Let's Talk About What Causes a Stroke

On the health-fear meter, strokes are right up there with heart attack. The causes are similar, too.

by Matt McMillen Health Writer

A stroke often occurs out of the blue—and it can be devastating. But as scary as they are, there's actually a lot you can do to help prevent one, and we bet you're already doing some of the things already, like eating nutritious foods, logging time on the treadmill, and managing any other chronic illnesses you may have, like diabetes or heart disease. More good news: The efforts you make to protect your brain from a stroke will strengthen your heart health, too. In fact, your whole body will benefit. So, let’s not wait another moment—read on to learn more about the causes of stroke and how to sidestep them!

Stroke Causes

Our Pro Panel

We went to some of the nation's top experts in stroke to bring you the most up-to-date information possible.

Rohan Arora, M.D.
Rohan Arora, M.D.

Rohan Arora, M.D.

Director, Stroke Program

Long Island Jewish Forest Hills

Queens, NY

Ghulam Abbas Kharal, M.D.
Ghulam Abbas Kharal, M.D.

Ghulam Abbas Kharal, M.D.

Neurologist

The Cleveland Clinic

Cleveland

Vivien Lee, M.D.
Vivien Lee, M.D.

Vivien Lee, M.D.

Medical Director

The Ohio State University Wexner Medical Center’s Comprehensive Stroke Center

Columbus, OH

Stroke Causes
Frequently Asked Questions
What should I do if I think I’m having a stroke?

Don’t hesitate: Call 911. There’s a saying: Time is brain. That means the faster you get care, the less damage your brain will suffer and the better your outcome. In fact, early treatment may be able to reverse the damage that’s been done. But remember: Strokes can be fatal, and they can also cause permanent disability. So get to a hospital—stat.

How do I know if I or someone I’m with is having a stroke?

Here’s a quick acronym that will help you remember the most common symptoms: FAST. “F” stands for facial drooping due to paralysis, often on one side only. “A” stands for arm weakness. (When you lift both arms, one will drift back down.) “S” stands for speech, which often becomes slurred during a stroke, difficult to understand, or even impossible to do. “T” stands for time—meaning, it’s time to call 911.

Are all strokes equally dangerous?

Strokes vary in severity, but they are always medical emergencies. Even mini-strokes, otherwise known as transient ischemic attacks (TIA), need to be addressed immediately. Though it causes no permanent damage and lasts only a little while, a TIA sends a clear message: Your risk for a real stroke is quite high.

Will I need a caregiver after my stroke?

That will depend on the disability that your stroke has caused. If you do need a caregiver to help you with the basic tasks of daily living, like getting dressed and eating, it may be temporary until you’ve progressed through rehab and are once again able to care for yourself.

What Is a Stroke, Anyway?

Like the rest of your body, your brain needs oxygen to survive and thrive. It gets that oxygen from the blood flowing from your heart through a network of arteries. A stroke happens when the blood supply slows to a trickle or gets cut off completely. Your brain cells become starved of oxygen, and they quickly die.

Because your brain controls pretty much everything your body does, the death of those brain cells can have severe downstream effects. For example, if an artery gets blocked and can no longer deliver blood to the part of your brain that helps manage how well you move, the resulting stroke can cause permanent balance and other mobility issues.

In fact, stroke is a leading cause of adult disability in the U.S., according to the Centers for Disease Control and Prevention (CDC). It’s also the fifth-leading cause of death. Nearly 800,000 people have a stroke each year in this country; 140,000 of those strokes are fatal.

If this sounds distressing, it certainly is. But here’s the thing: Four out of five strokes are preventable, according to the American Stroke Association. By better managing certain health conditions—like diabetes or atrial fibrillation—and by making healthier choices about what you eat and drink, how you sleep, and how much you move, you up your odds of never having one.

What Are the Types of Stroke?

There are two major types of stroke: ischemic stroke and hemorrhagic stroke. Ischemic strokes occur far more often—they account for more than four out of five strokes. Let’s get into the details of both:

Ischemic Stroke

If you’ve read up on heart attacks, you’ll likely notice some similarities here. You may even see stroke referred to as a “brain attack.” The reason: Both are the result of blocked arteries. During an ischemic stroke, a blockage stops blood from flowing into or through parts of the brain.

