High Blood Pressure

Both systolic and diastolic blood pressure increase with age. However, diastolic blood pressure increases with age until the age of fifty or sixty and then tends to remain stable or even decrease slightly, whereas systolic blood pressure rises progressively until the age of seventy or eighty. This combination of changes probably reflects stiffening of the blood vessels and reduced arterial elasticity and leads to a large increase in pulse pressure (the difference between the systolic and diastolic pressures) with aging (Burt et al.). In persons over eighty, a decrease in both diastolic and systolic blood pressure has been found in some studies, and may be due to poor health in this very frail population. The global prevalence of both diastolic and systolic hypertension in people over sixty-five is about 45 percent. Hypertension is more frequent in black than white persons, and in women than men. The prevalence of isolated systolic hypertension is about 7, 11, 18, and 25 percent in people aged sixty to sixty-nine, seventy to seventy-nine, eighty to eighty-nine, and over ninety, respectively. Isolated systolic hypertension is more frequent in women than men.

The mechanisms of hypertension in elderly persons involve an increase in thickness of aortic and large artery walls and a decrease in vessel elasticity, which raises systolic blood pressure. Hypertension also increases peripheral vascular resistance, because of the reduced elasticity of these arteries. In addition, it reduces the sensitivity of nerve endings stimulated by pressure changes, resulting in the impairment of postural reflexes, which makes elderly persons with hypertension prone to hypotension when standing erect. The vasoconstriction due to changes in the balance between beta-adrenergic vasodilatation and alpha-adrenergic vasoconstriction raises peripheral vascular resistance and blood pressure. Increased sodium intake and decreased sodium excretion induce sodium retention. In contrast to hypertension in younger adults, the reninangiotensin system is not thought to play a major role in hypertension in older adults.