Epidemiology of Hypertension 

Hypertension is a worldwide epidemic; accordingly, its epidemiology has been well studied in the United States and internationally.

National High Blood Pressure Education Program

In 1991, the National High Blood Pressure Education Program (NHBPEP) estimated 43.3 million adults had hypertension in United States.^[1] Hypertension was defined as systolic blood pressure (SBP) equal to or greater than 140 mm Hg and diastolic BP (DBP) as equal or more than 90 mm Hg or defined as those taking medication for hypertension. The prevalence according to age group, sex, and race is shown in Table 1, below.

Table 1. Prevalence (%) of Hypertension in the United States, 1989-1994^*[1] (Open Table in a new window)

NHANES and NCHS

According to data from the National Health Examination Surveys (NHANES), the age-adjusted prevalence of hypertension varies from 18-32%. The National Center for Health Statistic Surveys (NCHS) reported the awareness for hypertension increased from 53% over 1960-1962 to 89% over 1988-1991.^[2] The percentage of patients engaged in hypertension treatment increased from 35% to 79% during this period.^[2]

In a separate report, age- and sex-adjusted rates of prehypertension and stage I hypertension increased among non-Hispanic white, black, and Hispanic persons between 1988-1992 and 1999-2000; however, the age- and sex-adjusted rates of stage 2 hypertension decreased among non-Hispanic whites between 1988-1992 and 1999-2000, whereas they were unchanged for black and Hispanic persons.^[3]

A 2005 NHANES report in the United States found that in the population aged 20 years or older, an estimated 41.9 million men and 27.8 million women had prehypertension (SBP, 120-139 mm Hg; DBP, 80-99 mm Hg), 12.8 million men and 12.2 million women had stage 1 hypertension (SBP, 140-159 mm Hg; DBP, 90-99 mm Hg), and 4.1 million men and 6.9 million women had stage 2 hypertension (SBP ≥160 mm Hg; DBP ≥100 mm Hg).^[2]

Multi-Ethnic Study of Atherosclerosis

The Multi-Ethnic Study of Atherosclerosis is a US-based study that examined the associations of left ventricular (LV) mass and geometry with hypertension incidence in 2,567 normotensive participants. The study found that higher LV mass was associated with incident hypertension. Over 4.8 years, 745 participants developed hypertension.^[4]

Overall, approximately 20% of the world’s adults are estimated to have hypertension, when hypertension is defined as BP in excess of 140/90 mm Hg. The prevalence dramatically increases in patients older than 60 years: In many countries, 50% of individuals in this age group have hypertension. Worldwide, approximately 1 billion people have hypertension, contributing to more than 7.1 million deaths per year.^[5]

National health surveys in various countries have shown a high prevalence of poor control of hypertension.^[6] These studies have reported that prevalence of hypertension is 22% in Canada, of which 16% is controlled; it is 26.3% in Egypt, of which 8% is controlled; and it is 13.6% in China, of which 3% is controlled.

A progressive rise in BP with increasing age is observed. Age-related hypertension appears to be predominantly systolic rather than diastolic. The SBP rises into the eighth or ninth decade, whereas the DBP remains constant or declines after age 40 years.^[3]

The third NHANES survey reported that the prevalence of hypertension grows significantly with increasing age in all sex and race groups.^[7] The age-specific prevalence was 3.3% in white men (aged 18-29 y); this rate increased to 13.2% in the group aged 30-39 years. The prevalence further increased to 22% in the group aged 40-49 years, to 37.5% in the group aged 50-59 years, and to 51% in the group aged 60-74 years.^[7] In another study, the incidence of hypertension appeared to increase approximately 5% for each 10-year interval of age.

Cardiovascular disease risk

According to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VII), in individuals older than 50 years, SBP of greater than 140 mm Hg is a more important cardiovascular disease risk factor than DBP.^[8] Beginning at a BP of 115/75 mm Hg, the cardiovascular disease risk doubles for each increment of 20/10 mm Hg. Individuals who are normotensive (SBP < 120 mm Hg; DBP < 80 mm Hg) at 55 years will have a 90% lifetime risk of developing hypertension.

The age-adjusted prevalence of hypertension was 34%, 25.4%, and 23.2% for men and 31%, 21%, and 21.6% for women among blacks, whites, and Mexican Americans, respectively. NHANES III reported the prevalence of hypertension was 12% for white men and 5% for white women aged 18-49 years. However, the age-related BP rise for women exceeds that of men. The prevalence of hypertension was reported at 50% for white men and 55% for white women aged 70 years or older.^[3]

Black individuals have a higher prevalence and incidence of hypertension than white persons.^[9] The prevalence of hypertension has been reported to be increased by 50% in blacks. Most studies in the United Kingdom and the United States report not only a higher prevalence but also a lower awareness of hypertension in black people than in white people. Mortality from hypertension in African-Caribbean–born people is 3.5 times the national rate; similar data have been published for African American citizens.

The prevalence and incidence of hypertension in Mexican Americans are similar to or lower than those in non-Hispanic whites.^[10] NHANES III reported an age-adjusted prevalence of hypertension at 20.6% in Mexican Americans and 23.3% in non-Hispanic whites.^{[3, 7]} In general, Mexican Americans and Native Americans have lower BP control rates than non-Hispanic white persons and black individuals.^[11]

To understand ethnic influence, an understanding of the renin-angiotensin system (RAS) is essential. Renin secretion is suppressed when the kidney detects that the amount of sodium excretion is increased; thus, this is a clue to the excess sodium in the circulation. Black people tend to develop hypertension at an earlier age and have lower renin activity; target organ damage also differs in black people from that in white people.

In addition, black people have a poorer response to treatment with angiotensin converting enzyme (ACE) inhibitors compared with white people; the evidence for beta-blockers being less effective in black people is also clear. However, diuretics are more effective at a young age in black people.

In comparative assessments of black people and Asians, strokes are more common in black people, but coronary heart disease is more common in Asians. Both groups have a higher incidence of chronic renal failure than white people, but this is more due to hypertension in black people and diabetes in Asians.