Identify Stroke Risk Factors

Nonmodifiable stroke risk factors include age, gender, heredity, and ethnicity. There is an exponential increase in incidence of stroke with age, and the majority of strokes occur in persons over 65 years of age. Men have a greater stroke incidence than women, but women often live long enough to experience stroke and, therefore outnumber men in some stroke studies. A history of maternal stroke appears to be another gender-related risk factor. Stroke mortality among African-Americans is double that of white Americans. The incidence of stroke has been found to be greater in African-Americans, but further study is needed to assess the importance of referral and selection biases, confounding risk factors, and differential access to medical care. Little information is available regarding the rapidly growing Hispanic population.

Major reductions in stroke morbidity and mortality are more likely to arise from identification and control of modifiable factors in the stroke-prone individual. Modifiable stroke risk factors include: hypertension, cardiac disease (particularly atrial fibrillation), diabetes, hypercholesterolemia, asymptomatic carotid stenosis, cigarette use, alcohol abuse, and transient ischemic attacks.

Hypertension, after age, is the most powerful stroke risk factor. It is prevalent in the US population in both men and women, and is of even greater significance in African-Americans. The risk of stroke rises proportionately with increasing blood pressure. Isolated systolic hypertension is increasingly prevalent with age and increases the risk of stroke by 2 to 4, even after controlling for age and diastolic blood pressure. Since the attributable stroke risk for hypertension (proportion of strokes explained by hypertension) ranges from 35% to 50% depending on age, even a slight improvement in the control of hypertension could translate into a substantial reduction in stroke frequency.

Cardiac disease has been clearly associated with an increase in the risk of ischemic stroke. Since certain stroke risk factors, like hypertension, may also be determinants of cardiac disease, some cardiac conditions may be viewed as intervening events in the causal chain for stroke. Cardiac factors which have been documented to independently increase the risk of stroke include: atrial fibrillation, valvular heart disease, myocardial infarction, coronary artery disease, congestive heart failure, electrocardiographic evidence of left ventricular hypertrophy, and perhaps mitral valve prolapse. It should also be noted that chronic atrial fibrillation is a major predictor of stroke, accounting for 7% to 30% of all strokes in patients over age 60. When atrial fibrillation was associated with rheumatic valvular heart disease, Framingham Study investigators found an 18-fold rise in stroke incidence; nonvalvular atrial fibrillation conferred nearly a 5-fold greater risk. Improved cardiac imaging has led to the increased detection of potential stroke risk factors: mitral valve prolapse, mitral annular calcification, patent foramen ovale (PFO), aortic arch atherosclerotic disease, atrial septal aneurysms, and spontaneous echo contrast (a smokelike appearance in the left cardiac chambers visualized on transesophageal echocardiography).

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