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Causes

All strokes stop blood flow to part of the brain. Whether a blood vessel is blocked or leaking, the brain does not get enough oxygen and nutrients. Brain cells can start to die within minutes after blood flow stops.

Types of Strokes and Causes

Thrombotic Stroke

This type usually happens when blood vessels have atherosclerosis. That is a buildup of cholesterol, fat, and calcium inside the vessel walls. This buildup is called plaque.

Plaque makes arteries narrow. Blood clots can then suddenly block these already-narrow arteries. Sometimes clots form in the carotid arteries in the neck. This stops blood from reaching the brain.

Embolic strokes

These strokes often happen when the heart beats in an abnormal way. This is called atrial fibrillation. It affects one of the upper chambers of the heart. This abnormal rhythm can cause blood clots to form in the heart. Those clots can travel up to the brain and cause a stroke.

Intracerebral hemorrhagic strokes

This type of stroke is usually caused by high blood pressure that is not controlled (hypertension).

Subarachnoid hemorrhagic strokes

These strokes usually happen when a weak spot in a blood vessel breaks. This weak spot is called an aneurysm. Many people are born with these weak areas.

Lifestyle Factors

An unhealthy lifestyle raises stroke risk. Risk increases with:

  • Obesity or being overweight
  • A diet high in unhealthy fats (saturated and trans fats) and low in "good" fats like those found in plants.
  • High salt intake
  • Heavy alcohol use and smoking
  • Misuse of substances, including cocaine and other illegal drugs.

Medical Factors

Certain health conditions raise the chance of having a stroke. They include:

  • Previous stroke and family history of stroke
  • High blood pressure (hypertension) - this is the number one risk factor for stroke.
  • High cholesterol
  • Heart disease, including atrial fibrillation.
  • Diabetes
  • Advanced age
  • Certain racial and ethnic backgrounds
  • Atherosclerosis and peripheral artery disease (PAD). PAD happens when plaque builds up in blood vessels that carry blood to the legs and neck. This can reduce blood flow to those areas.
  • Blood disorders, such as anemia and sickle cell anemia

 

Last Reviewed and Updated: October 2026 
By: AGS/HiAF Public Education Committee, HealthinAging.org Content Reviewers

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