The most comprehensive and systematic analysis of causes of death ever done, “The Global Burden of Disease” study, discovered that the No. 1 killer risk factor in the world is high blood pressure. Stealthily, this “silent killer” lays to waste 9 million people year after year. Here in the United States high blood pressure affects nearly 78 million — that’s one in three of us. It is called “the silent killer” because it typically has no symptoms until it has already significantly damaged the heart and arteries.