A blood pressure of 140/90 or higher is considered high blood pressure. Both numbers are important. If one or both numbers are usually high, you have high blood pressure. If you are being treated for high blood pressure, you still have high blood pressure even if you have repeated readings in the normal range.
Causes
About 90% to 95% of hypertension cases, called primary, or essential hypertension, have no known cause. Primary hypertension may be influenced by factors such as genetic makeup, weight, or salt intake. Research is underway to learn more about the role that genes play in hypertension, as well as to explore the association between hypertension and factors such as obesity, low birth weight, and low levels of nitric oxide. Nitric oxide is a molecule that affects the smooth muscle cells that line blood vessels. People with low levels of nitric oxide have been found to have high blood pressure; especially African-Americans with low levels of the molecule.
Family Ties to PPH Studies show that at least 15 to 20% of patients with primary pulmonary hypertension have an inherited form of the disease. It is unclear whether it is a sporadic gene defect in these families.
Two main types of hypertension are recognized. By far the most common is Essential Hypertension, sometimes called Primary Hypertension. This is hypertension in which there is no identifiable cause. Ninety five percent of all persons living with hypertension have essential hypertension. Although researchers have been unable to pinpoint its specific causes, several risk factors definitely increase an individual's chance of developing essential hypertension.
Changes in the arteries can complicate the problem. Normally the arteries are rather springy; in addition to expanding and contracting in rhythm with the heart, they adjust themselves to the volume of the blood and to other conditions within the body, stretching or tightening up as necessary to raise, lower, or maintain blood pressure. Various factors - stress, for instance - as well as diet, heredity, lifestyle, and aging, have a detrimental effect on the arteries. They become less elastic and thus less able to adjust to changes in the body; and they tend to become coated with arterial cholesterol plaque, a fatty deposit that clogs them, just as deposits in your house's pipes can cause your sink to back up.
In most people, the causes of hypertension (also known as high blood pressure) are not known. This type of high blood pressure is called primary, or essential, hypertension. In some people, the cause of hypertension is the result of another medical problem or medication. When the causes of hypertension are known, the condition is referred to as secondary hypertension.
Approximately 30% of cases of essential hypertension are attributable to genetic factors. For example, in the United States, the incidence of high blood pressure is greater among African Americans than among Caucasians or Asians. Also, in individuals who have one or two parents with hypertension, high blood pressure is twice as common as in the general population. Rarely, certain unusual genetic disorders affecting the hormones of the adrenal glands may lead to hypertension.
by james sameul
