Introduction

Hypertension is the most prevalent of all cardiovascular diseases in the United States, affecting an estimated 58 million Americans, or about one-fourth of the population. The causes of high blood pressure are multifactorial and only partially understood. The prevalence of hypertension increases with age and is higher among Blacks. Prevalence is also higher among younger males than females, especially in the white population. Persons who smoke cigarettes and who are overweight are at increased risk of morbidity and mortality from hypertension though causal relationships are unclear. High blood pressure is a major risk factor for the development of coronary heart disease and stroke. Approximately one-half of those who suffer a heart attack and two-thirds of those who suffer a stroke have hypertension. High blood pressure contributes to an estimated 250,000 deaths each year from coronary heart disease, stroke, congestive heart failure, and kidney disease.

From 1964 to 1984, the mortality rates for coronary heart disease declined 40% and for stroke 55%. Increased public awareness and improved control of high blood pressure may have contributed to the declining cardiovascular disease death rates.

Figures regarding the prevalence of high blood pressure in the U.S. are based largely on data from the 1976-80 National Health and Nutrition Examination Survey (NHANES II). The NHANES II study averaged three blood pressure readings taken during a single visit from a representative sampling of the civilian noninstitutionalized population. Clinical studies have demonstrated the benefit of treating mild hypertension; therefore, the threshold for diagnosis of hypertension has been lowered. Currently 140/90 mm Hg is considered the upper limit of normal blood pressure and that value is used for determining hypertension prevalence. Prior to 1980, however, 160/95 mm Hg was considered by many to be the upper limit of normal blood pressure, so for comparison with previous years, 160/95 is used and appropriately identified.

Prevalence

Hypertension

Based on 1983 projections from national survey data, 58 million Americans, or about 30% of the adult population, are estimated to be at increased risk of morbidity and premature mortality associated with high blood pressure.

The 1976-1980 National Health and Nutrition Examination Survey (NHANES II) showed that hypertension is more prevalent among Blacks (38.2%) than whites (28.8%) and more common among men (33.0%) than women (26.8%) especially at younger ages.

The prevalence of high blood pressure increases with age, from 9.2% of those aged 18-24 years to 64.3% of those 65-74 years, according to NHANES II data.

An estimated 75% of persons over the age of 75 years have hypertension.

0.6% of the U.S. population was found to have severe high blood pressure (diastolic higher or equal to 115 mm Hg) in the NHANES II study. However, the prevalence of severe high blood pressure among Black males (2.2%) was more than 4 times the prevalence among white males (0.5%); and the prevalence among Black females (0.8%) was 2 times that of white females (0.4%).

Hypertension prevalence varies by region, with 31% of those in the South having hypertension compared to 29% of those in all other areas. The difference is most evident among Black females who have a hypertension prevalence of 44% in the South as compared to 34% of all other regions.

The prevalence of severe hypertension (diastolic pressure higher or equal to 115 mm Hg) is greater in the South (2.4%) than elsewhere (1.7%), especially among Blacks in the South, who have a prevalence of severe hypertension that is 2.6 times the prevalence among Blacks in all other regions.

Control of High Blood Pressure

The NHANES II study found that 34.2% of hypertensive persons controlled their blood pressures to below 160/95 and 11.1% to below 140/90. There was little racial difference in blood pressure control status, but 43.0% of women were controlled to below 160/95 compared to 24.2% of men.

According to the NHANES II data, 55.6% of persons with blood pressure higher or equal to 160/95 were on antihypertensive medications, compared to 33.1% of persons with blood pressures higher or equal to 140/90.

The Hypertension Detection and Follow-Up Program (HDFP) revealed that 60% of hypertensives were more than 20% above ideal weight, as compared to 24% of adult females and 18% of adult males in the general U.S. population.

The HDFP also reported a 17% decline in overall mortality, a 45% decline in stroke mortality and a 26% decline in heart attack mortality among hypertensive patients in an intensive, stepped-up-care program, compared to hypertensives referred for routine care in the community.

Morbidity and Mortality Associated with Hypertension

Hypertension limits the activities of nearly 3 million persons in the United States.

The National Heart, Lung and Blood Institute estimates that approximately one-half of those who suffer a heart attack and about two-thirds of those who suffer a stroke have hypertension.

Hypertension contributes to an estimated 250,000 deaths each year from stroke, coronary heart disease, congestive heart failure and kidney disease.

Mortality figures for 1984 list 31,341 deaths in the U.S. with hypertension as the underlying cause. In addition, hypertension was a major contributor to the 154,327 stroke deaths as well as many of the 541,288 deaths from schemic heart disease in 1984.

