Hypertension and Risk of Stroke: The Influence of Associated Risk Factors in the Framingham Study

Abstract

Hypertension is the pre-eminent risk factor for stroke with incidence of both ischemic stroke and hemorrhage increasing with level of blood pressure. However, at any blood pressure level, risk of stroke varies widely according to the presence and intensity of other risk factors. These include: age; antihypertensive therapy; presence of cardiovascular disease; cigarette smoking; diabetes; LVH by ECG; and atrial fibrillation. Without risk factor abnormalities, a hypertensive individual may actually have a lower probability of stroke than a normotensive with multiple elevated risk factor levels. The person with multiple borderline risk factor levels is particularly difficult to categorize. To determine probability of stroke, taking the risk factor and blood pressure levels into account, a stroke risk profile was developed using Framingham Study data. Key to the usefulness of the risk profile is the knowledge, derived from observational studies and controlled clinical trials, that modification of a number of these risk factors can reduce the incidence of stroke. These include: reduction of elevated blood pressure, systolic as well as diastolic; cessation of cigarette smoking; improved control of blood sugar level in diabetics; and treatment of persons with atrial fibrillation with low intensity warfarin. Thus, the Framinghan stroke risk profile may guide the physician in identifying patients at heightened risk, and provide guidance in measures that can reduce the likelihood of stroke. (Hypertens Res1994; 17 Suppl. I: S83-S88)