High Blood Pressure

When the heart beats, it pumps blood to the arteries and creates pressure in them. This pressure (blood pressure) results from two forces. The first force is created as blood pumps into the arteries and through the circulatory system. The second is created as the arteries resist the blood flow.

If you're healthy, your arteries are muscular and elastic. They stretch when your heart pumps blood through them. How much they stretch depends on how much force the blood exerts.

Your heart beats about 60 to 80 times a minute under normal conditions. Your blood pressure rises with each heartbeat and falls when your heart relaxes between beats. Your blood pressure can change from minute to minute, with changes in posture, exercise or sleeping, but it should normally be less than 120/80 mm Hg (millimeters of mercury) for an adult. Blood pressure that stays between 120–139/80–89 is considered prehypertension and above this level (140/90 mm Hg or higher) is considered high (hypertension). Your doctor may take several readings over time before deciding whether your blood pressure is high.

What do blood pressure numbers indicate?

• The higher (systolic) number represents the pressure when the heart is beating.
• The lower (diastolic) number represents the pressure when the heart is resting between beats.

The systolic pressure is always stated first and the diastolic pressure second. For example: 118/76 (118 over 76); systolic = 118, diastolic = 76.

Controllable risk factors

• Obesity — People with a body mass index (BMI) of 30.0 or higher are more likely to develop high blood pressure.
• Eating too much salt — A high sodium intake increases blood pressure in some people.
• Drinking too much alcohol — Heavy and regular use of alcohol can increase blood pressure dramatically.
• Lack of physical activity — An inactive lifestyle makes it easier to become overweight and increases the chance of high blood pressure.
• Stress — This is often mentioned as a risk factor, but stress levels are hard to measure, and responses to stress vary from person to person.

Uncontrollable risk factors

• Race — Blacks develop high blood pressure more often than whites, and it tends to occur earlier and be more severe.
• Heredity — If your parents or other close blood relatives have high blood pressure, you're more likely to develop it.
• Age — In general, the older you get, the greater your chance of developing high blood pressure. It occurs most often in people over age 35. Men seem to develop it most often between age 35 and 55. Women are more likely to develop it after menopause.