Studies examine risk factors and potential consequences associated with prehypertension

Oct 25 2004

A substantial proportion of Americans have prehypertension (blood pressure above optimal levels, but not clinical hypertension) which is associated with an increased prevalence of other risk factors for heart disease and stroke and is also associated with potential increased risk for hospitalization and death, according to two articles in the October 25 issue of The Archives of Internal Medicine, one of the JAMA/Archives journals.

Hypertension (high blood pressure) affects an estimated 50 million Americans and contributed to approximately 251,000 deaths in 2000. Only approximately 34 percent of people with high blood pressure have it controlled, the articles state. Individuals with blood pressure above optimal levels, but without clinically defined hypertension are said to have “prehypertension” (systolic pressure of 120-139 millimeters of mercury or a diastolic blood pressure of 80 to 89 millimeters of mercury) and are at an increased risk of developing hypertension and are more likely to have other heart disease and stroke risk factors, according to background information in the articles.

Kurt J. Greenlund, Ph.D. from the National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, and colleagues analyzed data from 3,488 patients aged 20 years and older with blood pressure readings recorded during the 1999-2000 National Health and Nutrition Examination Survey. Cholesterol levels, diabetes mellitus, smoking status, proportion who are overweight or obese, and the presence of other risk factors were compared among patients based on blood pressure groups: normotensive (normal blood pressure), prehypertensive, and hypertensive.

Of the patients studied, 39 percent were normotensive, 31 percent were prehypertensive, and 29 percent were hypertensive. The prevalence of prehypertension was greater in men (39 percent) than in women (23.1 percent). Additionally, African Americans aged 20 to 39 years had a higher prevalence of prehypertension (37.4 percent) than whites (32.2 percent) and Mexican Americans (30.9 percent), but their prevalence was lower at older ages because of a higher prevalence of hypertension. The researchers also found that patients with prehypertension were 1.65 times more likely to have at least one other risk factor than patients who were normotensive.

“The greater prevalence of risk factors in persons with prehypertension vs. normotension suggests the continued need for early clinical detection and intervention of prehypertension and comprehensive preventive and public health efforts,” the authors write.

In another article in the same issue of The Archives of Internal Medicine, Louise B. Russell, Ph.D., of Rutgers University, New Brunswick, N.J., and colleagues used data from the first National Health and Nutrition Examination Survey (NHANES) Epidemiological Followup Study, to develop a simulation model to estimate the effects of prehypertension and residual hypertension (hypertension controlled by medications but not lowered to levels under 140 millimeters of mercury) among U.S. adults aged 25 to 74 years old who participated in the third NHANES survey (NHANES III; n=12,841).

The NHANES surveys collect information about risk factors and health outcomes including blood pressure, diabetes, obesity, diet and exercise, for various samples of Americans. NHANES III took place between 1988 and 1994.

The researchers found that except for women aged 25 to 45 years old, more than a third of each of the three age groups (25 to 44 years; 45 to 64 years; 65 to 74 years) in NHANES III had prehypertension. About two-thirds of the participants aged 45 to 64 years and 80 percent of participants aged 65 to 74 years had prehypertension or residual hypertension.

The researchers also found that “Together, prehypertension and residual hypertension accounted for 4.7 percent of hospital admissions per 10,000 adults aged 25 to 74 years, 9.7 percent of nursing home admissions, and 13.7 percent of deaths. Prehypertension alone accounted for 3.4 percent of hospitalizations, 6.5 percent of nursing home stays, and 9.1 percent of deaths,” the authors write.

“Our results confirm the substantial public health consequences of prehypertension,” the researchers conclude. “If prehypertension were eliminated, hospitalizations, nursing home admissions, and premature deaths could decline substantially.”

In an accompanying editorial, Martha L. Daviglus, M.D., Ph.D., and Kiang Liu, Ph.D., of the Feinberg School of Medicine, Northwestern University, Chicago write, “In this issue of the ARCHIVES, Greenlund et al and Russell et al report findings and projections from national samples on the consequences of prehypertension. Greenlund and colleagues find that approximately one third of adult Americans have prehypertension and that this adverse blood pressure level is accompanied by unfavorable levels of other major cardiovascular disease risk factors.”

“Not unexpectedly, Russell et al, using a statistical model relating coronary heart disease risk factor levels to rates of hospitalization, nursing home confinement, and death in U.S. adults aged 25 to 74 years, estimate that elimination of prehypertension and residual hypertension would result in noticeable percent decreases in these events,” the editorialists write.

“Although interest in population studies triggered by a new classification for a major cardiovascular disease risk factor is certainly timely and important, the key message of these findings is not new,” they write. “Concern about the effects of intermediate levels of a single risk factor may obscure the fundamental point: the national policy on cardiovascular disease prevention must focus on prevention and control of all risk factors simultaneously and on lifestyle approaches from conception, infancy, childhood, and youth on to reduce population cardiovascular disease risk to endemic, rather than current epidemic, levels,” conclude the editorialists.