 From VOA Learning English this is the health report. The heart is our life force. It pumps blood which carries oxygen to every organ in the body. As the blood flows through the blood vessels it puts pressure on the vessel walls. That pressure is often measured when you go to see a doctor or other health care worker. Blood pressure readings are often taken with a cuff tightened around the upper arm. Blood pressure is measured using two numbers. The first or upper number is called the systolic pressure. The lower number is the diastolic pressure. The upper number shows the pressure inside the blood vessels when the heart is pumping. The lower number shows the pressure when the heart rests between beats. Both numbers are important. Stephen Havas is with the University of Maryland School of Medicine. He says any level above 115 for the systolic pressure or 75 for the diastolic pressure doubles the risk of problems. High blood pressure known as hypertension is a major cause of heart disease, stroke, and death. The World Health Organization recently urged the medical community to strengthen efforts to prevent and control high blood pressure. WHO officials say one-third of people over the age of 25 have hypertension. Yet many do not know they have it. Often it can be difficult to identify an exact cause for a person's hypertension. With age the blood vessels can harden and affect the flow of blood. Genetics and family history have an influence too. But being overweight, smoking, or eating foods that contain a lot of salt can also cause blood pressure to rise. For VOA Learning English, I'm Alex Villareal.