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Blood Pressure: Your Questions Answered

BY Lisa Fields February 8, 2024

Yale Medicine experts discuss the effects of hypertension on the body.

Your doctor takes your blood pressure whenever you have an appointment because it’s a quick, simple way for physicians to gauge your cardiovascular health. But fewer than half of patients know the upper limits of healthy blood pressure levels, even if they think they do, according to a 2023 study published in Medical Decision Making.

“Blood pressure is an extremely affordable and safe way to provide insight into the functioning of the heart and its blood vessels,” says Yale Medicine cardiologist Ehimen Aneni, MD, MPH. "Everyone should understand how blood pressure works and how it can affect their body."

Blood pressure can be high—even dangerously so—without causing symptoms, which is why regular checks are necessary. High blood pressure, or hypertension, may lead to serious heart-related issues, such as a heart attack or stroke.

“People don’t feel symptoms of hypertension because their body adjusts gradually to the change in blood pressure,” says Yale Medicine cardiologist Antonio Giaimo, MD. “But that adjustment shouldn’t be misinterpreted as ‘everything’s okay.’”

A blood pressure check measures the pressure that blood exerts while it pushes against the artery walls when the heart beats and also between heartbeats. A reading contains two numbers: systolic pressure, or the top number, and diastolic pressure, or the bottom number.

  • The systolic pressure is measured when the heart beats, contracting to push blood out of the heart.
  • The diastolic pressure is measured between heartbeats, when the heart relaxes, opening to fill up with more blood.

Blood pushed out of the heart enters the aorta, the main artery that carries blood from the heart to the rest of the body. “The aorta branches out to smaller blood vessels in the same way that a major highway branches out to smaller roads,” Dr. Aneni says. “We measure blood pressure on one of the smaller blood vessels.”

Below, Drs. Aneni and Giaimo answer other common questions about blood pressure and the effects of hypertension on the body.

What is blood pressure, and how is it measured?

Blood pressure measures the force your heart uses to pump blood around your body.

At home or in a pharmacy, blood pressure is typically measured electronically. You place your arm in a cuff, which automatically contracts for a few seconds to stop the blood from flowing through the artery. When the cuff loosens, the monitor measures when the blood starts flowing again—first, the systolic pressure, then the diastolic pressure.

What do the numbers in blood pressure readings mean?

The systolic and diastolic numbers can show whether a person has normal, elevated, or high blood pressure levels.

  • In people with normal blood pressure, the systolic pressure is below 120 mm Hg, and the diastolic pressure is below 80 mm Hg.
  • In people with elevated blood pressure, the systolic pressure is between 120 and 129 mm Hg, and the diastolic pressure is below 80 mm Hg.
  • In people with stage 1 hypertension, the systolic pressure is between 130 and 139 mm Hg, or the diastolic pressure is between 80 and 89 mm Hg.
  • In people with stage 2 hypertension, the systolic pressure is 140 mm Hg or higher, or the diastolic pressure is 90 mm Hg or higher.
  • When a person is having a hypertensive crisis, which is a medical emergency, the systolic pressure is higher than 180 mm Hg, and/or the diastolic pressure is higher than 120 mm Hg.

People with elevated blood pressure are advised to make healthy lifestyle changes to lower their numbers. Those with high blood pressure are also advised to watch their diet, exercise regularly, and manage stress, and they may be prescribed medication (more on that below).

“There’s some nuance as to when we treat with medication,” Dr. Aneni says, “but at 140/90 mm Hg, for example, everybody gets treated.”

Is ‘white coat hypertension’ a myth?

White coat hypertension—when a patient’s blood pressure levels are higher than usual in a doctor’s office, usually due to anxiety—happens to about 15% of people.

When physicians expect a patient to have normal blood pressure levels but their numbers are high, they may recheck their blood pressure in one of two ways:

  • Patients can check their blood pressure at home. “Blood pressure kits are now quite inexpensive,” Dr. Aneni says. “Insurance may cover the blood pressure kit, too.” Look for a monitor with a cuff that goes around the upper arm; wrist monitors are more likely to give false readings.
  • Doctors may give patients a wearable 24-hour ambulatory blood pressure monitor, which checks blood pressure every 20 to 30 minutes. “It’s the gold standard for finding out whether you have white coat hypertension,” Dr. Giaimo says.

