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Summary
This chapter discusses the definition and classification of hypertension, its prevalence, treatment and control, as well as risk factors for and risks of the condition. According to JNC 7, normal blood pressure (BP) is defined as systolic blood pressure (SBP) <120 mm Hg and diastolic blood pressure (DBP) <80 mm Hg. Individuals with SBP of 120-139 mm Hg or DBP of 80-89 mm Hg are classified as having prehypertension. Individuals with SBP of 140-159 mm Hg or DBP of 90-99 mm Hg are classified as having stage 1 hypertension whereas those with SBP ≥160 mm Hg or DBP ≥100 mm Hg are considered to have stage 2 hypertension. In the USA, ~33% of adults aged ≥20 years have hypertension; prevalence is highest among non-Hispanic blacks, and increases with age and body-mass index. In the period 2007-2012, ~77% of hypertensive individuals were being treated and ~54% had their hypertension under control. In addition to age, race/ethnicity, and body-mass index, other major risk factors for hypertension include tobacco use and diet (see accompanying Hurst's Central Illustration). Among individuals aged <60 years, men are more likely to have the condition; the inverse is true among older adults. Hypertension significantly increases the risk of stroke and cardiovascular disease, and is the top attributable cause of death worldwide.
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Elevated blood pressure (BP) is the top attributable cause of mortality globally, responsible for some 7.5 million deaths annually (approximately 12.8% of all deaths) and accounts for 57 million disability-adjusted life years.1 Global prevalence of elevated BP in 2008 was approximately 40%, being highest (46%) in the World Health Organization African region and lowest in the Americas, around 35% overall for both men and women. Approximately one billion persons throughout the world have uncontrolled hypertension, an increase from 600 million in 1980.
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Hypertension is the most prevalent chronic condition in the United States and the most common reason for an office visit to a physician. It accounts for the most drug prescriptions and is one of the most important risk factors for heart disease and stroke.2 This chapter reviews the epidemiology of hypertension—how it is defined and classified, the extent of its prevalence, treatment, and control, and its relation to cardiovascular and other consequences.
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CLASSIFICATION AND SUBTYPES OF HYPERTENSION
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Hypertension can be quantified on the basis of a large number of epidemiologic studies showing that the distribution of BP in the population is continuous, although the curve is skewed at the higher levels of BP. The unimodal distribution of BP implies that hypertension is unlikely to be the result of a single physiologic process or gene, and perhaps most importantly suggests that any BP level used to define hypertension is arbitrary.
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Hypertension can be classified in different ways—helpful for its diagnosis and clinical management (Fig. 23–1). The two principal divisions are severity (the height of the BP) and underlying cause (primary or essential hypertension vs secondary hypertension). A third major component is age: the pathophysiology of hypertension in younger and older people is quite different.
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The original subdivision of hypertension according to its severity was benign and malignant. Although malignant hypertension carries a prognosis that is equivalent to that of other malignant diseases (if untreated), the term benign for less severe forms of hypertension is a misnomer and is ...