When your doctor takes your blood pressure, they’re measuring the amount of pressure that’s generated inside your arteries with each heartbeat. This measurement generates two numbers — a systolic blood pressure and a diastolic blood pressure.

When these numbers are higher than normal, you’re said to have high blood pressure, which can put you at risk for things like heart attack and stroke.

But what if your systolic blood pressure is high and your diastolic blood pressure is normal?

This is referred to as isolated systolic hypertension (ISH) and should be a cause for concern. This is because, like other types of high blood pressure, ISH can also contribute to the risk of heart attack and stroke. It can also be an indicator of other conditions such as anemia and hyperthyroidism.

ISH is the most common type of high blood pressure in people older than 65, according to Mayo Clinic. Additionally, according to the American College of Cardiology, ISH can increase the risk of heart disease and death in young adults.

Blood pressure involves both how much blood your heart pumps every minute as well as the pressure exerted on the walls of your arteries by that blood.

As you age, your arteries lose some of their natural elasticity and are less able to accommodate the rush of blood. Plaques, which are fatty deposits on the artery wall, can also contribute to stiffening of the arteries.

Blood pressure — particularly systolic blood pressure — naturally tends to increase with age. Because of this, there may be no identifiable cause for high blood pressure.

However, there are some medical conditions that can cause someone to develop ISH. These conditions often have effects on the circulatory system, which can damage blood vessels or contribute to artery stiffening. Some of these conditions include:

Anemia

Anemia occurs when you don’t have enough red blood cells to carry oxygen to your tissues or when your red blood cells aren’t functioning properly. There are many types of anemia, but iron deficiency anemia is the most common.

Damage can be caused to your blood vessels as your heart works harder to pump blood to the tissues of your body in order to deliver sufficient oxygen.

Diabetes

Diabetes happens when the amount of glucose in your blood is too high. Insulin normally controls blood glucose levels. In diabetes, your body either doesn’t produce insulin (type 1 diabetes) or uses insulin poorly (type 2 diabetes).

Over time, high glucose levels in your blood can lead to a variety of problems, including those with the heart and circulatory system.

Hyperthyroidism

Hyperthyroidism, or overactive thyroid, occurs when your thyroid gland produces more thyroid hormones than necessary. This surplus of thyroid hormone can affect almost every organ in your body, including your heart and circulatory system.

Obstructive sleep apnea

Obstructive sleep apnea is when muscles in your throat relax and block your airway while you’re sleeping, causing your breathing to stop and start again. Because blood oxygen levels can drop when breathing stops, obstructive sleep apnea can strain your cardiovascular system and lead to increases in blood pressure.

When high blood pressure is left uncontrolled, it can cause damage to your arteries. This can affect various parts of your body and can increase your risk for the following conditions:

A blood pressure reading consists of two numbers — your systolic blood pressure and your diastolic blood pressure. But what do these numbers actually mean?

The first number is your systolic blood pressure. It’s a measurement of the amount of pressure placed on the walls of your arteries when your heart beats.

The second number is your diastolic blood pressure. It’s a measurement of the pressure on the walls of your arteries between heartbeats.

Understanding readings

Blood pressure is measured in millimeters of mercury (mm Hg).

There are several different blood pressure categories, which are currently defined as the following:

NormalSystolic less than 120 mm Hg AND diastolic less than 80 mm Hg
ElevatedSystolic between 120–129 mm Hg AND diastolic less than 80 mm Hg
Hypertension Stage 1Systolic between 130–139 mm Hg OR diastolic between 80–89 mm Hg
Hypertension Stage 2Systolic of 140 mm Hg or higher OR diastolic of 90 mm Hg or higher
Hypertensive crisis (a medical emergency)Systolic of higher than 180 mm Hg AND/OR diastolic higher than 120 mm Hg

ISH is when you have a systolic blood pressure reading of 140 mm Hg or higher, and a diastolic blood pressure reading of less than 90 mm Hg.

ISH can be treated like other forms of hypertension. The goal is to reduce your systolic blood pressure to below 140 mm Hg. This can be accomplished through implementation of lifestyle changes, through medication, or both.

It’s important that treatment is balanced to achieve a lower systolic blood pressure, but not reduce the diastolic blood pressure too much. Lower-than-normal diastolic blood pressure may lead to heart damage.

If there’s an underlying condition that’s causing or contributing to your ISH, your doctor will work to treat that as well.

Medications

A review of studies in elderly adults with ISH has found that the following medications had the greatest efficacy in reducing risk of stroke and other cardiovascular events.

  • Calcium channel blockers. Calcium channel blockers help the walls to relax by blocking the pathway that causes blood vessel constriction.
  • Thiazide-like diuretics. Thiazide-like diuretics reduce blood volume by helping your kidneys void more sodium and water.

The following drugs were found to have less efficacy, however they may still be effective in treating ISH.

  • Angiotensin-converting enzyme (ACE) inhibitors. ACE inhibitors block the formation of a specific enzyme that leads to narrowing of blood vessels.
  • Angiotensin receptor blockers (ARBs). ARBs block the action of a specific enzyme that can lead to blood vessel narrowing.

Lifestyle changes

You may also need to make some lifestyle changes as part of your ISH treatment plan. These can include:

  • Losing weight. This can help lower your blood pressure. In fact, for every two pounds you lose, you could lower your blood pressure by about 1 mm Hg.
  • Eating a heart-healthy diet. You should also aim to reduce the amount of sodium in your diet. Consider the DASH diet, which emphasizes eating:
    • vegetables
    • whole grains
    • low-fat dairy products
    • fruits
  • Exercising. Not only can exercise help you lower your blood pressure, but it can help you control your weight and stress levels. Aim to perform some sort of aerobic exercise for at least 30 minutes most days of the week.
  • Decreasing alcohol consumption. Healthy alcohol intake is one drink per day for women and two per day for men.
  • Quitting smoking. Smoking can raise your blood pressure and also contribute to a variety of other health problems.
  • Managing stress. Stress can raise your blood pressure, so finding ways to relieve it are important. Examples of techniques to help lower stress are meditation and deep breathing exercises.

You can help to prevent high blood pressure by practicing all of the lifestyle changes mentioned above.

Additionally, you should work with your doctor to carefully manage any preexisting health conditions that can contribute to high blood pressure, such as diabetes.

You can also monitor your blood pressure at home if you’d like to keep a closer eye on changes in your blood pressure outside of your routine checkups.

The symptoms of high blood pressure are typically silent. Many people may not find out they have high blood pressure until they visit their doctor for a routine physical.

There are many home blood pressure monitors available so that you can monitor your blood pressure at home. Some people that should consider doing this include:

  • those with a family history of high blood pressure
  • people who are overweight or obese
  • smokers
  • women who are pregnant

You should always keep a log of your readings. It’s important to note that home blood pressure monitoring isn’t a substitute for a doctor’s visit. If you find that your readings are consistently high, you should make an appointment with your doctor to discuss them.

Isolated systolic hypertension is when your systolic blood pressure is high, but your diastolic blood pressure is normal. It can occur naturally with age or can be caused by a variety of health conditions including anemia and diabetes.

ISH should still be treated even though your diastolic pressure is normal. This is because untreated high blood pressure, including ISH, can lead to a risk of things like heart attack and stroke.

Be sure to have regular physical checkups with your doctor during which your blood pressure is taken. If you have high blood pressure, your doctor will work with you to develop a plan to manage it.