In the recently published Seventh Report of the Joint NationalCommittee on Prevention, Detection, Evaluation, and Treatment ofHigh Blood Pressure (JNC 7), a new category, called "prehypertension,"was added in the classification of blood pressure (BP). What was therationale for this addition?
Q:In the recently published Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), a new category, alled "prehypertension," was added in the classification of blood pressure (BP).1 What was the rationale for this addition? A: The objective of identifying and treating hypertension is to reduce the risk of the morbidity and mortality associated with cardiovascular disease. A classification of BP in adults-although somewhat arbitrary-is useful to identify persons at high risk (based on BP and other factors) and to provide a framework for follow-up and treatment. A strong positive relationship between systolic blood pressure (SBP), diastolic blood pressure (DBP), and cardiovascular risk has long been recognized from observational studies such as the Framingham Heart Study and the Multiple Risk Factor Intervention Trial. As noted in previous JNC reports, this relationship is continuous, graded, consistent, independent, predictive, and etiologically significant for those with and without coronary heart disease. In the JNC 7 report, "normal" BP is defined as readings below 120/80 mm Hg. The old categories of normal and high normal have been combined to create the new category of "prehypertension," which designates an SBP of 120 to 139 mm Hg and/or a DBP of 80 to 89 mm Hg (Table 1). Why the change? The previous designation of "normal" BP was misleading, because for persons aged 40 to 70, each increment of 20/10 mm Hg doubles the risk of cardiovascular disease across the entire BP range from 115/75 to 185/115 mm Hg. Likewise, when patients were told they had "high normal" BP, they interpreted this to mean that they were not hypertensive. Yet those with BP between 130/80 mm Hg and 139/89 mm Hg are twice as likely to progress to hypertension as those with lower BP values. Improving control rates. In the United States, rates of hypertension control (to below 140/90 mm Hg) have improved modestly to 34% from 27% at the time of the last JNC Report (JNC VI), in 1997. Current control rates are still well below the Healthy People 2010 goal of 50%. The responsibility for improving control rates rests with both patients and clinicians. Patients must be motivated to meet target BP goals and adhere to therapy, and they must understand that optimal control will likely require 2 or more antihypertensive agents. Clinicians must educate their patients and establish the trust required to maintain patient motivation. They must also be willing to treat aggressively to achieve and maintain optimal recommended control rates. The classification of prehypertension introduced in JNC 7 acknowledges the relationship between elevated BP and cardiovascular disease and signals the need for further awareness and action on the part of both health care professionals and the public to prevent hypertension. Therapeutic strategies. The recommended management strategies include lifestyle modification for prehypertensive persons who do not have other major compelling indications for drug therapy (evidence of target organ damage or diabetes) (Table 2). It is hoped that increased awareness of the cardiovascular risks at levels of BP below 140/90 mm Hg will encourage more active and aggressive lifestyle modification in an effort to prevent progression to sustained hypertension. Drug therapy is recommended for prehypertensive persons with an SBP of 120 to 139 mm Hg or a DBP of 80 to 89 mm Hg who have other compelling indications for pharmacologic management. Finally, the JNC guidelines do not represent mandates but rather recommendations to assist clinicians in implementing prevention and treatment strategies for hypertension.