You may have also heard of “mini-strokes,” or TIAs (transient ischemic attack), which can temporarily cause stroke symptoms. They, too, are caused by blockages from narrowed or clogged arteries, but these blockages are brief and aren’t permanent, so symptoms don’t last. However, TIAs are a medical emergency and should be treated as such because they are often a sign a real stroke is about to happen.

In addition, there are "silent strokes," so called because they often exhibit no (or few) obvious symptoms. However, this type of stroke can do permanent damage to your brain over time. Like all strokes, a silent stroke occurs when part of your brain’s oxygen supply gets cut off, but it doesn’t tend to affect brain regions that control speech and movement (which is why you might not know you've had one). Instead, a silent stroke damages areas responsible for executive function—your ability to do things like plan, concentrate, and problem-solve, as well as manage your emotions, so outward signs may be subtle. What's more, clots may not be the only culprit behind silent strokes. People with atrial fibrillation may also have blood vessels that don't work properly, which can cause inflammation in the brain, upping risk for silent stroke. This type of stroke is often only detected when your doctor spots tell-tale damage on the brain during an MRI scan.

Hemorrhagic Stroke

The less-common stroke is also a very dangerous one: Half of those who have a hemorrhagic stroke never make a full recovery. They occur when an artery ruptures. Think of your arteries like hoses through which your blood flows. If one bursts or breaks, blood goes everywhere except where it’s meant to go. This is bad news for two reasons: Your brain loses oxygen, and the bleeding itself increases pressure, which further damages surrounding tissue. Such ruptures can be triggered by a traumatic head injury, but to be considered a stroke, the ruptured artery must happen spontaneously, most often due to high blood pressure (HBP).

There are two main types of hemorrhagic stroke:

  • Subarachnoid. These occur when an artery bursts near the surface of your brain and spills blood into the space just inside your skull.

  • Intracerebral. These strokes occur deeper inside your brain.

What Causes a Stroke?

The simple answer: A stroke is caused by the sudden drop in blood supply to the brain. But what leads to this event? Often, it’s damage to the heart and your arteries that builds up over many years. There’s a long list of risk factors for stroke, some that you can address and a few that you can’t. Still, there’s much you can do to prevent a stroke from happening. Here’s how.

What Are the Risk Factors for Stroke That I Can Control?

Turns out, there are loads! And the beautiful thing is that when you improve one area, you often simultaneously help another—without any extra effort.

High Blood Pressure (HBP, a.k.a. Hypertension)

This is the most common cause of ischemic stroke. When your heart beats, it pumps blood through your arteries. The force with which your blood presses against the walls of your arteries is your blood pressure.

Your blood pressure has two parts: systolic and diastolic.

  • Systolic indicates your blood pressure when your heart beats.

  • Diastolic is a measure of your BP between beats.

When you see it written out, the systolic sits on top of the diastolic, for example, 120/80. A normal blood pressure is at or below that threshold.

Your blood pressure rises and falls throughout the day, and it can spike temporarily due to things like stress. That’s normal. However, when your blood pressure stays above normal continuously, you have a problem. Here's a breakdown about why:

  1. High blood pressure makes your heart work harder than it should, which can damage it over time. HBP also stiffens and thickens your arteries, so that they become narrower.

  2. When that happens, blood cannot flow through them as easily as it should.

  3. Slow-moving blood tends to clot, and clots can travel from arteries throughout the body to the brain, where they block an artery and trigger an ischemic stroke. Most such clots can be traced back to arteries in the heart.

  4. HBP can also cause hemorrhagic stroke. The longer your blood pressure remains elevated, the weaker the walls of your arteries become, until one in your brain eventually bursts.

  5. HBP also leads to aneurysms, a section of blood vessel that balloons out from the artery’s wall. Such aneurysms can form in the brain; they’re called cerebral aneurysms, and they’re prone to bursting, which can be a life-threatening event.

