There are two types of high blood pressure. Primary, or “essential,” high blood pressure is by far the most common, affecting an estimated 90 to 95 percent of those with high blood pressure. Most likely, this is the form you have. This is also the type for which no specific cause is known, although researchers do have some theories.
One of the main theories is that primary high blood pressure is the result of a hyperactive sympathetic nervous system, which controls involuntary actions, such as breathing, blinking, and pushing blood through the body. Other theories blame hormonal imbalances and damage to the endothelium, the inner layer of blood vessels, which prevents them from dilating. In addition, mutations in the genes that control blood volume and sodium; low intake of micronutrients such as potassium, magnesium, and calcium; and high sodium intake (the one you’re probably most familiar with), may play a role.
The other form of high blood pressure, called secondary, is a by-product of having a specific medical condition. These include kidney disease, Cushing’s syndrome (which is a rare hormonal condition), pregnancy, an overactive thyroid gland, and neurological disorders. In addition, certain medicines can cause secondary high blood pressure, such as high doses of estrogen, corticosteroids, and nonsteroidal anti-inflammatory drugs.
High blood pressure is actually a fairly modern illness; 100 years ago, it, like most chronic heart conditions, barely existed. That’s because few people were overweight, and most got plenty of physical activity and ate diets that were relatively healthy, with few processed foods.