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Definition
Blood pressure is the force of blood against the walls of the arteries. Blood pressure rises and falls during the day, and it is typically recorded as 2 numbers: the systolic pressure (the force of blood in the arteries as the heart beats) over the diastolic pressure (the force of blood in the arteries as the heart relaxes between beats).
According to The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, which was published by the NHLBI in May 2003, a normal blood pressure is defined as a SBP of less than 120 mm Hg and a DBP of less than 80 mm Hg. When blood pressure stays elevated over time, it is called high blood pressure or HTN. .
HTN is defined as a SBP of ≥140 mm Hg, a DBP of ≥90 mm Hg, or a situation in which a person is taking an antihypertensive medication. HTN is further categorized and defined as follows.
- Stage 1 HTN is defined as a SBP of 140 to 159 mm Hg or a DBP of 90 to 99 mm Hg.
- Stage 2 HTN is a SBP of 160 mm Hg or greater or a DBP of 100 mm Hg or greater.
- Prehypertension is defined as a SBP of 120 to 139 mm Hg or a DBP of 80 to 89 mm Hg.
DBP does not need to be high for a person to have high blood pressure. When only the SBP is high, the condition is called ISH. ISH is the most common form of high blood pressure in older Americans. For most Americans, SBP increases with age, whereas DBP increases until about age 55 and then declines. About 65% of persons with HTN who are more than 60 years old have ISH. If left uncontrolled, increased SBP can lead to stroke, heart attack, congestive heart failure, kidney damage, blindness, or other conditions. Although it cannot be cured once it has developed, ISH can be controlled.
However, DBP has been and remains—especially for younger persons—an important HTN number. The higher the DBP, the greater the risk for heart attacks, strokes, and kidney failure.
Incidence
High blood pressure is common, affecting more than 65 million—or 1 in 3—adults in the United States. It occurs more often among blacks than whites. High blood pressure is also more common in the southeastern United States.
The prevalence of high blood pressure increases sharply with age. The condition affects about 3% of persons between the ages of 18 and 24 years and about 70% of persons 75 years old and older.
Etiology
The causes of high blood pressure vary and may include narrowing of the arteries, a greater-than-normal volume of blood, or the heart beating faster or more forcefully than it should. Any of these conditions will cause increased pressure against the artery walls. High blood pressure may also be caused by another medical problem. Most of the time, the cause is not known.
Risk Factors
Many Americans tend to develop high blood pressure as they get older. About 60% of all Americans who are 60 years and older have HTN. However, it is important to note that HTN is not a part of healthy aging.
Other risk factors for high blood pressure include the following:
- being overweight;
- in the male gender, being over the age of 45 years;
- in the female gender, being over the age of 55 years;
- a family history of high blood pressure; and.
- prehypertension.
Other factors that can raise blood pressure include increased salt and alcohol consumption, decreased potassium consumption, a sedentary lifestyle, certain medications, and stress.
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