Stroke Causes and Risk Factors

Some risk factors for a stroke can be controlled or eliminated, while others cannot.

A stroke happens when blood that carries oxygen to the brain is blocked.

There are two main types of stroke: ischemic and hemorrhagic.

Causes of Ischemic Stroke

Ischemic strokes are caused by blood clots that block blood flow to the brain.

Blockages can form when the arteries supplying blood to the brain become narrowed by a build-up of plaque.

Plaque is a combination of fat, cholesterol and other substances that build up in the inner lining of the artery wall.

This condition is often referred to as atherosclerosis, or “hardening of the arteries.”

Causes of Hemorrhagic Stroke

Hemorrhagic strokes are caused by bleeding in or around the brain.

Bleeding occurs when a weakened blood vessel in the brain ruptures and leaks into the surrounding brain tissue.

The leaked blood can put too much pressure on the blood cells in the brain, causing damage.

Chronic high blood pressure is the most common reason for hemorrhagic stroke.

Two types of weakened blood vessels can cause hemorrhagic stroke:

  • Aneurysm, an abnormally shaped weak point in a blood vessel
  • Arteriovenous malformations (AVMs), clusters of abnormally formed blood vessels

Major Risk Factors for Stroke

Certain environmental factors, medical conditions, and lifestyle habits increase your risk of stroke.

Some risk factors can be treated or controlled, while other risk factors cannot.

Factors that can’t be changed include:

  • Family history: Stroke often runs in families. Your stroke risk may be higher if a grandparent, parent, or sibling has suffered a stroke in the past.
  • Age: Stroke is most common in adults over the age of 65. The chance of having a stroke doubles for each decade of life after 55, according to the American Stroke Association.
  • Gender: Women have more strokes than men, and strokes kill more women than men each year.
  • Race: African Americans, Hispanics, American Indians, and Alaska Natives have a higher risk of stroke than non-Hispanic whites or Asians.
  • Personal history of a previous stroke.

Stroke risk factors that can be prevented or controlled include:

  • High blood pressure: High blood pressure is the main risk factor for stroke. It can damage and weaken arteries throughout the body so that they burst or clog more easily.
  • High cholesterol: Cholesterol is a fatty substance that contributes to plaques in the arteries that can block blood flow to the brain.
  • Heart disease: Coronary artery disease, the build-up of plaque in the arteries, can increase your risk of stroke. So can other heart conditions, including heart valve defects and irregular heartbeat (atrial fibrillation).
  • Diabetes: People with diabetes are four times as likely to have a stroke as people without diabetes, according to the National Stroke Association.
  • Sickle cell anemia.

Other Risk Factors for Stroke

Certain lifestyle habits and conditions can also increase your risk of stroke.

These risk factors include:

  • Smoking
  • Poor diet
  • Obesity
  • Low physical activity
  • Stress and depression
  • Heavy alcohol use
  • Use of illicit drugs, including cocaine and amphetamines.

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