Stroke, also known as a cerebrovascular accident (CVA), occurs when the blood supply to part of the brain is interrupted, causing the cells to die within minutes. Brain damage from stroke can continue for several days after the event. 

Stroke is the third-leading cause of death in the United States, affecting about 700,000 individuals each year. Individuals with diabetes are two to four times more likely to have a stroke than nondiabetics, according to the U.S. Centers for Disease Control and Prevention (CDC).

Stroke is a life-threatening condition that requires immediate medical treatment. Delaying treatment can result in neurological and tissue damage (e.g., permanent speech loss or paralysis) or even death.

There are two types of stroke:

• Ischemic stroke. About 88 percent of strokes are caused by a severe episode of cerebral ischemia (a reduction in the blood supply to the brain). Ischemic strokes typically occur when a blood clot blocks an artery leading to the brain. The blood clot can either form inside the artery (a thrombus) because of atherosclerosis (a condition characterized by excess plaque on the inner arterial walls), or it can travel through the bloodstream from another part of the body and become lodged inside the artery (an embolus). These conditions are called thrombotic stroke and embolic stroke, respectively.
  

  

• Hemorrhagic stroke. This type of stroke occurs when blood from the arteries leaks into the brain after a rupture. In addition to starving some parts of the brain of essential blood and oxygen, the accumulated blood (hemorrhage) may cause further damage by exerting pressure on the surrounding tissue. Bleeding within the brain (cerebral hemorrhaging) accounts for about 9 percent of strokes, whereas bleeding around the brain (subarachnoid hemorrhaging) only accounts for about 3 percent of strokes. Cerebral hemorrhaging is often caused by high blood pressure which, according to the National Diabetes Education Program, affects 70 percent of people with diabetes. Subarachnoid hemorrhaging may be caused by a ruptured cerebral aneurysm (a bulging formation on the arterial wall), a head injury or other factors. Hemorrhagic strokes generally affect younger patients.

People with type 1 diabetes have an increased risk of stroke because high quantities of glucose (blood sugar) can damage blood vessels over time, making arterial walls thicker and less flexible and hindering the passage of blood. Hyperglycemia also puts individuals with type 2 diabetes at risk, and in addition they may experience vascular damage from persistently high levels of the glucose-regulating hormone insulin (hyperinsulinemia).  Diabetic individuals also tend to have higher levels of fats (lipids) in their blood, which can clog and narrow blood vessels, resulting in atherosclerosis. Additionally, people with diabetes are more prone to blood clots than nondiabetics.

Individuals with diabetes are also more likely to have high blood pressure, coronary artery disease, obesity and many other risk factors for stroke. However, numerous studies indicate that people with diabetes have a greater stroke risk than nondiabetics regardless of how many risk factors they exhibit.