger, which can lead to heart failure.

Small bulges (aneurysms) to form in your blood vessels. Common locations for aneurysms are the aorta, which is the main artery from the heart; the arteries in your brain, legs, and intestines; and the artery leading to your spleen.

High blood pressure can cause

blood vessels in your kidneys to narrow, which can cause kidney failure, and blood vessels in your eyes to burst or bleed, which may cause vision changes and can result in blindness.

arteries throughout your body to "harden" faster, especially those in your heart, brain, kidneys, and legs. This can cause a heart attack, stroke, or kidney failure, or lead to amputation of part of the leg.

A blood pressure reading of 120/80 mmHg or less is considered normal. Usually, the lower, the better, although very low blood pressure can sometimes be a cause for concern and should be checked out by your doctor.

If either your systolic or diastolic blood pressure is higher than normal (120/80) but not high enough to be considered high blood pressure (140/90), you have pre-hypertension. Pre-hypertension is a top number between 120 and 139 or a bottom number between 80 and 89 mmHg. For example, blood pressure readings of 138/82, 128/70, or 115/86 are all in the "pre-hypertension" range.

If you have pre-hypertension, your chances of developing high blood pressure are greater than average unless you take action to prevent it. In fact, having pre-hypertension doubles a woman's chances of having heart disease or a stroke. That's a 100 percent increase. For men, the increase is 45 percent.

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.

You may have isolated systolic hypertension and feel fine. As with other types of high blood pressure, it often causes no symptoms.

When your systolic and diastolic pressures fall into different categories, the higher category is used to classify your blood pressure level. For example, 160/80 mmHg is considered stage 2 high blood pressure even though a diastolic pressure of 80 mmHg is in the pre-hypertension range.

Quiz

1. Blood pressure changes throughout the day. It

A. is highest while you sleep.
B. rises when you awaken.
C. is lower when you take a bath.

B is the correct answer. Your blood pressure is lowest when you are sleeping and rises when you awaken.

2. Blood pressure is measured in an upper number and lower number. These are called:

A. systolic and diastolic.
B. numerator and denominator.
C. a ratio.

A is the correct answer. Blood pressure is always given as two numbers, the systolic and diastolic pressures. Both are important. Usually they are written one above or before the other - for example, 120/80 mmHg. The top, or first, number is the systolic and the bottom, or second number, is the diastolic. If your blood pressure is 120/80, you say that it is "120 over 80."

3. A blood pressure reading below 120/80 is considered

A. pre-hypertension.
B. normal.
C. too low.

B is the correct answer. A blood pressure reading below 120/80 is considered normal. In general, lower is better. However, very low blood pressures can sometimes be a cause for concern and should be checked out by a doctor.

4. If not treated, high blood pressure can lead to

A. heart failure.
B. kidney failure.
C. heart attack.
D. all of the above

D is the correct answer. If left untreated, high blood pressure can lead to heart failure, kidney failure, and heart attack.

About the Author

www.nia.nih.gov
NIA, one of the 27 Institutes and Centers of NIH, leads a broad scientific effort to understand the nature of aging and to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people.