The Reader's Digest Association, Inc./GID
The threat to your health isn't from the high pressure itself but from the damage such pressure eventually causes to arteries and smaller blood vessels. This damage is particularly devastating to the small blood vessels in organs such as your eyes, kidneys, brain, and heart. These vessels are simply not designed to consistently withstand high levels of pressure. They cope with it by becoming more muscular, a process called hypertrophy, or enlargement of tissue. This harms the organ that contains the vessels because even though the vessels get bigger overall to handle the increased pressure, the space (or lumen) within them narrows. This narrowing makes it harder for blood to flow through the vessels, prompting the heart to work harder to push blood through. All of this further increases blood pressure, creating a dangerous cycle that continues until blood flow to the organ is compromised or the blood vessels are damaged, leading, most commonly, to kidney failure, heart attack, or stroke. Here's a short primer on the conditions strongly linked to hypertension.
Atherosclerosis. This is hardening and narrowing of the arteries caused by the slow buildup of plaque on the inside of artery walls. It can lead to several serious medical conditions, including coronary artery disease, angina, heart attack, sudden death, stroke, and transient ischemic attacks (TIA), or mini-strokes.
Cardiovascular disease (CVD). This is a catchall term for all diseases affecting the heart and blood vessels.
Coronary artery disease (CAD) or coronary heart disease (CHD). Coronary artery disease, the most common heart condition in Americans, occurs when the arteries that supply blood to the heart muscle (coronary arteries) become hardened and narrowed due to the buildup of plaque on their inner walls or lining (atherosclerosis). This in turn reduces blood flow to the heart, decreasing oxygen supply to the heart muscle. Over time, this lack of oxygen decreases the ability of the heart muscle to pump at full capacity when you're doing more than basic activities. Symptoms of CAD can include chest pain (angina) and shortness of breath with exertion.
Heart attack. Also referred to as a coronary occlusion, a heart attack occurs when the supply of blood and oxygen to an area of heart muscle is blocked, usually by a clot in a coronary artery. Unless the blockage is treated within a few hours, the affected heart muscle dies and is replaced by scar tissue.
Heart failure. This condition develops over time as the heart has increasing trouble pumping blood throughout the body. It's also known as congestive heart failure (CHF).
Stroke. There are two main types of stroke. The most common is ischemic stroke, which occurs when something suddenly blocks the blood supply to an area of the brain. The other form is hemorrhagic stroke, which occurs when a blood vessel in the brain bursts, spilling blood into the spaces surrounding the brain cells. Both lead to the death of brain cells as oxygen is cut off and result in temporary or permanent neurological damage or death.
A transient ischemic attack, or mini-stroke, is technically not a stroke but rather a neurological deficit that lasts less than 24 hours. It's caused by a temporary interruption of the blood supply to an area of the brain and should serve as a warning sign, since about one-third of those who have a TIA will have an acute stroke some time in the future.
Dementia. People with hypertension are more likely than those with normal blood pressure to experience dementia and other cognitive problems as they age. There's also some evidence that uncontrolled hypertension may increase the risk of Alzheimer's disease. Although we don't know all the reasons for the connection, one theory is that over years, hypertension decreases the elasticity of blood vessels in the brain, increasing resistance and reducing their responsiveness.
Kidney disease. Uncontrolled hypertension is the second leading cause of chronic kidney disease (diabetes is the first). It speeds the deterioration of kidney function to the point where lifesaving measures, such as dialysis or kidney transplant, are needed.
Blood vessel damage. Constant high blood pressure can damage the lining of the blood vessels. This can increase the rate at which plaque accumulates on blood vessel walls (atherosclerosis), narrowing the blood vessels and reducing the amount of blood flowing to the body's organs.
Retinopathy (eye damage). High blood pressure affects the blood vessels on the inner surface of the eye in much the same way that it affects blood vessels in the heart or kidneys. Over time, uncontrolled high blood pressure can cause a blood vessel in the eye to burst, bleed, or occlude, leading to blurred vision or even blindness.