All types of strokes involve the interruption of the blood supply to some area of your brain. Both blocked and leaking blood vessels result in a lack of oxygen and nutrients getting to brain cells. It takes only a few minutes after blood flow is interrupted—or even seconds—to kill millions of brain cells. 

  • Thrombotic or embolic strokes usually mean that some areas of your arteries are being damaged by atherosclerosis—a build-up of cholesterol and other fats, combined with calcium—that forms atherosclerotic “plaques.” Atherosclerosis in these areas results in blood clots that can suddenly clog up and block already narrowed arteries. Sometimes the narrowing occurs in the carotid arteries of your neck, stopping the blood from getting to your brain. In rare occasions, very low blood pressure can prevent enough blood from getting to the brain, such as when one is in shock.
  • Embolic strokes are often associated with an irregular or abnormal heart rhythm in one of the upper chambers of your heart (called an atrium). The abnormal rhythm is called atrial fibrillation. Atrial fibrillation may cause blood clots to form in your heart. These may travel up to your brain and cause an embolic stroke. 
  • Intracerebral hemorrhagic strokes are usually caused by uncontrolled high blood pressure (hypertension).
  • Subarachnoid hemorrhagic strokes are more likely to result from the breaking of a weak area of a blood vessel known as an aneurysm. Often, these weak areas are abnormalities that you are born with.

Lifestyle Factors

Your likelihood of having a stroke is higher if your lifestyle is unhealthy. The following lifestyle factors increase your stroke risk:

  • Obesity or being overweight
  • A diet high in saturated and trans fats and low in “good” fats
  • High salt intake
  • Alcohol abuse
  • Substance abuse (cocaine and other illegal drugs)
  • Smoking 

Medical Factors

Having certain medical conditions or diseases increases your chance of having a TIA or a stroke. These conditions include: 

  • Previous stroke or TIA
  • High blood pressure (hypertension). This is the number one risk factor for stroke.
  • Atrial fibrillation
  • Diabetes
  • Family history of stroke
  • High cholesterol
  • Older age (the risk increases for people over age 55)
  • Race (stroke is more likely to cause death in African Americans)
  • Heart disease
  • Atherosclerosis
  • Peripheral artery disease (PAD)–decreased blood flow, especially in your legs or in the carotid arteries in your neck
  • Other circulation problems that are not well-controlled, such as sickle cell anemia
  • Anemia that is left untreated

Updated: September 2017