context: Also known as hypertension, high blood pressure is the most common cardiovascular disease. Blood pressure is the force of blood pushing against your artery walls as it goes through your body. Like air in a tire or water in a hose, blood fills your arteries to a point. Just as too much air pressure can damage a tire, or too much water pushing through a garden hose can damage the hose, high blood pressure can hurt your arteries and lead to life-threatening conditions like heart disease and stroke. In the U. S. alone, about 30% of adults have high blood pressure. If you have it, you'll probably find out about it during a regular checkup. Or, you may have noticed a problem while taking your own blood pressure. If that's you, be sure to see your doctor to find out for sure. He can also show you what you can do about it. A reading appears as two numbers. The first, the higher of the two, is your systolic pressure. That's the force in the arteries when the heart beats. The second number is your diastolic pressure, or the pressure in the arteries when the heart rests between beats. Normal blood pressure goes up from about 64/40 at birth to about 120/80 in a healthy adult. If someone were to take your blood pressure right after you gave a speech or jogged 5 miles, it'd probably be slightly high. This isn't necessarily cause for alarm: It's natural for blood pressure to rise and fall with changes in activity or emotional state. It's also normal for blood pressure to vary from person to person, even from one area of the body to another. But if your blood pressure stays high, you should talk with your doctor about treatment. Hypertension forces the heart to work far beyond its capacity. Along with injuring blood vessels, it can damage your brain, eyes, and kidneys. People with readings of 130/80 or higher, on at least two occasions, are said to have high blood pressure. If yours is 180/120 or higher, get medical attention right away. Your doctor could also tell you that you have something called prehypertension. That's when your BP is just a bit higher than 120/less than 80. About 75 million Americans fall into this category. Prehypertension can raise your chance of damage to your arteries, heart, brain, and kidneys. Many doctors say prehypertension should be treated. Still, there's no evidence that it provides long-term help. Many people who have high blood pressure don't realize they have it. It's often called "the silent killer" because it rarely causes symptoms, even as it causes serious damage to the body. Left untreated, hypertension can lead to serious problems, such as: Vision problems Heart attack Stroke Kidney failure Heart failure Critically ill patients who have very high blood pressure may have "malignant hypertension." It's a dangerous condition that can develop rapidly and damage your organs quickly. If you have it, you should see your doctor right away. Fortunately, high blood pressure can be controlled. The first step is to have your blood pressure checked regularly. High blood pressure is more likely in people with a family history of high blood pressure, heart disease, or diabetes. It's also more common in people who are: African- American Older than 55 Overweight Inactive Heavy alcohol drinkers Smokers If you eat foods high in salt, or use medications like NSAIDs (such as ibuprofen and aspirin), decongestants, and illicit drugs such as cocaine, you also have a higher chance of getting high blood pressure. In as many as 95% of reported high blood pressure cases in the U. S., the underlying cause can't be determined. This is essential hypertension. High blood pressure tends to run in families. Age and race also play a role. More than 40% of all African- Americans in the U. S. have high blood pressure. Diet and lifestyle also play a big role in essential hypertension. The link between salt and high blood pressure is especially noteworthy. People living on the northern islands of Japan eat more salt than anyone else in the world. They're also most likely to get hypertension. Many people with high blood pressure are "salt sensitive." That means anything more a minimal amount will raise their blood pressure. Other things associated with essential hypertension include: Obesity Diabetes Stress Low levels of potassium, calcium, and magnesium Lack of physical activity Heavy alcohol use When a direct cause for high blood pressure can be identified, that's secondary hypertension. Kidney disease is the most common cause. Hypertension can also be brought on by tumors or conditions that cause the adrenal glands (the small glands that sit atop your kidneys) to release large amounts of hormones that raise blood pressure. Birth control pills -- specifically those that have estrogen -- and pregnancy can boost blood pressure. Other medicines can, too. Check with your doctor to see if anything you take may cause your numbers to go up.