The prevalence of hypertension among Blacks (38.2%) is 33% higher than among whites (28.8%), but the stroke mortality rate among Blacks (58.3 deaths per 100,000) is nearly double that for whites (32.0 per 100,000). The stroke mortality among persons under 65 years of age for Blacks is nearly 3 times that for whites.

Hypertension may cause 30% of all cardiovascular disease deaths including 29% of coronary heart disease deaths and 32% of stroke deaths, according to a report by the Carter Center.

The same Carter Center report estimated that the number of cardiovascular disease deaths that could be averted each year if high blood pressure were eliminated is as high as 292,504, including 164,837 coronary heart disease deaths and 54,642 stroke deaths.

Public and Professional Awareness

The NHANES II study showed that at the 160/95 threshold 73.4% of hypertensives were aware of their high blood pressure problem. Awareness was higher among women (81.3%) than men (64.6%) and higher among Blacks (80.1%) than whites (72.5%).

Awareness of hypertensive status among persons with blood pressures 160/90 or taking antihypertensive medication in the NHANES II study increased with age from 43.8% of persons 18-24 years of age to 79.7% of those 65-74 years of age.

A 1984 national study showed that about 80% of the public realized that hypertension may be related to diet, while 50% of the public was aware of the association between sodium and hypertension.

The same 1984 study revealed that 38% of the American public has reduced or is attempting to reduce sodium intake. Most of those attempting to reduce sodium intake do so by restricting use of the salt shaker, with 28% of those attempting to reduce sodium intake restricting their selection of foods.

A 1985 National Health Interview Survey (NHIS) showed that 51% of males and 61% of females reported having had their blood pressure checked within 6 months; however, 32% of males and 21% of females reported not having had their blood pressure checked in over a year.

The same NHIS study revealed that 91% of the public is aware of the association between high blood pressure and heart disease, and 93% know that being overweight increases the risk of heart disease.

Among persons 35-74 years of age in the U.S., 29% of white males, 31% of white females, 35% of Black males and 55% of Black females are overweight (defined as body mass greater than the sex-specific 85th percentile for persons 20-29 years of age).

Service Delivery

The National High Blood Pressure Education Program, begun in 1972, is a coalition of about 15 Federal agencies, 150 national organizations, virtually all state health departments, and more than 2,000 community-based programs. It is coordinated by the National Heart, Lung and Blood Institute of the National Institutes of Health. Its mission is the promotion of nationwide efforts to detect, treat and control hypertension through public, patient, and professional education programs.

The most recent National Ambulatory Medical Care Survey (1981) lists hypertension as the leading principal diagnosis in visits to doctors' offices in 1981, constituting 28.8 million visits or 4.9% of all visits.

In 1984, 266,000 hospital discharges listed hypertension as the principal diagnosis. The average length of stay for patients hospitalized for hypertension was 5.6 days. Of those hospitalized for hypertension, 18% were of persons ages 15-44; 43% of ages 45-64; and 38% of those over age 65.

In 1982, the most frequently dispensed prescription drug in the United States was hydrochlorothiazide, a diuretic commonly used for the control of high blood pressure. More than 5% of all prescriptions, or 78.2 million prescriptions, contained hydrochlorothiazide in 1982.

Drugstores and hospitals in 1982 spent a total of $1.7 billion on cardiovascular drugs in addition to $500 million on diuretics.

In 1984, the Department of Health and Human Services allocated $18 million in block grants for programs to control high blood pressure.

In 1983, the direct and indirect costs for all cardiovascular diseases were estimated at $102 billion.

Significant Trends

Prevalence, Awareness, Treatment and Control

The National Health and Nutrition Examination Surveys (NHANES I, IA and II), using a high blood pressure threshold of 160/95 mm Hg, provide a means of comparing data collected from 1971 through 1980 on the prevalence, awareness, treatment and control of high blood pressure in the U.S., as summarized in the following table.

Public Knowledge and Behavior

From 1972 to 1985, visits to office-based physicians for hypertension increased 58%, whereas visits for all causes increased by only 7%.

Mortality

Mortality attributed to hypertension has declined an estimated 7% per year in the 1970s as a result of earlier detection and more vigorous treatment. The decline in hypertension mortality has contributed to the 5%-per-year decline in stroke mortality since 1970.

From 1964 to 1984, coronary heart disease mortality declined 40%, and stroke mortality declined 55%.

Special Issues

High Risk Populations

The prevalence of hypertension (higher or equal to 140/90 or on antihypertension medication) among Blacks is 33% higher than among whites; however, severe hypertension (higher or equal to 115 diastolic) is 4 times as common among Black males as white males and 2 times more common among Black females than white females. The stroke mortality rate for Blacks is nearly double that for whites.

Steven Parker

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