Ask the doctor
A. This question comes up often, perhaps because doctors and patients alike tend to pay more attention to the top (first) number, known as systolic pressure. It reflects the amount of pressure inside the arteries as the heart contracts. The bottom (second) number, diastolic pressure, is always lower since it reflects the pressure inside the arteries during the resting phase between heartbeats.
As it turns out, both systolic and diastolic blood pressure are important. Per the most recent guidelines, you have what's called elevated blood pressure if your systolic blood pressure reading is 120 to 129 mm Hg (which stands for millimeters of mercury). Once your systolic reading reaches 130 or higher or your diastolic reading is 80 or higher, you're considered to have high blood pressure, or hypertension.
Most people have what's known as essential or primary hypertension, which means it's not caused by a medical condition, medication, or substance. Primary hypertension can affect both systolic and diastolic pressure to a similar degree. But sometimes, especially in older people, it affects mainly the systolic pressure; this is called isolated systolic hypertension.
Why does this happen? As you age, your arteries tend to become less elastic and less able to accommodate surges of blood. Blood flowing through your arteries at high pressure can damage the inner lining of these vessels, accelerating the buildup of cholesterol-laden plaque. This further stiffens and narrows the arteries, a condition known as atherosclerosis. Because the same volume of blood has to pass through a smaller area, the systolic pressure tends to rise, while the diastolic pressure remains the same or gradually falls over time. In some people with isolated systolic hypertension, the diastolic pressure reading may drop into the 50s or even the 40s.
Most studies show a greater risk of cardiovascular disease (especially strokes) related to high systolic pressure as opposed to elevated diastolic pressure. But in 2019, an eight-year-long study involving more than 1.3 million adults found that while elevated systolic pressure had a greater effect on cardiac outcomes, high diastolic readings also affected a person's risk, regardless of the systolic reading.
To ensure accurate readings when you're checking your blood pressure at home, be sure to sit comfortably with your back supported, your feet flat on the floor, and your arm resting on a table with your palm facing up. If needed, support your arm with a pillow so that your elbow is at the level of your heart.
— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter
Image: © Vadim Zhakupov/Getty Images
When your doctor takes your blood pressure, they’ll tell you two numbers: They’ll say the numbers as systolic pressure “over” diastolic pressure. For example, a healthy reading is below 120 over less than 80. If
your systolic blood pressure is higher than 130 but your diastolic blood pressure is under 80, that’s called isolated systolic hypertension. It’s the most common kind of high blood pressure in older people. You
probably won’t know you have it unless your doctor tells you -- there usually aren’t any noticeable signs of it until it causes serious health issues. That’s why high blood pressure is sometimes called “the silent killer.” All types of
high blood pressure, including isolated systolic hypertension, can slowly damage the inside of your arteries and cause tiny tears in their walls. A chemical called LDL cholesterol can build up in those
damaged blood vessels and form a layer called plaque. That makes your arteries narrower and raises your blood pressure even higher. When that happens, the arteries that carry oxygen to your heart can get blocked, and that can lead to a
heart attack or a stroke (when blood flow is limited or cut off to part of your brain). It also can make blood vessels in your
brain burst, and that can cause a stroke, too. In other parts of your body, it can strain the blood vessels in your eyes and make
you lose your eyesight or damage the arteries around your kidneys so they don’t filter your blood the way they should. Older people are more likely to have it,
because systolic blood pressure usually goes up as you age.What Problems Can It Cause?
Who Gets Isolated Systolic Hypertension?
- More than 30% of women over 65 and more than 20% of men have this condition.
- If your parents had high blood pressure, you may be more likely to have it.
- African-Americans are more likely than other groups to have high blood pressure.
How Is It Treated?
If your systolic blood pressure is too high, your doctor may prescribe medicine to help bring it down. Drugs used to control blood pressure include:
- Diuretics (water pills) to help your kidneys flush water and sodium from your body
- Beta-blockers to make your heart beat slower and less forcefully
- Angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), or calcium channel blockers to relax your blood vessels
- Renin inhibitors to keep your kidneys from making a chemical that can lead to higher blood pressure
Your doctor also may recommend you do a few other things:
- If you smoke, stop. There are lots of good reasons for this, but nicotine in cigarette smoke can raise your blood pressure.
- Lower the amount of salt in your diet.
- Cut back on alcohol if you drink.
- Get to or stay at a healthy weight.
- Exercise regularly.