Atherosclerosis

This slow moving condition can start as early as childhood. It’s not clear what causes it, but a lot of factors related to stroke are involved, including HBP and others we’ll get to shortly, like smoking and high cholesterol. When you have atherosclerosis, a fatty substance called plaque builds up on the walls of your heart’s network of arteries. Over time, that buildup makes it harder and harder for blood to flow freely through your arteries. Clots can form as a result, and one of those clots can journey to the brain and block an artery there. The plaque formations also can rupture, or break apart, and that, too, can lead to clots with the potential to cause a stroke.

Previous Heart Attack

If you’ve had a heart attack, your heart may have been damaged in such a way that it can’t pump blood as well as it once did. That increases the likelihood that you’ll develop a blood clot.

Diabetes

When it’s poorly managed, diabetes causes your blood sugar level to rise. This can set off a whole cascade of dangers: The excess sugar damages your blood vessels and contributes to heart diseases like coronary artery disease and heart failure, both of which can cause clots that lead to stroke. People with diabetes also tend to have other stroke risk factors, HBP chief among them, but also obesity, lack of exercise, and poor diet.

Atrial Fibrillation

When your heart beats too fast, too slow, or erratically, you have what’s called an arrhythmia. Afib is the most common type of arrhythmia, and it’s one of the leading causes of stroke. Why? It prevents your heart from pumping out as much blood as it should. The blood that remains in the heart can pool and clot in the heart’s upper chambers, or atria, boosting your risk of clots traveling to your brain, blocking blood flow. What's more, people with afib also have a higher risk of "silent stroke," whose symptoms are subtler than a regular ischemic stroke. A silent stroke may be caused by clots or improperly working blood vessels that can lead to inflammation in the brain's arteries.

Obstructive Sleep Apnea (OSA)

OSA stops your breathing very briefly but often very frequently throughout the night. You may not realize it’s happening, but you’ll feel it during the day when you’re sluggish from lack of good sleep. Behind the scenes, though, worse things are happening. OSA elevates your blood pressure and makes it harder to treat. Sleep apnea also ups your chances of afib.

High Cholesterol

There’s nothing wrong with cholesterol—you need some to live, and your liver actually produces it. But when there’s too much of it in your bloodstream, due to diet, lack of exercise, or to a medical condition like hypercholesterolemia, for example, it can cause problems. In fact, it’s one of the main ingredients in the plaque that can build up on the walls of your arteries from atherosclerosis. Your doctor will distinguish between “good” cholesterol, called high density lipoprotein (HDL) cholesterol, and “bad” cholesterol, or low density lipoprotein. Your cholesterol is considered high when your total cholesterol has too much of the bad and too little of the good.

Smoking

We know you know that there are many, many reasons to quit smoking. It causes lung cancer, of course, but it also does a lot of harm to your blood vessels. It’s a key culprit in the buildup of dangerous plaques that occurs due to atherosclerosis. It boosts your bad cholesterol and your triglycerides, another type of fat that circulates in your bloodstream that has been linked to ischemic stroke. Smoking also makes your blood sticky and prone to clots.

And don’t forget: You don’t put only yourself at risk when you smoke. Secondhand smoke causes 8,000 stroke deaths every year, according to the CDC. While there’s less known about the dangers of vaping, many of the same toxic chemicals in tobacco smoke also can be found in e-cigarette ‘smoke.’ To get help quitting smoking, visit the American Heart Association online support page.

Lack of Exercise

Just like quitting smoking, working up a sweat—at the gym, in the pool, on that treadmill or stationary bike in your basement—will protect your heart and brain. Here's how:

  • Lower blood pressure because a fit heart beats more efficiently

  • Higher levels of good cholesterol, which helps rid your body of bad cholesterol

  • Weight loss

  • Stress reduction due to lower levels of stress hormones like adrenaline and cortisol

  • Better diabetes management

Experts recommend at least 150 minutes a week of moderate exercise—that might mean a brisk walk with a friend every other day. You may also benefit from adding weightlifting to your routine. If you’re not sure how well your body will handle a workout, check in with your doctor before you get started.

