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Stroke: Overview and Risk Factors

Stroke, an infarct in the brain, is the third–leading cause of death in the United States. About 80% of strokes are ischemic in origin and generally result from occlusion of a major cerebral artery by an embolus or thrombus. Global ischemia can occur after respiratory arrest or after cardiac events such as asystole or ventricular fibrillation. Hemorrhagic strokes occur when blood from a ruptured vessel (eg, an aneurysm) compresses and damages brain tissue. Venous strokes, due to thrombosis of the venous dural sinuses, are uncommon but may be associated with hypercoagulability, dehydration, and the use of estrogen.

A transient ischemic attack (TIA) produces similar signs and symptoms, but is transitory. It often resolves completely within 30 to 60 minutes, although symptoms may last several hours. Occurrence of a TIA indicates a need for thorough neurologic and cardiovascular evaluation of stroke risk.

Warning signs of stroke include the following sudden changes:

  • Numbness (paresthesia) or weakness (paresis) of the face, arm, or leg, usually on one side of the body.
  • Confusion, difficulty speaking (dysarthria or aphasia) or understanding.
  • Visual disturbances, which may include partial or complete vision loss.
  • Dizziness and/or ataxia.
  • Severe headache with no known cause—particularly with hemorrhagic strokes.

Risk Factors

Compared with whites, African Americans and Latinos have higher incidence and mortality rates of stroke. It is currently unclear whether these differences are due to environmental or genetic causes. Other risk factors include:

Age. The risk of stroke doubles every 10 years beyond age 55.1,2

Gender. Recent studies have shown that women now have a slightly higher prevalence of stroke than men. Case–fatality rates due to stroke are also higher in women.3

Hypertension is the most important modifiable risk factor, especially for hemorrhagic stroke. Both systolic and diastolic hypertension are associated with an increased risk. (For more information, see Hypertension chapter.)

Smoking. Cigarette smoking increases risk for ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. The risk is reduced to that of a nonsmoker within 2 to 5 years of smoking cessation.

Diabetes.

Hyperlipidemia.

Homocysteine. Elevated levels of homocysteine are thought to cause endothelial dysfunction, thus increasing risk for vascular disease and cerebrovascular pathology.4,5

Sedentary lifestyle. Higher levels of occupational or leisure–time physical activity protect against stroke.6 A study of women undergoing coronary angiography found that those with higher activity levels were at significantly lower risk for cardiovascular events, including stroke.7

Poor nutrition. High–fat, high–sodium diets and a lack of key nutrients such as folic acid have been associated with increased risk for stroke (see Nutritional Considerations).

Carotid stenosis. Both symptomatic and asymptomatic stenoses of the internal carotid arteries are associated with increased risk for ischemic stroke.8

Atrial fibrillation. In the Framingham Study, patients with atrial fibrillation had 5–fold greater risk of stroke than their healthy counterparts.9 Further, the attributable risk of stroke due to atrial fibrillation increased with age from 1.5% for persons aged 50 to 59 years, to 23.5% for those aged 80 to 89 years.9

Vasculitis.

Sickle cell disease.

Migraine. Studies have found that migraines with aura were strongly associated with both symptoms and actual risk of stroke and TIA.10 Hemiplegic and basilar migraines are also risk factors.

Alcohol abuse.

Drug abuse. Abuse of cocaine and amphetamines may result in hemorrhage.

 

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Stroke: Diagnosis and Treatment >>