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Stroke Causes and Risk Factors

Stroke, sometimes called a ‘brain attack’, is a life-threatening condition that occurs when a blood vessel in the brain is either blocked by a blood clot or ruptured. When this happens, part of the brain can not get the blood (and oxygen) it needs, so the cells begins to die and abilities controlled by the area of the brain, such as memory and muscle control, are lost.

According to the American Stroke Association, stroke is the fifth leading cause of death in the United States and nearly 800,000 people in the United States have a new or recurrent stroke each year.

What Causes a Stroke?

The causes of stroke depend on the type of stroke you have. There are three major types of stroke: ischemic stroke, hemorrhagic stroke, and transient ischemic attack (TIA).

Ischemic stroke

Ischemic stroke is the most common type of stroke, accounting for approximately 80% of all stroke cases. This type of stroke is caused by a blockage of blood flow to areas of the brain. The most common types of ischemic stroke include:

  • Embolic stroke
    Embolic stroke occurs when blood clots or cholesterol plaques travels through bloodstream into the brain. When it enters a blood vessel that’s too small to allow it to pass, the blood clots block the flow of blood to the brain.

    These blockages are called emboli. Emboli can also result from an abnormal heartbeat. This is known as atrial fibrillation. When the heart doesn’t beat effectively, it can cause blood to pool and form clots.

  • Thrombotic stroke
    In this type of Ischemic stroke, blood clots form inside one of the brain’s arteries, causing a blockage of blood flow to a part of the brain. This causes brain cells in that area to stop functioning and die quickly. These strokes tend to cause the most disability.

Hemorrhagic stroke

Hemorrhagic stroke is caused by either a ruptured brain aneurysm or a weakened blood vessel leak. This stroke is less common, which accounts for only 15% of all strokes.

There are two types of hemorrhagic stroke: intracerebral and subarachnoid.

  • Intracerebral hemorrhage (ICH)
    Intracerebral hemorrhage is the most common type of hemorrhagic stroke. It occurs when a blood vessel inside the brain bursts and leaks blood into surrounding brain tissue. The bleeding causes brain cells to die and the affected part of the brain stops working correctly. High blood pressure and aging blood vessels are the most common cause of this type of hemorrhage.
  • Subarachnoid hemorrhage (SAH)
    Subarachnoid hemorrhage is a less common type of hemorrhagic stroke. It is characterized by bleeding in the area between the brain and the tissue covering the brain, known as the subarachnoid space. This type of stroke is most often caused by a burst aneurysm.

Transient ischemic attack (TIA)

A transient ischemic attack, also known as a mini stroke, is caused by a temporary disruption in the blood supply to part of the brain.

The disruption in blood supply results in a lack of oxygen to the brain which cause sudden symptoms similar to a stroke, such as temporary loss of vision, slurred speech and weakness of the face, arm or legs.

However, the symptoms don’t last as long as a stroke. They usually only last for a few minutes or hours and fully resolve within 24 hours. This is why a transient ischemic attack is often referred to as a mini-stroke.

Although a transient ischemic attack does not usually cause permanent damage to the brain, it can be a warning sign that you are likely to have a stroke in the future.

If you think you are having a TIA, call 911 or seek emergency services right away. Early treatment can help prevent a stroke. If you think you have had a TIA but your symptoms have gone away, you still need to call your doctor right away.

What are the Risk Factors for a Stroke?

Many factors can increase your stroke risk. Of these risk factors, some may be controlled or modified like diet and physical activity, while others can’t be controlled like age and family history.

Uncontrollable risk factors

Risk factors that can not be changed or controlled include:


Although stroke affects people of all ages. But the older you are, the greater your stroke risk.


Men are more likely to have stroke than women. However, women are more likely to die from strokes. Women who take birth control pills also are at slightly higher risk of stroke.


African-Americans have a much higher risk of stroke than Caucasians. This is mostly because they have higher risks of high blood pressure, diabetes and obesity. Hispanics and Latinos are also at higher risk of stroke.

Prior Stroke or TIA

If you’ve had a prior stroke, you’re at higher risk for another one. A person who had a TIA is almost 10 times more likely to have a stroke than someone of the same age and sex who hasn’t. Recognizing and preventing TIA can reduce the risk of stroke.

Controllable risk factors

Risk factors that can be changed include:

High blood pressure

High blood pressure is one of the major risk factors for both ischemic and hemorrhagic stroke. Blood pressure is considered high if it is above 140/90 mmHg, reducing it even a small amount can help lower your risk of these conditions.


Smoking increase your stroke risk because it can damage blood vessels. This can lead to blockages within those blood vessels, causing a stroke. Exposure to secondhand smoke also can damage the blood vessels. So, don’t smoke and avoid second-hand smoke.


Diabetes is a condition in which a person’s blood sugar level become too high. Individuals with diabetes are almost twice as likely to have a stroke than individuals of the same gender and age who don’t have diabetes.

High cholesterol

High amounts of cholesterol in the blood can cause fatty deposits to build up in your arteries. This can make the arteries narrowed and stiff, making it harder for blood to flow. When this happens, a stroke can result.


Several studies have found that drinking moderate amounts of alcohol, such as one or two drinks per day, can actually reduce the risk of stroke. However, people who drink heavily are three times more likely to have a stroke, particularly a hemorrhagic stroke.


Certain drugs, such as ecstasy, cocaine, and heroin, have been associated with increased risk of stroke. Some of these drugs directly affect the blood vessels in the brain, causing a stroke.


Being overweight or obese can also increase the risk of stroke. Too much body fat can contribute to high blood pressure, high cholesterol, and may lead to heart disease and type 2 diabetes – all increase your chance of having a stroke.

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