Obesity

Excess weight makes your heart’s job harder because it has to pump more blood in order to meet your body’s demands for oxygen. That can bump up your blood pressure. And, because that extra work can cause your heart to enlarge and stiffen, it gets you closer to heart-failure territory, another risk factor for stroke. Obesity also plays a role in sleep apnea, diabetes, and atrial fibrillation. Do you have a lot of fat in your midsection? That’s a concern because abdominal fat has been linked to strokes. If you’re not sure where, exactly, you fall on the scale, try our DIY weight calculators to determine whether your weight is in a healthy range.

Poor Diet

This goes hand in hand with many other stroke risk factors, like obesity, high cholesterol, diabetes, and lack of exercise. Here are some foods to add to your least-wanted list:

  • Foods high in saturated fats, like beef and butter. (Lean meats, fish, and olive oil are better choices.)

  • Foods with trans fats, such as those found in some store-bought cookies, cakes, crackers, margarine, and potato chips

  • Foods with lots of cholesterol, like bacon, cheese, butter, and fatty meats

  • Foods with a large amount of sodium, including processed meats, pizza, lots of canned foods, like soup and chili, and snack foods

Avoiding or significantly limiting these types of foods should help keep your blood pressure down, your waistline trim, and your cholesterol level in a healthy range. What should you eat instead? No one diet works for everyone, but your focus should be on fruits, vegetables, whole grains, legumes like beans, lean meat and fish, and nuts.

Excess Alcohol

Many people love to unwind with a drink, and to that we say, “Cheers!” But overdoing it can raise your blood pressure and cholesterol and expand your waistline. Alcohol can also trigger atrial fibrillation. If you’re a man, limit yourself to two drinks a day. Women should drink no more than one drink. A drink equals 12 ounces of beer, five ounces of wine, or 1.5 ounces of liquor, such as rum, scotch, or vodka.

Illegal Drugs

Drugs like cocaine and amphetamines can cause your arteries to spasm, which in turn can cause them to narrow. If they remain narrowed long enough, a stroke can result.

What Are the Risk Factors for Stroke That I Can’t Control?

The above risk factors can modified, managed, or even quit forever, all (or any) of which helps protect you from a stroke. But you’re stuck with a few risk factors—thankfully, not many!—that simply come with being alive. They include:

Previous Stroke

It hardly seems fair, to have survived a stroke and then perhaps face one again. But approximately 25% of people who’ve already had a stroke will have a second one, too.

Age

The older you get, the more likely a stroke becomes. In fact, about 75% of strokes occur in people over age 65. Why? One big reason: The older we get, the more likely we are to have conditions that lead to a stroke, such as HBP, diabetes, afib, and heart disease.

Family History

You may have inherited genes that raise your blood pressure or cholesterol out of the healthy range. And if you have a sibling who had a stroke before turning 65, your own risk of having one may increase by up to 60%, according to the AHA.

Race

African Americans and Hispanic Americans have a higher risk of strokes than whites, and their strokes are more likely to be fatal. African Americans also have higher rates of sickle cell anemia, which contributes to stroke risk. Healthcare disparities in these communities (which can lead to more underlying health conditions like HBP that up the risk for stroke) may play a role, too.

Now that you know the causes of stroke, you can take the steps now to help prevent one from happening down the line. Manage chronic health conditions like HBP, atrial fibrillation, and diabetes, quit smoking, lose weight, eat well and move your body more, get quality sleep, and don’t overdo the drinking. Not only your brain thank you for your efforts, your heart will, too.

Matt McMillen
Meet Our Writer
Matt McMillen

Matt McMillen has been a freelance health reporter since 2002. In that time he’s written about everything from acupuncture to the Zika virus. He covers breaking medical news and the latest medical studies, profiles celebrities, and crafts easy to digest overviews of medical conditions. His work has appeared, both online and in print, in The Washington Post, WebMD Magazine, Diabetes Forecast, AARP, and elsewhere.