High Blood Pressure
Alternate Names : Hypertension
Blood pressure is
expressed in millimeters of mercury, or mm Hg. High blood pressure is defined
as a systolic blood pressure
reading greater than 140 mm Hg or a diastolic blood pressure reading greater
than 90 mm Hg.
The systolic blood pressure is the top number of a blood pressure
shows the maximum pressure in the blood vessels. Pressure is highest as the heart contracts and
circulates blood throughout the body. The diastolic blood pressure is the
bottom number of a blood
pressure reading. It shows the lowest pressure in the blood vessels. Pressure is lowest between
heartbeats, when the heart is at rest.
The National Institutes of Health has further defined
high blood pressure. These categories are for people 18 years and older who do
not take medication for high blood pressure and do not have a short-term
serious illness. These categories are as follows.
Normal blood pressure is a systolic blood pressure of less than 130, and a
diastolic pressure of less than 85.
High normal blood pressure is a systolic blood pressure of 130 to 139, and a
diastolic pressure of 85 to 89.
Stage 1 high blood pressure is a systolic blood pressure of 140 to 159, and a
diastolic pressure of 90 to 99.
Stage 2 high blood pressure is a systolic blood pressure of 160 to 179, and a
diastolic pressure of 100 to 109.
Stage 3 high blood pressure is a systolic blood pressure of 180 or higher,
or a diastolic blood pressure of 110 or higher.
What is going on in the body?
The heart, blood vessels, brain, and kidneys control blood pressure. Blood
pressure is also controlled by the amount of fluid and salt in the body.
Certain hormones in the body can affect both blood vessels and body
fluids. The force of the contraction of the heart can also affect blood
In most people who have high blood pressure, the cause is unknown. In this case,
high blood pressure is called primary, or essential, hypertension.
What are the causes and risks of the condition?
Ninety to 95% of the time, high blood pressure is labeled as essential
hypertension. This means that the cause is unknown. The American Heart Association
has identified both controllable and noncontrollable risk factors for high blood
Uncontrollable risk factors for high blood pressure include age, heredity, and race. In men, high blood pressure occurs most often between 35 and 50 years
of age. In women, it generally starts after menopause. An individual is more likely to develop high blood pressure if
his or her parents or close relatives have it. Certain races have a higher incidence of high blood pressure. For example, African Americans develop high blood pressure earlier
and more often than Caucasians.
Controllable risk factors for high blood pressure include the following:
diet high in sodium
excess or frequent consumption of alcohol
lack of exercise
stress that is not
Secondary high blood pressure is caused by one of the following conditions:
acute lead poisoning
cocaine and other illegal drugs
disease, such as
coarctation of the aorta
hormonal abnormalities, such as a hyperactive condition of the adrenal
glands known as Cushing's
injury or radiation
therapy to the kidneys
kidney disease, such as
polycystic kidney disease
medications, such as corticosteroids
oral contraceptives, or birth control pills
tumors of the adrenal gland, such as a pheochromocytoma