Understanding Stroke Causes and Risk Factors

A stroke happens when blood flow to a part of the brain is suddenly cut off. The brain relies on a constant supply of oxygen-rich blood delivered through arteries that carry blood from the heart. If one of the arteries becomes blocked or bursts, blood can’t reach the brain tissue it normally supplies. Without a steady supply of oxygen-rich blood, brain cells will begin to die. Even a short disruption in blood flow can cause lasting damage in the brain.^4,5

Depending on the part of the brain affected, a stroke can affect how you move, speak, or think. That’s why it’s so important to get medical care as soon as possible when a stroke occurs. ^4,5

You may hear doctors refer to a stroke with different names, such as a brain attack or a cerebrovascular accident (also known as the medical abbreviation CVA). These terms all mean the same thing. ^4,5

A stroke happens when blood flow to part of the brain is interrupted, but there are different reasons why people have strokes. There are different types of strokes, each with its own cause. ^4,5

An ischemic stroke is the most common type of stroke. It accounts for about 87% of all strokes. During an ischemic stroke, a blood clot blocks one of the arteries providing blood to the brain. When the brain artery is blocked, it reduces blood flow (called ischemia).^4-6

In some cases, a blood clot forms in a blood vessel inside the brain. This type of stroke is also called cerebral thrombosis or a thrombotic stroke. It’s most commonly caused by atherosclerosis (fatty deposits that build up on the artery wall). ^4-6

In other cases, a blood clot forms in another part of the body, such as the heart. If the blood clot in the heart breaks off, it can travel through the bloodstream to the brain, where it gets stuck in a brain artery, cutting off the supply of oxygen-rich blood. This type of ischemic stroke is called a cerebral embolism or embolic stroke. AFib is the main cause of embolic strokes. ^4-6

A hemorrhagic stroke happens when a blood vessel in the brain bursts and bleeds into the surrounding tissue. The leaking blood builds up in the area and compresses the surrounding brain tissue.^4,5

Factors that can increase the risk of a hemorrhagic stroke include:^5,7

• Uncontrolled high blood pressure, which can weaken blood vessel walls over time
• Blood thinners at high or unsafe levels, which can increase the risk of bleeding
• Bulges at weak spots in the wall of blood vessels in the brain, called aneurysms
• Head injury or trauma, which can cause bleeding in the brain
• Cerebral amyloid angiopathy, which causes protein deposits in the blood vessel wall
• Bleeding after an ischemic stroke
• Arteriovenous malformations (AVM), which is a tangle of abnormal blood vessels that can rupture and bleed

A transient ischemic attack is also known as a mini-stroke or by the medical abbreviation TIA. It happens when blood flow to the brain is temporarily blocked, usually for a few minutes. TIAs are usually caused by the same factors as an ischemic stroke, such as blood clots or atherosclerosis. However, in a TIA, the blood clot dislodges or dissolves on its own, making the effects temporary.^4,5,8

Symptoms of a TIA usually only last a few minutes. However, TIAs are often a warning that a full-blown stroke could happen in the near future. 

A stroke can affect anyone, but some people have a higher risk than others. Most people who have strokes are older than 55 years. Men are more likely to have a stroke than women. However, when women have a stroke, they’re more likely to die than men.^5,7

Your lifestyle habits can play a big role in your risk of stroke. Risk factors for stroke: ^5,7

• Not getting enough physical activity
• Drinking alcohol
• Smoking or using other types of tobacco or vaping
• Using recreational drugs

Several health conditions can also increase the risk of stroke, such as: ^5,7

• Overweight or obesity
• High blood pressure
• High cholesterol
• Diabetes
• Obstructive sleep apnea
• Heart disease, including AFib, heart failure, and heart defects
• Recent or ongoing COVID-19 infection
• Frequent migraine headaches

Your doctor can help you understand which risk factors for stroke you may have.  

AFib is one of the medical conditions that can increase your risk of stroke. In AFib, the atria (the upper chambers of the heart) beat irregularly. This irregular rhythm prevents the heart from efficiently pumping blood out of the heart with each beat.⁹

The blood left behind in the heart can begin to pool, making it easier for blood cells to stick together and form blood clots. Blood clots often form in a small pouch in the atria called the left atrial appendage (LAA). If a blood clot escapes from the LAA, it can travel to the brain and cause an embolic stroke. ⁹

People with AFib are about five times more likely to have a stroke than those with a regular heartbeat.³ Reducing the risk of stroke is one the most important AFib treatments .¹⁰

Your doctor can use an assessment called the CHA₂DS₂-VASc risk to help decide if you need additional treatment to lower your stroke risk. This tool helps to estimate your chances of having a stroke by looking at different risk factors. These include your age, sex, and whether you have certain health conditions.¹¹

Each factor is given a score. Your total will help your doctor decide what kind of stroke prevention you might need.

If your risk of stroke is high, your doctor may recommend treatments to lower your risk. Blood thinner medications can help prevent the formation of blood clots. Taking blood thinners increases your risk of bleeding.¹¹ Learn more about how blood thinners work.

Some people with non-valvular AFib who need an alternative to blood thinners may be eligible for a one-time procedure to close off the LAA, where most stroke-causing blood clots are formed.^12,13 The WATCHMAN Implant is placed in a safe, minimally-invasive one-time procedure to close the LAA and reduce stroke risk – without the need for lifelong blood thinners.¹⁴

There are risks associated with all medical procedures. Please talk with your doctor about the risks and benefits of the WATCHMAN Implant.