More than 1 billion individuals worldwide, including 50 million Americans, have high blood pressure warranting some form of treatment.1-4 Higher-than-optimal blood pressure is the number one attributable risk for death throughout the world, and approximately 7.6 million deaths per year are attributed to uncontrolled hypertension.3 As life expectancy continues to increase, hypertension will become an even more important medical and public health issue because blood pressure typically increases with aging in most industrialized countries. In the United States, 50% of people 60 to 69 years old and approximately 75% of people 70 years old and older have hypertension.1,2 In some isolated, nonindustrialized populations, however, blood pressure does not increase with increasing age, and only a small fraction of the population develops hypertension. This suggests that predisposing environmental factors play a major role in causing hypertension and that an increase in blood pressure with aging is not inevitable when these factors are absent.
A direct positive relationship between blood pressure and cardiovascular disease (CVD) risk has been observed in men and women of all ages, races, ethnic groups, and countries, regardless of other risk factors for CVD.4 Observational studies indicate that death from CVD increases progressively and linearly as blood pressure increases above 115 mm Hg systolic and 75 mm Hg diastolic pressure.3 For every 20-mm Hg systolic or 10-mm Hg diastolic increase in blood pressure, there is a doubling of mortality from both ischemic heart disease and stroke in all age groups from 40 to 89 years old.5
Despite major advances in our understanding of its pathophysiology and the availability of many drugs that can effectively reduce blood pressure in most hypertensive subjects, hypertension continues to be the most important modifiable risk factor for CVD.
Blood pressure is a variable quantitative trait with a normal distribution that is slightly skewed to the right. Although there is no clear level of blood pressure where CVD begins to occur, a definition of hypertension, although somewhat arbitrary, is useful for making decisions about treatment. A commonly used blood pressure classification was proposed in 2003 by the Seventh Report of the United States Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) (Table 69–1).6 This classification is based on the average of two or more blood pressure readings after an initial screening visit and is for individuals who are not taking antihypertensive medication and who are not acutely ill. When systolic and diastolic blood pressures fall into different categories, the JNC 7 recommends that the higher category be selected to classify the person's blood pressure.
Table 69–1. Classification of Blood Pressure for Adults Ages 18 Years and Older According to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure 7a