Risk of cardiovascular disease (CVD) increases incrementally with blood pressure, even within the high-normal range. In the general population, 27% of CVD in women and 37% in men is attributable to hypertension. A high percentage of these hypertension-related events occur in those with high-normal blood pressure and mild hypertension; about one-fourth of CVD events in elderly women and one-third in elderly men in the Framingham Study occured in persons who had blood pressures of 140–159mm Hg systolic and/or 90–95mm Hg diastolic. The average systolic blood pressure (SBP) at which coronary heart disease occurs is rather modest (141mm Hg), as is the pulse pressure (59–63mm Hg). Of the CVD events in elderly participants in the Framingham Study, 24% in men and 36% in women occurred in persons receiving treatment for hypertension.
There is a growing recognition of the importance of the systolic component of blood pressure. About 65% of hypertension in the elderly is isolated systolic hypertension (ISH), and CVD risk increases with pulse pressure. Pulse pressure is not simply a marker for stiff diseased arteries; treatment of ISH in trials promptly reduces the CVD risk, indicating that the pulse pressure generated by the stiff artery is the culprit. Analysis of data from clinical trials indicates that greater reliance should be placed on systolic pressure in evaluating the CVD potential of hypertension.
Hypertension, including ISH, seldom occurs in isolation from other risk factors and overt CVD. Risk varies widely depending on the burden of accompanying risk factors. This makes global risk assessment mandatory for evaluating risk and the urgency and nature of treatment required.
Evidence incriminating systolic pressure as the dominant blood pressure determinant of CVD has not been translated into clinical practice. Most of the uncontrolled hypertension observed in the Framingham Study is concentrated in those with ISH. This also extends to African-Americans, people with diabetes mellitus and the elderly.
When should SBP be considered controlled? Substantial evidence supports the value of treating ISH with SBP exceeding 160mm Hg. Trial data are not yet available to support recommendations to treat lesser elevations of ISH or pulse pressure per se, but since one-half of patients with mild ISH have two or more additional risk factors, most are candidates for treatment. In such patients, ISH should be considered controlled when their global CVD risk is reduced to below the average for their age.