Wednesday, February 28, 2007

Modifiable risk factors for stroke

In 2001, the Stroke Council of the American Heart Association (AHA) issued a scientific statement on the primary prevention of ischemic stroke (Goldstein, 2001). The statement was based on the findings of an ad hoc writing group formed by the AHA council to review pertinent literature, published guidelines, and expert opinions regarding risk factors for ischemic stroke. 

According to the AHA council, each recommendation was based on five different levels of evidence. Further classification within the AHA scientific statement included the potential for modification (nonmodifiable, modifiable, or potentially modifiable) of the identified risk factor and the strength of evidence (well documented or less well documented).

Nonmodifiable risk factors included age, sex, race/ethnicity, and family history of stroke or TIA. Well-documented modifiable risk factors (all level I [data from randomized trials with low false-positive and low false-negative errors], grade A [supported by level I evidence]) included hypertension, smoking, diabetes/hyperinsulinemia/insulin resistance, asymptomatic carotid stenosis, atrial fibrillation, other cardiac disease (eg, valvular heart disease, intracardiac congenital defects), sickle cell disease, and hyperlipidemia. Less well-documented or potentially modifiable risk factors included hyperhomocysteinemia, obesity, physical inactivity, alcohol and drug abuse, hypercoagulability, hormone replacement therapy, oral contraceptive use, and inflammatory processes.

Hypertension was considered a major risk factor for stroke, as it remains underdiagnosed and inadequately treated. The relationship between stroke and systolic and diastolic blood pressures is direct, continuous, and apparently independent. More than 30 years of evidence reveals that adequately controlled hypertension is a factor in preventing stroke, as are beta-blocker and high-dose diuretic therapy. Particularly in elderly persons, isolated systolic hypertension is considered an important risk factor for stroke (systolic blood pressure of more than 160 mm Hg and diastolic blood pressure of less than 90 mm Hg). One trial involving 4,695 elderly patients with isolated systolic hypertension was terminated when a stroke reduction rate of 42% was reached in the patients who were actively treated with antihypertensive therapies (a long-acting dihydropyridine calcium antagonist as initial therapy and other drugs as part of step-two drug titration) compared with those taking placebo (Staessen, 1997).  The AHA recommends that adult patients undergo routine screening for hypertension at least once every two years. 

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