|
Two
forms of high blood pressure have been described--essential (or
primary) hypertension and secondary hypertension. Essential
hypertension is a far more common condition and accounts for 95% of
hypertension. The cause of essential hypertension is multifactorial,
that is, there are several factors whose combined effects produce
hypertension. In secondary hypertension, which accounts for 5% of
hypertension, the high blood pressure is secondary to (caused by) a
specific abnormality in one of the organs or systems of the body.
(Secondary hypertension is discussed further in a separate section
below.)
Essential
hypertension affects approximately 75 million Americans, yet its
basic causes or underlying defects are not always known.
Nevertheless, certain associations have been recognized in people
with essential hypertension. For example, essential hypertension
develops only in groups or societies that have a fairly high intake
of salt, exceeding 5.8 grams daily. In fact, salt intake may be a
particularly important factor in relation to essential hypertension
in several situations. Thus, excess salt may be involved in the
hypertension that is associated with advancing age, African
American
background, obesity, hereditary (genetic)
susceptibility, and kidney
failure
(renal insufficiency).
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. (These identified genetic disorders are actually
considered secondary hypertension.) (High Blood Pressure, Dwight
Makoff, M.D.)
|