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.
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.
CLASSIFICATION AND SUBTYPES OF HYPERTENSION
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.
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.
Three-dimensional classification of hypertension according to severity (height of the blood pressure), etiology (primary vs secondary), and age. BP, blood pressure.
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 no longer used. Malignant hypertension is now relatively uncommon in Western countries, but it does still occur and, when present, it requires urgent treatment, which can dramatically alter its natural history.
In hypertensive patients, either or both the systolic and diastolic BP are elevated, but elevations in systolic BP are most common. In particular, the most common circumstance is isolated systolic hypertension where the systolic BP is elevated, but the diastolic BP normal, occurring predominantly in older persons. Isolated diastolic hypertension can also occur and is the most common hypertensive subtype in younger persons. Hypertension can also be the result of the ...