Common Types of Hypertension
Physicians classify the different kinds of hypertension based on their causes and characteristics. Some of the most common types are described below.
About 90% to 95% of people with high blood pressure have what’s called essential hypertension or primary hypertension. This means the condition has no identifiable source. Most experts believe essential hypertension is caused by a variety of factors, many of them as yet unknown. If this hypothesis is correct, it may explain why certain treatments lower blood pressure in some people, but not in others. For example, people who are salt-sensitive (see “Excess salt”) sometimes control their blood pressure with a low-sodium diet alone, while others find sodium intake has little or no influence on their hypertension.
Isolated systolic hypertension
As people age, their arteries tend to lose elasticity and become less able to accommodate surges of blood. The damage created in the vessel lining when blood flows through the arteries at high pressure can accelerate plaque buildup. Eventually, plaque deposits lead to atherosclerosis (hardening of the arteries). Atherosclerosis can elevate systolic blood pressure, while diastolic pressure stays in the normal range. A systolic pressure of 140 or greater coupled with a diastolic reading of 89 or below is called isolated systolic hypertension. This is the most common form of high blood pressure in the elderly. The Framingham Heart Study, which has tracked the health of participants since the late 1940s, found that 65% to 75% of people over age 65 with elevated blood pressure had isolated systolic hypertension (see Figure 3).
In the past, doctors considered isolated systolic hypertension to be normal in elderly patients and saw no reason to treat it. However, in 1991, the Systolic Hypertension in the Elderly Program (SHEP) provided strong evidence to the contrary. SHEP tracked 4,736 patients with isolated systolic hypertension over five years. Half the participants were placed on drugs to reduce blood pressure, while the other half received a placebo. Those taking medication had significantly fewer strokes and heart attacks than the placebo group. The SHEP study has spurred doctors to treat isolated systolic hypertension more aggressively in older patients.
Figure 3: Isolated systolic hypertension increases with age
People usually think of systolic and diastolic pressure rising in tandem, but that isn’t necessarily the case. In fact, by age 60, most people with high blood pressure have what’s called isolated systolic hypertension — a systolic blood pressure above 140 with a normal (under 90) diastolic pressure. This form of hypertension becomes more common with age.
Source: Franklin SS, et al. Hypertension (2001), Vol. 37, pp. 869–74.