How does high blood pressure affect the body?

High blood pressure causes blood vessels to lose their elasticity, lessening their ability to expand and contract normally and damaging the artery walls. What’s more, cholesterol plaque (fatty deposits) is more likely to build up on the inner walls of these blood vessels. That’s because plaque-forming cholesterol is more likely to attach to small tears in artery walls (part of the damage caused by hypertension), making them even narrower. This causes blood pressure to rise even more.

“When high blood pressure is not controlled, the heart has to do more work in order to pump out adequate blood,” Dr. Aneni says. “This may cause the heart muscle to become thicker and bigger, experiencing abnormal function, which we call heart failure.”

Hypertension is also a major risk factor for heart attack, stroke, transient ischemic attack (TIA, sometimes called a mini-stroke), atrial fibrillation and other heart rhythm disorders, peripheral artery disease (narrowing of arteries in the arms or legs), hypertensive retinopathy (damage to the eye’s retina, caused by high blood pressure), and chronic kidney disease.

How is high blood pressure treated?

Health care providers recommend lifestyle changes to patients with elevated or high blood pressure levels. These changes may eliminate the need for medication.

However, for some people, including those with a family history of high blood pressure, lifestyle changes may not be effective on their own, so they may be prescribed medication.

Healthy lifestyle habits that can help lower blood pressure include:

  • Adopting a healthy eating style. The Dietary Approaches to Stop Hypertension (DASH) diet can reduce your salt intake. (Too much salt in your diet makes the heart pump harder, and it narrows the arteries over time.) This eating plan focuses on fruits, vegetables, whole grains, nuts, beans, low-fat or fat-free dairy, fish, and poultry. People should avoid red meat, processed foods, sweetened beverages, sugary snacks, and salt-containing foods.
  • Being more physically active. Strive for 30 minutes of moderate-intensity exercise daily or 75 minutes of high-intensity exercise weekly. Brisk walking is an example of a moderate-intensity exercise. Singles tennis is a high-intensity exercise.
  • Maintain a healthy weight. Losing weight if you’re overweight has been shown to help lower blood pressure levels, because your heart does not have to work as hard.
  • Avoiding or limiting certain habits. People who smoke should quit, because nicotine increases blood pressure levels and contributes to damage of the blood vessels. It’s also important to limit your alcohol intake, because drinking may contribute to high blood pressure by narrowing the blood vessels.
  • Managing stress levels. Anxiety caused by stress makes your blood pressure rise temporarily. Find ways to reduce your stress load, such as lightening your schedule, so you don’t feel pressured to be productive every moment. Or, say no to unnecessary responsibilities.

“If a person is able to be active, eat right, and lose some weight, the reduction in the blood pressure is quite significant,” Dr. Aneni says.

If a patient’s blood pressure is 140/90 mm Hg or higher, or if they can’t lower their blood pressure with lifestyle changes, doctors typically prescribe medication. Many types are available, including angiotensin-converting enzyme (ACE) inhibitors, which help the blood vessels to relax, thereby lowering blood pressure, and calcium channel blockers, which affect the way that calcium moves into and out of the cells of the blood vessels, causing them to relax, thereby lowering blood pressure.

How can you prevent high blood pressure?

The same lifestyle changes that are recommended to patients with hypertension may decrease your risk of developing the problem: eating a healthy diet, exercising regularly, maintaining a healthy weight, avoiding smoking, minimizing drinking, and managing stress levels.

“Many people who have genetic risk factors for high blood pressure can delay its onset by adhering to a healthy lifestyle,” Dr. Aneni says. “Even for those with a non-genetic risk, modifying lifestyle habits helps a great deal.”

Learning your numbers early may also inspire you to adopt lifestyle habits to decrease your risk, the doctors say.

“When some patients find out their blood pressure is a little high, they put it to the side, but I’d encourage them to address it head-on,” Dr. Giaimo says. “The longer you avoid addressing it, the more difficult it is to address. It may save you from needing medication in the future.”