context: About one in three adults in the U. S. have high blood pressure. More than 90% of adults who survive into their 80s will develop elevated blood pressure -- also called hypertension -- and about 50% of people will have it by age 60. Although high blood pressure is common, it's not harmless. High blood pressure is a major cause of atherosclerosis, the artery-clogging process that leads to heart attacks and strokes. Blood pressure higher than 130/80 is seen in: 69% of people who have their first heart attack 77% of people who have their first stroke 74% of people who have congestive heart failure High blood pressure usually has no symptoms, even if it is severely elevated. Only 35% of people with high blood pressure have it under control. If you're one of the millions of people with uncontrolled hypertension, your arteries may be paying the price. Blood pressure is the pressure inside the arteries. It's reported in two numbers; for example, "125 over 80." What do these numbers mean? The top number is the systolicblood pressure. This is the peak pressure, when the heart pumps and expands the arteries. The bottom number is the diastolicblood pressure. When the heart relaxes, the pressure in the arteries falls to this value. Normal blood pressure is less than 120 over less than 80. Treatment is recommended for blood pressure above 130 over 80 for most people. Treatment may be considered at lower levels, depending on other medical conditions you may have. When the heart beats, it pushes blood through the arteries in your entire body. Higher blood pressures mean that with each beat, arteries throughout the body swell and stretch more than they would normally. This stretching can injure the endothelium, the delicate lining of all arteries, causing arteries to become stiffer over time. Healthy endothelium actively works to prevent atherosclerosis -- also called hardening of the arteries -- from developing. Injured endothelium, on the other hand, allows more "bad" LDL cholesterol and white blood cells to enter the lining of the artery. The cholesterol and cells build up in the artery wall, eventually forming the plaque of atherosclerosis. Plaque is dangerous. Although it often grows without symptoms for years, plaque can suddenly rupture, forming a blood clot that blocks the artery, which keeps oxygen from getting to the heart muscle or the brain. The result can be a heart attack or stroke. Because high blood pressure increases the risk of atherosclerosis, it raises the chance of developing all the complications of atherosclerosis, such as: Heart attack Stroke Peripheral arterial disease Erectile dysfunction Kidney disease When it comes to causing atherosclerosis, though, high blood pressure rarely acts alone. High blood pressure in isolation increases the risk of atherosclerosis, but it's particularly dangerous when it in combination with: Diabetes Abnormal cholesterol levels Cigarette smoking If you have any of these other risk factors and hypertension, your risk of atherosclerosis begins to rise dramatically. Treating high blood pressure can provide dramatic protection against atherosclerosis. Much of the decline in the death rate from heart attacks and strokes is due to improved treatment of high blood pressure over the past 50 years. For example, in middle-aged and older adults with high blood pressure, lowering systolic blood pressure (the top number) by 10 points leads to: 50% to 60% lower risk of dying from stroke 40% to 50% lower risk of death from a heart attack Exercise and a low-salt diet that is high in fruits and vegetables will reduce blood pressure by a moderate amount. Weight management is also important in maintaining a healthy blood pressure. For most people, though, medication is necessary to adequately control high blood pressure. In fact, most people will eventually require two or more drugs for blood pressure. Numerous drugs effectively treat hypertension. No particular medicine has been proven better than the others at preventing atherosclerosis. High blood pressure is the most common of the risk factors for atherosclerosis. It's also easily detectable and treatable. Most drugstores and almost all fire stations provide free blood pressure checks, and good medications that you can take without side effects or complications are available. Don't fly blind: get checked, know your numbers, and get treated if you have hypertension.