How Atherosclerosis Causes Half of All Strokes

Medically Reviewed by David Zelman, MD on June 15, 2021

Having a stroke is one of the most frightening prospects of aging. Strokes can come on suddenly, stealing the use of an arm or the ability to speak. A stroke can be fatal or leave us permanently disabled.

About half of all strokes are caused by atherosclerosis -- the same process of narrowing and hardening of the arteries that causes heart attacks. Atherosclerosis progresses silently, without symptoms, putting our brains and our independence at risk.

Reducing the risk factors for atherosclerosis lowers the risk of stroke. Making a few lifestyle changes can protect your brain from this common cause of strokes.

Facts About Atherosclerosis and Stroke

  • About 700,000 strokes occur each year in the U.S.
  • One in five people will have a stroke in their lifetime.
  • One-quarter of strokes are fatal.
  • Stroke is the third-leading cause of death in the U.S., behind heart disease and cancer.

Although most strokes are survivable, most people never recover completely after a stroke. Around a quarter of those who survive are permanently disabled.

There are two main types of strokes:

Ischemic: An artery inside or leading to the brain becomes completely blocked. Usually this is caused by a blood clot that forms in a clogged artery. It can also be due to a blood clot traveling to the brain from the heart.

Most strokes (about 87%) are ischemic, and most of those are caused by atherosclerosis.

Hemorrhagic: These strokes are caused by bleeding into the brain. Most commonly, high blood pressure causes a small artery to burst open. Abnormal blood vessels (such as aneurysms and arteriovenous malformations) are particularly likely to rupture. The bleeding disrupts healthy blood flow to brain tissue.

Hemorrhagic strokes are less common, making up about 13% of all strokes.

Regardless of whether a stroke is caused by atherosclerosis or bleeding, the symptoms are the same:

  • Sudden weakness on one side (in the face, arm, or leg)
  • Slurred speech or inability to remember words
  • Sudden blurry or double vision

Within hours of a stroke's onset, brain tissue dies from lack of oxygen and nutrients, leaving permanent damage.

If stroke-like symptoms strike, the time to call for help is now. Only prompt medical attention can help prevent permanent damage from a stroke.

With these sobering facts in mind, it's worthwhile to understand the process by which atherosclerosis causes strokes.

How Atherosclerosis Happens

Atherosclerosis occurs in the arteries of the brain the same way it does elsewhere in the body:

  • The inner layer of arteries (the endothelium) is damaged by high cholesterol, smoking, or high blood pressure.
  • Damaged endothelium allows LDL ("bad") cholesterol to enter the artery wall, where it accumulates.
  • The body sends a "clean-up crew" of white blood cells and other cells to the artery, to digest the LDL.
  • Over years, ongoing cholesterol buildup -- and the response to it -- creates a bump on the artery wall called a plaque.

Most commonly, the plaque grows slowly, never causing a problem. In fact, most are never discovered. The arteries in the brain adjust to the slow narrowing, and no symptoms occur.

However, for unclear reasons, plaques can also become inflamed and unstable. If a plaque ruptures, the dangerous material in its center is exposed to blood flowing by. As a result, a blood clot forms, which can rapidly block the artery. The brain tissue downstream is starved for blood and nutrients, and dies within hours.

Risk Factors for Atherosclerosis and Stroke

As a cause of strokes, heart attacks, or other diseases, atherosclerosis has the same risk factors. Get to know them:

The best way to prevent a stroke is to control these risk factors. If you've already had a stroke or other form of atherosclerosis, reducing your risk is even more important.

Atherosclerosis, Strokes, and 'Clot-Busters'

Most strokes are caused by a sudden blood clot -- which itself is caused by atherosclerosis. If given quickly, "clot-busting" drugs can actually reverse some strokes.

The clot-buster (called tissue plasminogen activator, or tPA) must be given within three hours of the first symptoms of stroke to be most effective. It can be given up to six hours after the stroke if administered directly into the blockage area. This procedure is done primarily at bigger hospitals. Unfortunately, most people don't make it to the hospital quickly enough after experiencing symptoms, and tPA is underused.

If you have any symptoms of stroke, don't hesitate: call 911 immediately. It's your best chance at a good outcome from stroke.

Start reducing your risk factors for stroke today, and you'll be protecting yourself from all complications of atherosclerosis.

Show Sources

Medline Plus web site: "Stroke secondary to atherosclerosis."
American Stroke Association publication: "What is a Stroke?"
American Stroke Association web site: "Atherosclerosis and Stroke;" "Reducing Risk;" and ''Types of Stroke.''
American Heart Association publication: "Heart and Stroke Facts."
Kleindorfer, D. Stroke, 2004; vol 35: pp e27-29.
Mark Silverman, MD, emeritus professor of medicine, Emory University School of Medicine, chief of cardiology, Piedmont Hospital, Atlanta.
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