BLOOD PRESSURE LEVELS

Blood pressure is measured in millimeters of mercury (mm Hg). The classifications in the table below are for adults age 18 years and older, who are not taking antihypertensive (blood pressure-lowering) drugs and aren't acutely ill.

Why is high blood pressure harmful?

High blood pressure makes your heart work harder than normal. Both the heart and arteries are then more prone to injury. High blood pressure increases the risk of heart attacks, strokes, kidney failure, eye damage, congestive heart failure and fatty buildups in arteries called atherosclerotic plaques. If you have high blood pressure, are obese, smoke, or have high blood cholesterol levels or diabetes, your risk of heart attack or stroke goes up several times.

If high blood pressure isn't treated, your heart may have to work harder and harder to pump enough blood and oxygen to your body's organs and tissues. A heart forced to work harder for a long time tends to enlarge and weaken. A slightly enlarged heart may work well, but one that's enlarged a lot has a hard time doing its job.

High blood pressure also hurts arteries and arterioles, the very small arteries that connect larger arteries to the tiny capillaries. They eventually become scarred, hardened and less elastic.

For some people, all of the above will not be adequate to get their blood pressure where needs to be. If that's true for you, you'll probably need medication. People with high blood pressure should also quit smoking because smoking greatly increases the risk of heart disease.

What factors increase a person's risk of developing high blood pressure?

Medical science doesn't understand what causes most cases of high blood pressure, so it's hard to say how to prevent it. Several factors may contribute to it.

• Heredity. People whose parents have high blood pressure are more likely to develop it than those whose parents don't.
• Race. African Americans are more likely to have high blood pressure than Caucasians are.
• Male sex. Men have a greater risk of high blood pressure than women until age 55, when their respective risks are similar. At age 75 and older, women are more likely to develop high blood pressure than men are.
• Increasing age. Blood pressure tends to increase with age, and older people are more likely to have high blood pressure.
• Sodium (salt) sensitivity.
• Obesity and overweight. If you are overweight, get down to where you should be. Blood pressure will normally drop with weight loss.

• Sedentary or inactive lifestyle. Physical inactivity is an independent risk factor for heart disease. So even if you are not overweight, get active or stay active. An inactive lifestyle also tends to contribute to obesity, a risk factor for both high blood pressure and heart disease. Regular physical activity helps control weight and lower blood pressure. Try to get at least 30 minutes of moderate to vigorous physical activity on most days.

• Heavy alcohol consumption. Experts recommend that drinkers limit themselves to no more than 1-2 drinks per day. .  Since alcoholic drinks are high in non-nutritious calories, stay away from alcohol entirely if you're trying to lose weight.

• Diabetes mellitus, gout and kidney disease. People with these conditions have a higher frequency of high blood pressure.
• Pregnancy.
• Use of some oral contraceptives and some other medications.

How does medicine help control high blood pressure?

Medicines called antihypertensives lower high blood pressure. Some, called diuretics or "water pills," rid the body of excess fluids and salt (sodium). Others, called beta blockers, reduce the heart rate and the heart's output of blood.

Vasodilators (vas"o-di-LAT'orz) are another useful group of drugs. These can cause the muscle in blood vessel walls to relax, allowing the vessel to dilate (widen). They're especially effective in the arterioles, the very small arteries that connect larger arteries to the tiny capillaries.

Other drugs for high blood pressure are the angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor blockers and the calcium antagonists (calcium channel blockers). The ACE inhibitors interfere with the body's production of angiotensin II, a chemical that causes the arteries to constrict. The angiotensin II receptor blockers block the effects of angiotensin II. The calcium antagonists can decrease the heart's pumping strength and relax blood vessels.

In most cases these drugs lower blood pressure. Quite often, however, people respond very differently to them. That's why most patients must go through a trial period to find out which medications work best with the fewest side effects.