High blood pressure is one of the leading causes of heart attack and stroke in the United States. So what exactly is it that causes high blood pressure?

There are basically two forms of high blood pressure, primary hypertension and secondary hypertension. Primary hypertension is much more common and accounts for 95% of all the high blood pressure cases reported. There are several factors that contribute to primary hypertension. In secondary hypertension the cause is from a specific abnormality in one of the organs in the body.

Primary hypertension affects about 75 million Americans. However, its basic causes and underlying effects are not always known or easy to diagnose. In spite of this there are certain factors that are common in most cases of primary hypertension.

One factor is that the majority of people who suffer from primary hypertension get too much salt in their diet. Many live in fast food restaurants where they serve French fries loaded with salt and also put a salt shaker to just about everything they eat. Their salt intake usually exceed 5.8 grams daily.

Genetic factors also play an important role in primary hypertension. However, the exact genes that make a person likely to develop hypertension because of these genetic factors have yet to be identified. Genes are portions of chromosomes that that produce the proteins that determine the individual characteristics of each person. Research in this area of the disease is focused on the genetic factors that affect the renin-angiotensin-aldosterone system. This system helps to regulate blood pressure by controlling salt balance and the state of elasticity of the arteries.

About 30% of the cases of primary hypertension are because of genetic factors, meaning that in spite of the person's diet and exercise routine they would have most likely gotten high blood pressure because of these genes. For example, in the United States, high blood pressure seems to be more common in people of African heritage. Asians have the lowest rate of high blood pressure. Also, if a person has two parents who suffer from primary hypertension, that person is more likely to develop the condition as well. Rarely do unusual genetic disorders lead to primary hypertension. These cases are usually identified as secondary hypertension.

Most people who suffer from primary hypertension have in common a particular abnormality of the arteries. This common abnormality is that they have an increased resistance in the arteries, meaning they are not as elastic as they should be, especially in the tiny arteries that are farthest away from the heart.

People who are most likely to have this abnormality are usually those who are overweight, don't exercise, use too much salt, and are aging. Inflammation may also be a contributing cause of primary hypertension, which is indicated by an elevated C reactive protein level.

In our next article in this series on high blood pressure we'll discuss the contributing factors to secondary hypertension.