Most people have essential hypertension, which has no identifiable cause. Some think it may be due in part to a genetic predisposition. The probability of developing this condition increases with age. In the last few decades, the risk for high blood pressure has increased because of a decline in healthy life styles. In fact, nine out of 10 persons are at risk for developing hypertension after age 50.
In approximately 5–10 percent of patients, a secondary cause exists. Secondary causes include certain types of kidney disease, abnormal functioning of certain glands (adrenal glands, thyroid gland, parathyroid glands), chronic intake of certain substances and medications (e.g., alcohol, steroids), and the presence of a rare tumor (e.g., pheochromocytoma, which secretes adrenaline-like substances). Recent studies have shown that a high intake of sodium combined with a low intake of potassium may increase the risk for high blood pressure.