Risk stratification in hypertension: new insights from the Framingham study*1

Abstract

Five decades of epidemiologic research have established that blood pressure elevation is a common and powerful contributor to all of the major cardiovascular diseases, including coronary disease, stroke, peripheral artery disease, renal disease, and heart failure. The common variety of hypertension designated benign essential hypertension was not shown to be either benign or essential. Although clinicians favor the diagnosis and treatment of hypertension in terms of diastolic blood pressure elevation and categoric cut points, epidemiologic data show a more important influence of systolic blood pressure, and a continuous, graded influence of blood pressure even within what is regarded as the normotensive range. An important revelation in epidemiologic hypertension research is that hypertension usually occurs in conjunction with other metabolically linked risk factors; therefore, less than 20% occurs in isolation. The other risk factors that tend to accompany hypertension include glucose intolerance, obesity, left ventricular hypertrophy, and dislipidemia (elevated total, LDL, and small dense LDL cholesterol levels, raised triglyceride, and reduced HDL cholesterol levels). Clusters of three or more of these additional risk factors occur at four times the rate expected by chance. This clustering is attributed to an insulin resistance syndrome promoted by abdominal obesity. The amount of risk factor clustering accompanying elevated blood pressure was observed to increase with weight gain. Based on Framingham Study data the prevalence of insulin resistance syndrome in the general population could be as high as 22% in men and 27% in women. Risk of coronary disease, the most common and most lethal sequel to hypertension, increased stepwise with the extent of risk factor clustering. Among persons with hypertension, about 40% of coronary events in men and 68% in women are attributable to the presence of two or more additional risk factors. Only 14% of coronary events in hypertensive men and 5% of those in hypertensive women occurred in the absence of additional risk factors. Other important features of risk stratification of hypertension are the presence of an elevated heart rate and left ventricular hypertrophy, and an elevated fibrinogen that often accompany hypertension. Recent population-based data reported suggest that elevated renin accompanying hypertension may independently enhance the risk of coronary events. Because clustering of other major risk factors with hypertension is the rule, the prudent physician should routinely screen for the presence of these other factors. Multivariate risk assessment profiles are now available for coronary disease, stroke, peripheral artery disease, and heart failure, to enable physicians to pool all the relevant risk factor information so as to arrive at a composite risk estimate. Hypertensive patients are more appropriately targeted for therapy by such risk stratification and the goal of the therapy should be to improve the multivariate risk profile.