Every time your heart beats, it pumps blood through all of your body's arteries, veins and capillaries. If these blood vessels are narrow, it's harder for blood to flow through them and the pressure against the walls increases. This can cause high blood pressure.

According to recent estimates, nearly one in three U.S. adults has high blood pressure, but because there are no symptoms, nearly one-third of these people don't know they have it. In fact, many people have high blood pressure for years without knowing it. High blood pressure is a threat because it makes the heart work harder, increasing its oxygen demands and contributing to angina (chest pain related to heart disease). Unchecked, high blood pressure increases the risk of heart attacks, stroke and kidney disease. This is why high blood pressure is often called the "silent killer." The only way to tell if you have high blood pressure is to have your blood pressure checked.

Medical science doesn't understand why most cases of high blood pressure occur, so it's hard to say how to prevent it. However, we do know that several factors may contribute to high blood pressure and raise your risk for heart attack and stroke