Blood pressure is the measure of the force of blood as it travels through the arteries. It's measured at two points during the heart beat. The first reading, called the systolic pressure, is taken when the heart is beating. The second reading is the diastolic pressure. It's taken between beats, while the heart is at rest.

According to the American Heart Association, as many as 72 million adults in the U.S. have high blood pressure, or hypertension. But the condition can occur at any age. Researchers estimate up to 5 percent of American children may have high blood pressure.

One of the main risk factors for high blood pressure in kids is obesity. Risk is also higher in African-American children and those with a family history of hypertension. A personal history of kidney disease, coarctation of the aorta (a type of congenital heart defect) and endocrine disease is also associated with elevated blood pressure.

High blood pressure doesn't usually cause problems during childhood. However, kids with hypertension are at higher risk for adult hypertension and early development of heart disease and stroke. The American Heart Association currently recommends an annual blood pressure screening for all children three and older.

Teen Screening

Despite the recommendations for hypertension screening, many children with the condition aren't getting properly diagnosed. A recent study in the Journal of the American Medical Association found 74 percent of the children had undiagnosed high blood pressure.

Health experts with Hackensack University Medical Center have instituted a blood pressure screening program at Hackensack High School. The goal is to identify students who have hypertension, or who may be at risk for developing hypertension (i.e., have prehypertension).

Once a screening is performed, a letter is sent home to parents explaining the results. Pediatric Nephrologist, Leigh Ettinger, M.D., says teens with high blood pressure are encouraged to see their family physician for a more thorough evaluation and, if necessary, treatment. Students with prehypertension should have their blood pressure checked every six months to make sure the condition is not progressing to hypertension. In many cases, changes in diet, increased physical activity and lifestyle modifications can bring blood pressure under control.

The blood pressure screening program currently targets students in grades 9 to 12. In the future, doctors would like to extend the screenings to middle school students. Last year, the researchers found about 4 percent of the students who were screened had hypertension. Roughly, 23 percent had prehypertension.

For general information about high blood pressure:

American Heart Association

National Heart, Lung and Blood Institute