High blood pressure, or hypertension, is the most common major health condition in the United States. It is one of the leading causes of heart attack, heart failure, stroke, kidney failure, and premature death. It also can damage parts of the circulatory system—including blood vessels in the heart, brain, eyes, and kidneys.

Sometimes called the “silent killer,” high blood pressure is a disease that can go undetected for years. The higher the blood pressure or the longer it goes undiagnosed, the worse the outlook. More than 50 million Americans have high blood pressure. Of that number, an estimated one-third do not know they have the disease.

There has been remarkable progress in detecting, treating, and controlling high blood pressure. Recently, there has been a substantial increase in the number of individuals who are aware of their high blood pressure and who are being treated for it.

At the same time, the incidences of coronary artery disease and stroke have significantly decreased, partially as a result of progress in the detection, treatment, and control of high blood pressure. Despite these efforts, most people with high blood pressure do not have adequately controlled blood pressure.

Unfortunately, high blood pressure remains a serious medical problem. Approximately 5 percent of cases of high blood pressure can be traced to underlying diseases, such as kidney disorders or conditions that cause narrowing of the arteries. This is called “secondary hypertension.” But most cases have no known cause. This type is called “primary” or “essential” hypertension.

There are risk factors that indicate a predisposition for the development of high blood pressure. Among these risk factors are the following: Family history—A family history of high blood pressure is a risk for hypertension. Age—High blood pressure becomes more common among all people as they grow older.

After all, nearly twothirds of Americans aged 70 or older have the disease. Sex—Although men and women are typically equally affected, women who use birth control pills and smoke cigarettes have a greater chance of having high blood pressure.

Race—As an example, high blood pressure is more common among blacks than whites. You either have or don’t have the above risk factors. There are also other factors that increase your risk for high blood pressure which you can do something about:

• Obesity—control your weight
• Lack of exercise—get moving
• Alcohol consumption—take control or abstain
• Excessive salt (sodium) intake—cut down

Blood pressure is the force that the blood exerts on the artery walls as the heart pumps it through the body. The amount of force depends on various factors, including how hard the heart pumps and the volume of blood it pumps.

Another factor is the amount of resistance blood encounters in the arteries—the thicker or more clogged the blood vessels, the greater the resistance. The elasticity of arteries also plays a role in blood pressure. The less elastic arteries are, the less they expand under the force of a heartbeat and the higher the resistance.

The standard way to measure blood pressure is in millimeters of mercury (mm Hg). This unit of measurement refers to how high the pressure inside the arteries is able to raise a column of mercury.

Each blood pressure measurement has two numbers. The top number is the systolic blood pressure, or the highest pressure within the arteries that occurs during “systole,” when the heart is contracting.

The bottom number is the diastolic blood pressure, or the lowest pressure within the arteries that occurs during “diastole,” when the heart is relaxed and filling with blood. For most people, a blood pressure of 120/80 mm Hg or lower is considered healthy.

Effects of High Blood Pressure

Repeated blood pressure measurements that are more than 130/85 mm Hg indicate a potential for problems, a greater risk of progressing to definite high blood pressure, and the need to have regular blood pressure checks.

A measurement of 140 systolic or more, 90 diastolic or more, or both indicates high blood pressure, which requires treatment. Recent guidelines stress the importance of treating to achieve a pressure less than 130/85.

Indeed, treating to these lower levels of blood pressure further reduces the incidence of stroke, heart and kidney damage, and other vascular problems. When high blood pressure occurs, it means that the force of the blood in the arteries is excessive and many health complications can occur.

• Heart: High blood pressure forces the heart to work harder than it should to pump blood to distant tissues and organs. Another way to understand blood pressure is to think of it as a weight or a load that the heart muscle must “push” against.

Like any muscle, the heart gets larger with pushing heavy weights. Eventually, the heart’s pumping efficiency decreases when the muscle can no longer adapt to the excessive workload that the high blood pressure demands. When this occurs, the heart muscle may weaken and the heart can fail.

• Arteries: High blood pressure can also accelerate the development of plaque within the arteries, a condition known as atherosclerosis. With the narrowing of the artery walls, the risk of heart attack is increased. High blood pressure also can lead to bulges (aneurysms) in the arteries. If an aneurysm in a major artery ruptures, the results can be catastrophic and possibly fatal.

• Brain: High blood pressure increases the risk of having a stroke, which occurs when a blood vessel within the brain either ruptures or is blocked.

• Kidneys: The kidneys filter waste products from the blood and maintain proper blood minerals and blood volume. When these functions are impaired or compromised, so is their role in helping to maintain blood pressure. These effects can produce a destructive cycle that results in increasing blood pressure and a gradual failure of the kidneys to remove impurities from the blood.

• Eyes: High blood pressure often causes problems with the eyes. Examination of the retina can reveal narrowing of the arteries, small hemorrhages, and accumulations of protein that have leaked from affected blood vessels (exudates).

Although it is unusual for high blood pressure to impair vision, it can occur as a result of severe constriction of the retinal arteries and swelling (edema) of the retina during episodes of increased blood pressure. Treating the high blood pressure is the only way to reverse this vision loss.