Also known as high blood pressure, a condition in which too much force is exerted by the blood as it travels through the body's arteries.

There are two types of hypertension: primary and secondary. Primary, or essential, hypertension is caused by external factors; secondary hypertension is related to an underlying disorder, such as a congenital heart defect or kidney disease. Factors that increase the risk of high blood pressure include age (the likelihood of hypertension increases with age), race (hypertension is two to three times more common in blacks than in whites), heredity, and being overweight.

About 60 million Americans have high blood pressure. Of this number roughly 2.7 million are children between the ages of six and 17. Secondary hypertension occurs in only about 10% of the diagnoses—in the majority of cases the condition has no known cause. However, serious hypertension in infants and young children is usually of the...